ENGLISH TRANSLATION OF MANUAL ON SOVIET SON-9 FIRE-CONTROL RADAR

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A031400010001-1
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 577
• Document Creation Date: December 23, 2016
• Document Release Date: September 19, 2013
• Sequence Number: 1
• Publication Date: March 6, 1964
• Content Type: REPORT

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CENTRAL INTELLIGENCE AGENCY
This material contains information affecting the National Defense of the United States within the meaning of t_e?Jszplunitge-gsvirsuie--
18, U.S.C. Secs. 793 and 794, the transmission or revelation of which in any manner to an unauthorized person is prohibited by law.50X1
S-E-C-R-E-T
COUNTRY
USSR! Poland
REPORT
SUBJECT English Translation of Manual DATE DISTR. 6 March 1964
on Soviet SON-9 Fire-Control
Radar NO. PAGES 2
REFE7h1rFc
DATE CW
INFO.
PLACE &
DATE ACC).
'anis UNEVALUATED INFORMAIIUN. JUUK(...t l7KALPIr4OJ AIM toe, los I1M
r-
1. Attached for retention is a two art manual on the Soviet SON-9 (FIRE 50X1-HUM
CAN) radar. The document entitl d Antiaircraft Artillery Instructipp..),
Gun-Laying Radar SON-91 is an Engli'Fitt translation of a Polish--language
manual published by the Ministry of Njational Defense, Warsaw) 1957.
2. Part I (310 pages) is entitled "Design and FUnctiLrTing of the SON-9
Radar" and Part II (263 pages) is entitled "Operati On 1/2)f the SON-9
Radar". A detailed table of contents is given at th? end of each
part.
50X1-HUM
(Note: Field distribution indicated by "#".)
?
50X1-HUM
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50X1-HUM
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S,E-C-R-E-T
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Distribution:
ARMY/FSTe
:
(1)
(w/Att)
NSA
:
(1)(w/Att)
STATE
:
(w/o Att)
AIR
:
(1)
(w/Att)
OSI
:
(1)(w/Att)
ONE/EE
:
(w/o Att)
AIR/FTD
(1)
(w/Att)
aRR/MIL
:
(1)(w/Att)
OCl/MIL
(w/o Att)
DIA
:
(1)
(w/Att)
NAVY
:
(w/o Att)
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MILITARY/AIR
22E-1 ya,..qual: "Gun-Laying Radar SON-9"
MINISTRY OF NATIONAL DEFENCE
SECRET
50X1-HUM _
Copy no.........
ANTI-AIRCRAFT ARTILLERY INSTRUCTION
GUN-LAYING RADAR SON-9.
Part I - Design and functioning of the set.
Part II - Operation of the set.
WARSAW
1957
50X1 -HUM
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INTRODUCTION
The SON-9 radar station is a complicated piece of equipment. A
thorough knowledge of the equipment as well as correct operation and
maintenance will ensure trouble-free operation and extend its service
life.
The first part of the Manual gives a general description of the station,
and construction of equipment and units.
The second. part contains instructions on the technical operation of the
station, tuning and adjustment of its equipment and units, maintenance 'and
care, fault-finding and repair procedure. Voltage and resistance charts and
oscillograms of voltages in reference points of the units are also given.'
The appendices include the list of spare parts (ZIP), the table of
electric vacuum devices,- description of the URAL-2 device, specification to
key diagrams of the units and,a table of transformer and choke data.
Key diagrams of separate systems, devices and units of the station,
diagrams of interunit connections, cables, a block diagram of the station
and all appendices are given in the Album, which is part and parcel of the
Manual.
References for diagrams and appendices appearing in the Album are given
in brackets (See Album or drawing).
PARTI
DESIGN AND FUNCTIONING OF RAZAR STATION SON-9
ChapterI
GENERAL
1. PURPOSE OF STATION
The mobile gun laying radar SON-9 in conjunction with fire-control
director PUAZO-6 (or PUAZO-5) is designed for use with small and medium
calibre anti-aircraft artillery. The SON-9 can be used also with PUAZO-3
.../or HJAZO-49
50X1 -HUM
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or PUAZO-41 but in these cases computor LSPPM must be used.
The SON-9 detects air targets at a distance of not less than 50 km.
irrespective of visibility and weather, continuously determines target
co-ordinates (azimuth, elevation angle and slant range) and transmits them
to the fire-control director and the searchlight.
The S0N-9 station during combat operation includes a trailer with radar
equipment and a tractor (truck ZIS-151), on which is mounted a power unit
of the APG-15 type, spares and other equipment.
The general view of the station with the tractor in a travelling position
is shown in Fig.1, and in a set-up position - in Fig.20
2. BASIC SPECIFICATIONS OF STATION
The station enables targets to be detected and tracked irrespective
of visibility and weather conditions.
The main specifications of the station are as follows:
1. Frequency range: 2700 to 2860 Mc/sec. (10.5 to 11.1 cm).
2. Power in the pulse: about 250 kW.
? 3. Detection range during manual sectol, scanning of a medium bomber
(Type Tu-2) flying at an altitude of 4000 me is not less than 50 km.
4. Range of automatic tracking of a medium bomber (Type Tu-2) is not
less than 35 km.
5. Limits of operation:
in azimuth unlimited
in elevation angle from -0-50 to +14-50
6. Mean error in determining target data during automatic tracking:
in range 20 m. within I - 35 km.
0-01.6 within 60-00 at elevation
in azimuth
in elevation
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angle values from +1-00 to +13-00
0-02 within +1-00 to 13-00
.../7. Resolution
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7. Resolution of the radar station in slant range:
during manual tracking ........ 125 m.
during automatic tracking 200 m.
8. Type of antenna . .... ....... . parabolic reflector (D = 1.5 m.)
with asymmetrical rotating dipole
9. Half-power width of the directional radiation pattern: 0-83 - 0-08
10. Pulse duration; 0.5 microsecond.
11. Pulse repetition frequency; 1875 c/sec.
12. Intermediate frequency; 30 Mc/sec.
13. Intermediate frequency amplification in the range measuring channel;
not less than 75,000.
1.4. Intermediate frequency pass-band width: 3.6 Mc/sec.
15. Intermediate frequency amplification in the automatic tracking
channel; not less than 2009000.
16. Intermediate frequency pass-band width in the automatic tracking
channel: 2.2 to 2.8 Mc/sec.
17. Supply voltage;
single-phase current ..?. OOOOOO 110 V, 427 c.p.s.
three-phase current ....... 220 V, 50 c.p.s.
18. Power consumed fromg
110 V, 427 c.p.s. mains, 2900 VA
220 Vy 50 c.p.s. mains 7000 VA
19. Sector scanning:
in azimuth ........... 4-00 - 9-00
in elevation angle 1-70 - 2-10
20. Radar siting time ... 15 min.
21. Connection time cf sited radar 3.5 min.
22. Weight of radar trailer approximately 7 tons
23. Weight of complete tractor- approximately 8 tons
.../24. 'Dimensions
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24. Dimensions of trailer, cabin in travelling position:
length with a drawbar 6500 mm
length without a drawbar 5000 mm
height 3200 mm
width ........ ..... 2400 mm
25. Maximum transportation speed:
on main roads 40 km/hr
on country roads 25 km/hr
26. The station may be transported by railways with freight dimension
3, SIMPLIFIED BLOCK-DIAGRAM OF STATION
AND PRINCIPLE OF DETERMINING COORDINATES
?011.
The station produces powerful short-time electromagnetic pulses of high
frequency, which are radiated into space by the antenna.
If the beam of electromagnetic energy strikes an object, for example
an aircraft, on its way, a portion of this energy will be reflected back to
the station.
The reflected pulses picked up by the antenna are furnished to the
receiving equipment through the feeder system.
The pulses converted and amplified in the receiving system are fed to
the cathode-ray tubes of indicators, forming corresponding target marks on
their screens, as well as to the antenna positioning system and automatic
range finder (during automatic tracking) which ensure continuous matching
of the antenna axis with the direction to the selected targetand automatic
determining of the slant range and the target angular data.
The equipment of the SON-9 has the following basic systems (See Fig.3):
(a) transmitting system;
(b) antenna-feeder system;
(o) receiving system;
(d)
range-measuring system;
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.../(e) plan-positon
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'(e) plan-position indicator system;
(f)
antenna positioning system;
(g) data transmitting system;
(h) power supply system.
The transmitting system is designed to produce powerful short-time
electromagnetic pulses of high frequency which are radiated into space by
.,be antenna.
The transmitting system includes a driver unit and a modulator-
oscillator unit composed of a modulator, a magnetron oscillator and a
high-voltage rectifier.
The driver is fed with trigger pulses produced in the range finding
system. These pulses are of about 1.5 microsecond duration and of
1875 o/sec repetition frequency.
The trigger pulses are used in the driver to generate voltage pulses
of 0.5 microsecond duration which are amplified and furnished to the
modulator. Here they are converted into powerful high-voltage pulses with
an amplitude of about 20 kV and are fed out to the magnetron.
The magnetron produces powerful pulses of electromagnetic oscillations
of 0.5 microsecond duration and of 1875 c/sec repetition frequency. The
oscillation frequency depends upon the type of the magnetron employed in
the station and is in the range of 2700 to 2860 Mc/sec.
The station is provided with magnetrons, types M1-18, M1-19, M1-20
and M1-21. Power of oscillations during the pulse is about 250 kW. The
oscillations produced by the magnetron are furnished to the antenna-feeder
system.
The antenna-feeder system is designed to transmit electromagnetic
energy generated by the transmitter, radiate it into space in the prescribed
direction as well as to pick up signals reflected from the target and apply
them to the receiver input. The station uses one antenna for transmitting
and receiving.
?SECRET
.../The antenna-feeder
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The antenna-feeder system includes: a high-frequency coaxial feeder, an
antenna change-over switch and an antenna consisting of the antenna head and
a parabolic reflector.
Energy of high-frequency oscillations produced by the magnetron
oscillator is supplied through the feeder to the antenna head and a radiator
situated in the focal plane of the parabolic reflector. In intervals
between the transmitter pulses the echo signal energy is applied through the
same feeder from the antenna head to the input of the receiving system. To
facilitate the antenna rotation the feeder line is provided with rotating
joints arranged on those feeder sections that run along the appropriate
rotation axis of the antenna.
The antenna change-over switch performs the following two functions.
When the magnetron oscillator is operating it blocks the path of powerful
pulses from the magnetron oscillator output to the receiver and ensures
practically complete transmission of radiofrequency energy from the magnetron:
oscillator to the antenna. In intervals between the transmitter pulses when
signals reflected from the targets return to the station it ensures complete
transmission of energy of these signals from the antenna to the receiver in-
put thus preventing useless dissipation of this energy in the transmitter
circuits.
The station antenna due to the use of the parabolic reflector of 1.5 m
diameter possesses sharp directivity both during transmission and reception.
This means that during transmission its energy is radiated in a narrow sector
of space and during reception of electromagnetic oscillations the antenna is
fed with the signals from those targets which are within the same sector.
The main characteristic of any directional antenna is its diagram or
so-called radiation pattern which represents graphically power distribution
during antenna radiation in various directions during transmission and
.../sensitivity of
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sensitivity of an antenna to the signals cOming from various directions
during reception.
The width of the radiation pattern of the SON-9 antenna is 0-83. It is
determined as an angle between two directions, the radiating power for which
constitutes half the power in relation to its maximum radiation (See Fig.4).
To provide accurate continuous tracking of the target during automatic
tracking the axis of the radiation pattern (i.e. the direction of maximum
radiation) is displaced with respect to the geometrical axis of the antenna
(the axis coming through the focus and geometrical centre of the paraboloid)
through an angle of 0-23 (Fig.5) and the entire radiation pattern, when
the station ie functioning, is continuously rotated about the geometrical
axis of the antenna at a speed of 1440 r.p.m. (24 r.p.s,). In this case
the axis of the radiation pattern describes a cone in space. The antenna
geometrical axis coincides with the electrical axis of the antenna during
automatic tracking in angular coordinates (the antenna ?electrical axis - the
direction from the antenna to the target being tracked at accurate bearing of
the target).
The axis of the radiation pattern is displaced in relation to the
geometrical axis of the antenna due to the radiator asymmetry and the
radiation pattern rotation is achieved by rotating the antenna head about its
axis with the help of an electric motor which simultaneously rotates a
reference voltage generator (GON) included in the antenna positioning System.
The receiving system is designed for converting the signals reflected
from the target and picked up by the antenna and for further amplification
to the value required for normal operation of the range and plan-position
indicators, the antenna positioning system and the automatic range finder
unit.
The receiving system consists of crystal mixers of the signal,
automatic frequency control (AFC), an intermediate-frequency preamplifier
(IFP) and an amplifier of the range- and automatic tracking channel.
trNLT" ,../The receiving
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The receiving system employs a superheterodyne circuit.
The reflected signals picked up by the antenna are furnished through
the feeder line and the antenna change-aver switch to the crystal mixer
which is continuously fed with A.C. voltage of high frequency from the
centimetre heterodyne (klystron) located in the intermediate-frequency
preamplifier stage. The heterodyne frequency is higher than that of the
transmitter, i.e. the frequency of the picked-up signals by 30 Mc/sec.
Simultaneous action of these two high-frequency voltages on a non-
linear element, i.e. the crystal mixer, results in development of intermediate
(differential) voltage of 30/1c/sec frequency at the mixer output. Each
intermediate frequency pulse duration is the same as the incoming pulse
duration, and equals 0.5 microsecond.
From the crystal mixer the I.F. pulse voltage is applied to the I.F.
preamplifier through the radio-frequency cable. This voltage is amplified
in the preamplifier by three stages and through the radio-frequency cable
is applied to the-input of the automatic tracking channel amplifier. Here
the signals are amplified first in one common interwediate frequency
amplifier channel (four stages) and then in two amplifier channels - in range
and automatic tracking channels. From the output of the automatic tracking (
channel the signals are coupled to the automatic tracking unit of the antenna
positioning system, while from the range channel - to the input of the range
channel amplifier unit of the receiving system.
All signals which are being furnished to the input of the receiving
system are amplified in the amplifier unit of the range channel. The
amplifier output is coupled to the range and very narrow gate indicators
plan-position indicator system and to the automatic range finder unit to
control its operation during automatic measurements of the slant range to the
targets. The range and plan-position indicators are devised to observe the
signals reflected from all targets and local objects that are at the given
moment within the area swept by the antenna.
SECRFT .../The receiver
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The receiver automatic tracking channel is completely cut off most of
the time. It is opened only at the time of arrival of the signals reflected
from the target selected by the operator.
The signals reflected from the target are passed from the output of the
automatic tracking channel amplifier to the antenna positioning system which
by the action of these voltage pulses provides continuous automatic matching
of the antenna axis with the direction to the target being tracked.
The automatic frequency control circuit in the I.F. preamplifier unit
1110 produces Voltages which control the klystron frequency in such a manner that
when the difference betWeen the klystron and magnetron frequencies deviates
from 30 Pc/sec, the klystron frequency changes automatically and the dif-
ferential (intermediate) frequency remains constant. This compensates for
unstability of the klystron and magnetron carrier frequency and ensures
constancy of the receiving system sensitivity.
The range measuring system is designed to measure the target range
continuously and accurately and to synchronize the operation of other systems
and units of the station.
The range measuring system is composed of the following components a
range and very narrow gate indicator unit, a range unit an automatic range
finder units a range mechanism unit.
The range measuring system is supplied from two common supply units for
the range measuring system and the plan-position indicator system.
Determination of the slant range, i.e. measurement of the time interval
between the emission of the signal and receipt of the corresponding echo is
achieved by aligning the reflected signal with electronic markers whose time
delay in relation to trigger pulses can be determined with a high degree of
410? accuracy.
Having matched the electronic markers with the echo pulse on the cathode-
ray tubes of the range indicator unit, the operator can read the target slant
range off the scales of the range mechanism unit.
ereirmi .../The range
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The range is measured with a moving target, therefore the continuous
matching of the electronic markers with the reflected signal is done
automatically with the help of the automatic range finder or manually by the
operator.
To synchronize the operation of all elements of the range measuring
system the plan-position indicator system, the transmitter and the range unit
Is provided with a sine-wave oscillator whose frequency (74.955 Kc/s) is
crystal controlled. The crystal oscillator voltage is applied to the step
divider circuit which produces voltages with frequencies five, twenty and
forty times smaller than the frequency of crystal oscillator, i.e.
approximately 15 Kc/s, 3.75 Kc/s and 1.875 Kc/s.
To obtain a circular sweep on the fine-range indicator use is made of
two sine-wave voltages having the frequency of the crystal oscillator,
shifted in phase by 90? in relation to each other. These two voltages
applied to two pairs of deflecting plates of the tube cause the electronic
beam to trace a circle on the tube screen. The time required for the beam
to make a circle is 13.3 microseconds, which corresponds to a range of 2 km.
To obtaina circular sweep on the coarse-range indicator use is made of
two voltages of 3.75 Kc/s which are 900 out of phase. The voltages applied
to the deflecting plates of the tube make the electronic beam trace a circle
on the screen; the time required for the beam to make a circle is increased
20 times as compared with the time required for the fine-range tube and,
consequently, corresponds to a range of 40 km.
The voltage pulses of 1.875 Kc/sec frequency produced in the range unit
are employed for forming trigger pulses which control the transmitter and the
pian-position indicator system. Besides, voltage of 1.875 Kc/sec frequency
is used for forming gate pulses whose delay in relation to trigger pulses can
be varied.
The transmitter sends its pulses of 1.875 Kc/sec frequency every two
revolutions of the sweep on the coarse-range indicator and every 40
.../revolutions of
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revolutions of the sweep on the fine-range indicator. ? The indicators are
set in such a position that each time the pulse is transmitted the electronic
beams in both tubes are in upper points of the sweep trace (at zero point).
The echo pulses are furnished from the output of the receiver range channel
to the central deflecting electrodes of both range indicators. These
pulses cause outward radial deflections on the sweep trace.
Thus the screen of the coarse-range indicator displays the station
transmitter pulses as a radial pip in the upper initial point of the sweep
trace, whereas radial pips caused by the target echoes are arranged on the
sweep circle at corresponding distances from the transmitter pulse.
The echoes from the targets the range difference between which amounts
to 40 km. are located in the same point of the sweep. For example, the
echoes from the targets located at distances of 10 and 50 km. from the
station appear on the sweep trace on the 10 km, range mark after each
transmitter pulse during the first and second revolution of the sweep.
To avoid possible errors in determining the target range the sweep of
the coarse-range indicator is brightened by pulses generated in the range unit.
The gating pulse duration is approximately 260 microseconds, i.e. slightly
less than the time required for one revolution of the sweep on the screen of
the coarse-range indicator. Thus the indicator screen is brightened only
for the time of the first or second revolution of the sweep after each
transmitter pulse depeLding upon the position of the switch 0 - 40 km. -
- 80 km.
To form the electronic marker of the coarse-range indicator use is
made of strobe pulses which brighten an additional area on the sweep,
i.e. a movable electronic marker. To determine the range it is necessary
to match the movable electronic marker with the target echo by operating the
range knob and to read the indication on the coarse-range scale of the range
mechanism. However, the reading will be inaccurate because first, the
.../linearity in
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linearity in changing the strobe pulse delay depenina on the turn of the
range mechanism coarse scale is sufficiently high, and secondly, the
electronic marker fails to be matched accurately with. the target echo on
the coarse-range indicator due to its small scale.
To determine the range accurately provision is made in the system for
a second reference pulse - the electronic marker of the fine-range indicator
which is formed with the help of the crystal oscillator voltage. This
voltage is applied to a phase-shifting circuit. The main component of the
circuit is a phase shifter, whose rotor is kinematically connected to ..the
range mechanism fine scale. The change of -voltage phase at the phase shifter
output is linearly dependent upon the turn of its rotor, i.e. the turn of the
range mechanism fine scale. The crystal oscillator voltage shifted in
phase is used to form two short pulses whIch, applied to the fine-range
indicator, form two darkened sectors, or the fine-range electronic marker.
-When determining the range it is necessary to set the elect2onic marker
on the fine-range indicator symmetrically relative to the echo signal
selected on the coarse-range indicator, i.e0 to set in such a way, that the
end of the first and the beginning of the second mark of the electronic
marker are at the same level to the seep trace, then to take a reading' on
the range mechanism fine scale always rounding off the smaller values. ?
If the electronic beam of the fine-range indicator were visible all the
time, large errors might occur when determining, the range, because the same
sweep spot of the fine-range indicator would display the signals reflected
from several targets the distances between which differ from each other by
multiples of two kilometres. To avoid superimposing echo signals from
several targets the fine-range indicator is brightened by pulses of lower
than 13.3 microseconds duration, i.e. lower than the time required for one
revolution of the sweep.
For gating of the fine-range indicator use is made of strobe pulses.
As was mentioned above the strobe pulse delay in relation to trigger pulses,
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.../always corresponds
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always,corresponds to the reading on the range mechanism coarse scale. If
1111, the scale readings are increased from 0 to 40 km. by operating the range
knob, the strobe pulse delay in relation to trigger pulses will increase
from 0 to 266 microseconds.
Thus, depending upon the scale readings the strobe pulse brightens on
the fine-range indicator the portion of the first, second, third and so on
up to the twentieth sweep revolution inclusive after the transmitter pulse.
Consequently the screen of the fine-range indicator can display a signal
from that target which coincides with the electronic marker on the coarse-
range indicator and whose range corresponds to the reading on the range
mechanism scales.
When tracking the target its slant range is determined by continuously
matching the electronic markers with the target echo. The elements for
controlling the electronic markers are kinematically connected between each
411 other and have a common drive. Besides the manual range trackirg, when the
electronic markers are matched with the target echoes by rotating manually the
common drive with the help of the range knob, provision is made for automatic
tracking. In this case the common drive is rotated by the automatic tracking
motor whose speed is controlled by the automatic range finder.
The automatic range finder produces two pulses that follow in succession
(called split gate pulses) which are always synchronized with the reference
pulse - the electronic marker of the fine-range indicator. Besides, the
automatic range finder is furnished with the target echoes from the receiver
range channel output.
The time-phase of the echo signals and reference pulses is compared in
a special stage of the automatic range finder (called an error signal time
discriminator.) The voltage at the discriminator output depends on the
mutual time-phase of the reference pulses and the target echo. The
polarity of this voltage depends on whether the reference pulses lag
behind or lead the target echo, whereas its value is determined by the degree
of lagging behind or leading. RrpAric
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When the electronic markers are matched with the echo from the target
selected for tracking on the indicators, the reference pulses in the
automatic range finder are arranged symmetrically with respect to the echo
from the same target - there is no error voltage at the discriminator output.
This error signal in the course of automatic range tracking is aMplified
and-converted into an A.C. voltage of 50 c.p.s. this voltage controls the .
automatic tracking motor, the reference pulses in the automatic range finder
and electronic markers on the fine-range tube being arranged symmetrically
in relation to the echo from the target being tracked.
The common drive of the range meChanism is connected with coarse and
fine-range transmitting selsyns which aid in conveying continuously the
slant range data to the anti-aircraft fire director and other devices
situated outside the station.
To ensure tracking of the selected target in angular coordinates
(without interference from other targets located in close proximity) use is
made of short pulses of 0.3 microseconds duration called very narrow gate
pulses to control the operation of the receiver automatic tracking channel.
The time-phase of the very narrow gate pulses is always dependent upon the
position of the electronic marker on the fine-range indicator. When
matching electronic markers with the target echo on the range indicators, the
very narrow gate pulses open the gated intermediate-frequency amplifier stage
of the receiver automatic tracking channel at the moment the echo from the
selected target is applied to the receiver input.
Controlling the receiver automatic tracking channel by very narrow
gate pulses makes it possible to track the target without interference from
other targets which are within the antenna scanning area if the difference
between the slant ranges of these targets and the selected target exceeds
approximately 125 m.
The plan-position indicator system is designed to detect and observe
targets in the area being scanned as well as to determine their coordinates
emu .../with an
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with an accuracy sufficient for automatic target tracking.
The plan-position indicator system includes a plan-position indicator
unit and a plan-position indicator transmitting selsyn housed in the antenna
pedestal.
The plan-position indicator system is fed from the supply unit of the
range measuring and plan-position indicator systems.
The plan-position indicator utilizes a magnetic cathode-ray tube. The
tube deflecting coil passes saw-tooth current pulses. The magnetic field
induced by the current pulses causes the electronic beam to deflect from the
centre to the edge of the screen, thus forming a radial sweep trace. The
sweep is triggered by trigger pulses of 1.875 Kc/sec frequency produced in
the range unit. The same pulses are used for triggering the station
transmitter which synchronizes the moment of the sweep start on the plan-
position indicator screen with the emission of the transmitter pulse.
With the help of the synchro drive circuit of the deflecting coil the
position of the radial sweep changes depending on the antenna rotation angle
in azimuth. During continuous rotation of the antenna in azimuth, i.e.
during circular scanning, the radial sweep on the tube screen rotates in
synchronism with the antenna about the screen centre. During sector scanning
the radial sweep on the screen while moving in synchronism with the rotation
of the antenna in azimuth, oscillates in a definite sector.
From the output of the receiver range channel amplifier the echo pulses
are furnished to the control electrode of the cathode-ray tube, thus
increasing the brightness of the radial sweep in appropriate points. During
continuous circular rotation in azimuth bright spots from each given target
appear on the sweep only when the target is within the radiation area. As
a result the mark from the point target on the tube screen is essentially
an echo-arc formed by bright spots on the rotating sweep. The angle
subtended by the echo-arc equals the antenna pattern flare. The distance
.../between the
MAU.
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between the echo-arc and the tube screen centre given in a definite scale
_corresponds ,to, the slant range of the target,
At the edge of the tube screen is an azimuth scale with angular
divisions (from 0 to 60-00). Due to synchronous rotation of the sweep and
antenna in azimuth, the sweep always indicates an azimuth in which the
antenna is directed. The target azimuth is determined by .taking the reading
off the azimuth scale, which corresponds to the mid-point of the echo-arc
representing the given target.
In order to observe the signals returned from various targets in the
area surrounding the station the plan-position indicator utilizes a cathode-
ray tube with a long-persistance screen. Any bright spot appearing on the
ecreen retains visible for about 10 seconds. Thus during circular scanning
when the antenna rotates in azimuth at a speed of about 12 r.p.m. the tube
soreen continuously displays the target echoes and local objects.
The plan-position indicator unit is provided with a range marker stage
whose operation is controlled by voltage pulses of 15 Kc/s furnished by
the range unit. The range pulses create bright spots on theradial sweep,
which during continuous rotation merge into range concentric rings. The
distance between the adjacent range rings corresponds to 10 km. of slant
range.
The slant range of the target is determined on the screen of the plan-
position indicator by the position of the target echo in relation to the
range rings.
The antenna positioning system serves to cchtrol the antenna position,
which can be changed by rotating the antenna about the vertical axis
(rotation in azimuth) and about the horizontal axis (rotation in elevation).
The system permits the following three modes', ef operationto be used
(depending on. how the antenna positioning iS'carried out)- automatic
circular or sector scannings Manual control and automatic target tracking..
..,/The first
SEC
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The first mode of operation is used to observe the area surrounding the
station on the P.P.I. or in a selected sector.
The second mode of Operation is Used to control manually the antenna
Position, to orient the antenna by the target designation data and to follow
the target before changing over to autotatic tracking.
The third mode of operation ig Used to determine accurately the
coordinates of the target being tracked. In this case the azimuth and
elevation angle are determined automatically, but the range - automatically
or manually.
Besides, provision is made in the station SON-9 for reception of
target designation data from the circular scanning station and for remote
control of the antenna position from the anti-aircraft fire director PUAZO-6.
In the latter case the antenna rotates in synchronism with the sighting
column of the anti-aircraft fire director PUAZO-6 while the target range is
111 determined by the station automatically or manually.
During circular (or sector) scanning the antenna can rotate((or
oscillate) in azimuth with tilting up and down of the antenna in elevation,
as well as at constant elevation which is set by the operator.
During manual control the antenna may be controlled in azimuth and;
elevation with the help of handwheels.
During automatic tracking the antenna automatically follows the target
when its angular coordinates are changed.
The antenna positioning system is composed of the following units and
assembliesl
1. An automatic tracking unit.
2. An azimuth and elevation tracking unit.
3. An antenna control unit.
4. Amplidynes EMU-5.
5. Azimuth and elevation drive motors.
.../6.. An antenna
SECRET
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6. An antenna pedestal.
7. A supply unit of drive-motor field windings..
8. A reference voltage generator (GON).
During automatic tracking use is made of the equisignal zone principle
which consists in the following.
As was mentioned above the antenna radiation pattern (direction of
maximum radiation) is deflected from the'antenna geometrical axis by an angle
of 0-23.
When the station is functioning the antenna head and consequently, the
radiation pattern are continuously rotating about the geometrical axis at a
speed of 24 r.p.m. In this case the radiation pattern axis describes a
cone in space. During rotation of the antenna head the point of intersection
of the radiation pattern with an imaginary plane passing through the target
and at right angles to the antenna geometrical axis (the so-called image
plane) will move along the circumference as sho*n in Fig.6. The same figure
represents four typical position S of the radiation pattern; extreme top,
right, lower ,and left positions. .)oints A, B, C, and D are respectively
the points of intersection of the radiation pattern axis with the image
plane for these four positions of the pattern.
If the target is in point 05 i.e. on the antenna geometrical axis, then
at any position of the radiation pattern the value of the signal reflected
from this target remains constant and proportional to section ab on the
radiation pattern. Therefore the direction to point 0 is called the
direction of equisignal zone or electrical axis of the antenna. Fig.7, a
shows voltage pulses of the target echoes.
If the target moves from point 0 to point C (See Fig.6) the value of the
target echoes depends upon the position of the radiation pattern rotating in
space at a speed of 24 r.p.m. The value of the target echoes is maximum in
the case when the radiation pattern axis is deflected from the antenna
/electrical axis
SECRET
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- 20
electrical axis (equisignal direction) towards the target displacement
(direction OC). The value of the target echoes is minimum when the
radiation pattern axis is deflected from the antenna electrical axis in the
direction opposite to the target displacement. Thus when the radiation
pattern rotates, the value of echoes changes with a frequency of 24 c.p.s.
(Fig.7, b).
The magnitude of the echo variation (modulation factor) is proportional
to the antenna deflection from the direction to the target or to the so-called
sighting error b. Thus if there is a sighting error, the echo signals are
modulated. These signals are picked-up by the antenna, amplified by the
receiver and are detected. As a result low-frequency A.C. voltage is
obtained which varies with the modulation frequency of the echo signals
(24 c.p.s.). This voltage is called the error voltage.
Thus, if the antenna is pointed exactly at the target the echo signals
will not be modulated (Fig.7, a) and after they have been detected the error
voltage will be zero. The amplitude of the error voltage is proportional
to the value of the sighting error while the phase (in relation, for instance,
to the moment the beam passes through the extreme left-hand position when it
is rotated in space) characterizes the magnitude of the target deflection in
azimuth and elevation.
If the error voltage phase equals 0 or 180? the target is deflected
only in azimuth.
If the phase of this voltage equals 900 or 270?, the
target is deflected in elevation. At intermediate values of the error
voltage phase the target is simultaneously deflected in azimuth and elevation,
the more the phase differs from zero or 1800 the more the deflection of the
target in elevation and the less in azimuth.
In order to aim the antenna at the target (to align its geometrical
axis with the direction to the target), it is neoessary to turn the antenna
in azimuth through angleN3 (in the inclined plane) and through angle.kz
SECRET .../in elevation
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?
?
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in elevation (Fig.6). To rotate the antenna, the drive motors rotating the
antenna in azimuth and elevation should be fed with control voltages
proportional to deflections in azimuth AP and elevation AE, respectively.
Therefore the error voltage should be divided into two components so that
the amplitude of one is proportional to the value of the target deflection
in azimuth AP while the amplitude of the other component - to the value of
the target deflection in elevation Pe.
The error voltage is divided into the two components in the azimuth and
elevation tracking unit by means of two voltages produced by the reference
voltage generator.
The reference voltage generator is directly coupled to the electric
motor rotating the dipole and develops two voltages shifted in phase by 90?
in relation to each other (Fig.8). The frequency of these voltages as well
as that of the error voltage is determined by the speed of the dipole rotation
and amounts to 24 c.p.s.
The error voltage and reference voltages are simultaneously applied to
the commutator stages of the tracking unit to produce two control voltages.
One voltage, i.e. azimuth voltage, is atained as a result of inter-
action of the error voltage and azimuth reference voltage (Fig.9); the
voltage is dependent on that component of the error voltage which has been
obtained due to the target displacement in azimuth through angle a.
The second voltage, i.e. elevation voltage, is obtained as a result of
interaction of the error voltage and elevation reference voltage (Fig.9)
the voltage is dependent on that component of the error voltage which has
been obtained due to the target displacement in elevation through angle ,A,6 .
The control voltages are amplified in the amplification and amplidynes
and after that are applied to the drive motors rotating the antenna in
azimuth and elevation.
The direction the drive motors are rotating is such that with the
error voltage applied the antenna moves in the direction of the target,
SIAURT "until its
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until its geometrical axis is aligned with the target direction. Then the .
411 error signal equals zero and so do the control voltages.
Mien the target moves the error signal appears again, control voltages
will be developed in the azimuth and elevation channels and the drive
motor will move the antenna again toward the target.
During continuous movement of the target the radar antenna will
automatically follow the target.
During manual control the azimuth and elevation channels are fed with
two independent error voltages produced by selsyn-transformer circuits.
The azimuth channel is supplied with error voltage produced by the
transmitting selsyn and the azimuth selsyn-transformer whereas the elevation
channel with error voltage produced by the transmitting selsyn and the
elevation selsyn-transformer. Instead of two reference voltages from the
reference voltage generator the both channels are fed with one common
voltage of 50 c.p.s. obtained from the station supply circuit.
The azimuth and elevation transmitting selsyns are accommodated in
the antenna control unit and are kinematically coupled with the appropriate
controls situated on the front panel of the unit. By rotating these
controls the operator can create independent error voltages and,
consequently, move the antenna in azimuth or elevation.
The searching differs from the manual Control operation in that the
transmitting selsyns of the antenna control unit are not rotated manually
with the help of handwheels but are driven by:the motor housed in the
antenna control unit, Rotation from this motor may be imparted to either
the azimuth transmitting selsyn or simultaneously through a special set of
gears to the elevation transmitting selsyn.
The operator, sets the position of the azimuth and elevation scanning
111 sectors with the help of azimuth and elevation handwheels of the antenna
control unit.
?
?
SECRET
.../The data
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eiretnrY
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p? n
The data transmitting system is designed for automatic continuous
transmission of the target data produced by the station to the station
display units, anti-aircraft fire director PUAZO-6 and other receivers
which may be located outside the station. In addition, the system
includes a number of components which make it possible to receive the
target designation data from the outside equipment (from the warning station,
anti-aircraft fire director PUAZO-6).
Power supply system. The station is supplied from a power unit, type
APG-15, with A.C. voltage of 220 V5 50 c.p.s. and A.C. voltage of 110 V,
427 c.p.s.
In addition the station can operate from the three-phase 220 Vy
50 c.p.s. mains. In this case 220 V, 50 c.p.s. are fed to the station
through the commutation circuits of the power unit, whereas 110 V, 427 c.p.s.
are produced by the generator mounted on the unit, the generator being
supplied from three-phase 220 V A.C. mains.
4. STATION DESIGN
The equipment of the SON-9 station, is mounted in the trailer body
(Fig.10) which is towed by a ZIS-151 truck. The trailer body has a two-
sided door on the right side, a horizontally hung rear door, and two windows
on the right and left sides of the body. The front wall has a hatch
through which an automatic air dryer is installed. The top of the body
carries a dome which covers the antenna when the station is in travelling
position. When the station is set-up, the dome is removed, from the body
top and its halves are placed near the station.
The trailer chassis is provided with pneumatic brakes actuated from the
truck. For levelling the trailer, the chassis is equipped with four jacks.
The body has lighting, a stove and ventilation.
The rear part of the body accommodates control desk 18 (See Fig.10)
,which incorporates several units, Located to the right of the control desk,
.../above the ?
SECRET
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wiDLyeL I
above the wheel house frame, is a control unit, while to the left of the
control desk the locker for spare parts, tools and accessories (ZIP) and a
voltammeter AVO. Under the control desk is located control panel 20. The
front part of the body houses transmitter cabinet 5 with a high-voltage
rectifier and antenna pedestal 6, arranged on it. The cabinet for amplidynes
2 and 3 is installed above the left-hand front wheel house frame. The rack
mounts air dryer 4. At the front wall transmitter cooling fan 1 is mounted
on the floor.
To the right of the entrance door on the body wall are fire
extinguishers and a lighting board.
On the left-hand body wall under the window is fixed receiving selsyn
unit 169 to the right of the window is stove 15. Between the stove and the
amplidyne cabinet on the body wall are located: an echo box, below is a
bracket with antenna heads, closer to the stove is the radar operator's
folding chair 14 and the telephone operator's chair. The bracket under the
telephone operator's table mounts telephone set 21. Built into the left-hand
body wall are outer connection boards 24 of the station. The equipment whose
operation is affecteu by jolting during transportation (main control desk,
control unit, echo box) is mounted on rubber shock absorbers.
The main control desk (Figs 11 and 12) is built in the form of a cabinet
which houses the various units.
The units are secured to the control desk with the help of special
retainer bolts. To prevent insertion of a unit into a wrong compartment
provision is made for mechanical interlocking.
The front panels of the units carry control and tuning elements (knobs,
screw-driver operated shafts, switches, test jacks, etc.) as well as
indicators which aid in checking the operation of the station. The units
are connected with the help of knife-type connectors.
All connecting wiring arranged on the back of the unit is covered by
three removable shields located on the rear side of the frame. The units are
marked with corresponding numbers.
nrs-ariarv ..../Tho transmitting
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The transmitting system is mounted on retractable chassis which is
110 pushed into transmitter cabinet 5 (See Fig.10).
The transmitter cabinet is reinforced welded structure with a top-
mounted steel plate which carries the antenna pedestal. The cabinet is
designed as a base for the antenna pedestal.
The modulator-oscillator unit housing carries the driver unit and the
intermediate-frequency preamplifier unit of the receiving system. These
units are put into the modulator housing on the side of the front panel and
are held in place in the same way as the main control desk units. The
modulator-oscillator unit housing is mounted on skids which facilitates its
withdraw'.
The modulator-oscillator unit housing is bolted on to the rear part
of the transmitter cabinet.
The chassis is cushioned by means of shock absorbers.
The right-hand upper corner of the housing accommodates the magnetron,
the antenna change-over switch and the magnetron heater transformer.
The magnetron and the antenna change-over switch are secured on a
1111 common plate which is rigidly bolted on to the antenna pedestal foundation.
The transmitter components are cooled by exhaust fan 1 located in the
trailer body behind the transmitter. The magnetron and modulator valves are
cooled by the air forced by the fan located inside the transmitter. To
provide free access to all transmitter units the cabinet plating is provided
with six small doors. In addition the panel covering the magnetron is
hinged. Protection of personnel against high voltage is achieved by
interlocks mounted on each hinged door and the relay of the transmitter
cabinet.
The amplidynes are located above the left-hand wheel house frame in the
cabinet.
To reduce noise the cabinet is covered with a sound proof shield which
is screwed to the cabinet. For cooling the amplidynes the front body wall
is provided with a vent hole.
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.,- 26 7
Mounted above the left-hand rear wheel house frame is a'etorage battery
110 supplying the emergency lighting circuit of the trailer body.
?
?
5. LIST OF STANDARD EQUIPMENT
The Table below lists a number of units and assemblies included in the
station standard equipment and their designation.
Name of unit
Designation
Transmitting System
Driver unit ............?..............................?....
Modulator-oscllator unit ...................................
Receiving System
Intermediate-frequency preamplifier ....... ..... .......
Automatic tracking channel amplifier unit ...... ....... ......
Range channel amplifier unit ....... ........... 000000000
Antenna-Feeder System
Antenna change-over switch 0000000000000000000000000000000000
Feeder system, .......................... ...... ...............
Range-Measuring System
Range unit ..000000000 000000000000000000?0?00?00000000 0000000
Range-mechanism unit .000 0000000" 01011, 0000 00000 *easels" one
Range and very narrow gate indicator unit
Automatic range finder unit ........ .............. a. .o a 0 .....
Plan-Position Indicator System
Plan-position indicator unit a a a a a ..... a ...... ..............
Supply unit of plan-position indicator and range-measuring
systems 00000000 00000000000000 00?00?0?00000000000000000000
Range-measuring system supply unit ............. ..........
SERET
23
25
22
1
2
28
8
4
3
7
11
5
9
...Antenna Positioning
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Name of unit
! Designation
Antenna Positioning System
Automatic tracking unit OOOOOOOO 000000000 OOOOO 000000000000000
Azimuth and elevation automatic tracking unit OOOOOO
Antenna control unit 04000 OOOOOO 0000000000 OOOOOO 000000000000
Amplidyne cabinet . D?0?0?01" "OOP" 0000?0000 "0000" 00000OP
Supply unit of drive-motor field windings :..................
Antenna pedestal .............................-...?... 000000041
Data Transmitting System
Receiving selsyn unit OOOOO ........ OOOOOOOO 0000000000000000 00
Outer board 000000000000000000000000000 OOOOOO 0 OOOOOOOOOOOO 000
?12221Z_Lattli
Control Unit 0?000000000000000?000?0?0000?0000000000000000000
Control panel OOOOOOO 00000000 OOOOOOOO '00000 OOOOOOO 0OOOOOOOOO
6
10
12
66
32
44
33
31
13
Standard letter designations and symbols of radio components and
elements are used on key diagrams. -
To designate each separate element of a key diagram use is made of
figure indexes. For this .purpose each separate unit is assigned a hundred
numbers within which similar components are numbered beginning from 1. The
first two figures designate the unit number, the following figures, ordinal
numbers of the given types of the elements. For example, designations
R7-3, C7-21 given on the diagram should be deciphered as followsg R, C -
letter designations of the diagram elements (resistors and capacitors)
7,- unit number g 3, 219 etc. - ordinal numbers of-the like types of components.
Full designations of the diagram elements, their types, tolerance and
other data are given in the summary Specification (Appendix 4)0
.../Chapter 2
SECRFT
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Chapter2
TRANSMITTING SYSTEM
1. GEN:HAL INFORMATION
The transmitting system of the station le designed for generating
radio-frequency pulses with the power of about 250 kW, of 0.5 microsecond
duration and 1875 c/sec repetition frequency. The frequency range of the
transmitter is from 2700 Mc/sec (11.1 cm) to 2860 Mc/sec (10.5 cm). The
frequency band of the station is obtained by use of four magnetrons of the
following frequency ranges;
MI-18; 2820 to 2860 Mb/sec. (10.638 to-10.489 cm.)
MI-19; 2780 to 2820 Mc/sec. (10.791 to 10.638 cm.)
MI-20; 2740 to 2780 Mc/sec. (10.948 to 10.791 cm.)
MI-21; 2700 to 2740 Mc/sec. (11.111 to 10.948 cm.)
The transmitting system consists of a driver, a modulator, a magnetron
oscillator and a high-voltage rectifier (Fig.13), which are mounted on the
chassis placed in the transmitter cabinet (Figs 14 and 15) located in the
middle of the trailer body.
The modulator oscillator and high-voltage rectifier are housed in one
modulator-oscillator unit.
The driver produces positive square pulses with an amplitude of 2700 V
and of 0.5 microsecond duration to control the modulator.
The modulator is a powerful electronic switch that feeds the magnetron
oscillator with a voltage of about 22 kV for 0.5 Microsecond and cuts it
off for 533 microsecond.
The magnetron oscillator serves to generate A.C. high-frequency pulses
of about 250 kW power.
The high-voltage rectifier is designed to supply the magnetron
oscillator with a voltage (of about 22 kV.)
.../2. FUNCTIONAL
SECRE1
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OE. Lli
?29
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2. FUNCTIONAL DIaGRAT OF TRANSMITTING SYSTEM
Fig.16 shows the transmitting system functional diagram. The negative
trigger pulses of 1.5 microseconds with an amplitude of about 15V and, of
1875 c/sec repetition frequency fed out from the range unit control the
operation of the driver electron relay.
The electron relay produces negative square pulses of 0.9 microseconds
duration with an amplitude of 160 V which are fed to the inverter.
The inverter amplifieS these voltage pulses simultaneously altering
their polarity from negative to positive without changing their duration.
Then they are supplied for further amplification by the first and second
power amplifiers.
From the output of the second power amplifier the negative pulses are
passed through the delay line to the input of the first amplifier valve with
a delay of 0.5 microsecond after it has been triggered by positive pulses
coming from the inverter.
From pulse transformer Tr23-2 changing the polarity of voltage pulses,
positive pulses with an amplitude of 2700 V and of 0.5 microsecond duration
4110 are applied to the modulator valve grids.
Two rectifiers located in the driver supply the grid and plate circuits
of the driver valves, except for the plate circuits of the second power
amplifier which are fed by the rectifier situated in the modulator?oscillator
unit.
Storage capacitor 025-5 placed in the modulator is charged to 22 RV by
the high?voltage rectifier.
In the intervals between the voltage pulses furnished by the driver,
the modulator valves are not conducting as they are cut off by negative
bias, and the storage capacitor cannot discharge through them.
The positive voltage pulses coming from the driver make the modulator
valves conducting for 0.5 microsecond, the storage capacitor discharges
.../through the
SEMET
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ilotiowmcm
?
?
?
- 30
through the modulator valves and faagnetron which generates ultra high-
frequency pulses of about 250 kW power. Upon cessation of the voltage
pulse action, i.e. 'after 0.5 microsecond, the modulator valves are cut off
again by bias voltage and the magnetron stops generating oscillations until
the next positive pulse arrives from the driver.
The ultra high-frequency pulse 250 kW pulse of 0.5 microsecond duration
produced by the magnetron is passed to the antenna through the feeder
coupled to the magnetron.
In parallel with the magnetron are connected damping diodes which
suppress spurious oscillations appearing in +he modulator circuit after the
modulator vales have been cut off.
3. DRIVER
The driver is composed of the following elements q an electron relay,
an inverter, the first and second power amplifier, two pulse transformers,
a delay line and two rectifiers.
A key diagram of the driver is shown in Fig.17 (See Album).
The front panel and general view are given in Figs 18 and 19.
Electron Relay
The electron relay is the driver input stage forming the negative
square voltage pulse whose shape and duration are determined by the parameters
of the electron relay. Within certain limits the form and duration of the
pulses are not dependent upon those of the trigger pulse.
The electron relay (Fig.20) utilizes double triode ?V23-1 (6N85) and
is triggered by the negative pulse with an amplitude of about 15 V coming
from the range unit.
Before supplying the trigger pulse the right-hand triode of valve
V23-1 is out off by a negative bias of about -16 V applied to grid 1 of the
right-hand triode from the voltage divider formed by resistors R23-7 and
R23-8 which is supplied by -230 V bias rectifier. The left-hand triode
of the valve is opened as its grid voltage approximates to zero.
irfThn r7"
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ULAitatn,.6
- 31 -
In this case capacitor 023-2 is charged to the plate voltage value
of the electron relay (to +230 V). The plate current flowing through
the left-hand triode develops voltage drop across resistor R23-5, as a
result the potential ,of the left-hand triode plate 5 is approximately equal
to +120 V.
The negative trigger pulse from the range unit is applied to grid 4 of
the valve left-hand triode through a differentiating circuit composed of
capacitor 023-1 and resistor R23-2 with a time constant of about 0.15
microseconds. The negative pulse cuts off the left-hand triode (Fig.21,a)
which causes voltage to build up across the left-hand triode plate
(Fig.21, bo). This voltage rise is applied through coupling capacitor
C23-3 to grid 1 of the right-hand triode, which results in opening of the
triode (Fig.21, d).
With the left-hand triode cut off, capacitor 023-3 charges through
resistor R23-5 and the grid - cathode section of the right-hand triode.
The time constant of the charging circuit (023-3, R23-5) is rather
large -(approximately 30 microseconds) therefore, with the left-hand triode
cut off for about 0.9 microseconds the right-hand triode of the valve
remains conducting 3 the grid voltage and plate current in it are changed
inconsiderably during this time interval (Fig.21, do). When plate current
appears in the right-hand triode, voltage drop develops across resistor
R23-6.and choke L23-1, which results in reduction of potential at plate 2
by approximately 160 V (Fig.21, f). The voltage reduction is applied
through coupling capacitor C23-2 to the grid of the left-hand triode, as
a result the left-hand triode remains cut off though the trigger pulse is
1
no longer applied.
The voltage reduction on the plate of the right-hand triode causes
capacitor 023-2 to discharge gradually through the right-hand triode and
resistor R23-2. As the capacitor discharges the voltage drop across
resistor R23-2 caused by the capacitor discharge, current decreases
.urinFT .../gradually in
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OLURCE 1
gradually in value and the left-hand triode grid voltage irwreases. At
the moment when the grid voltage slightly exceeds the trigger level, a
small plate current appears in the left-hand triode. The voltage drop
across resistor R23-5 causes the drop in the plate potential of the left-
hand triode. This voltage drop is fed out through capacitor 023-3 to the
grid of the right-hand triode thereby causing a decrease of its plate
current and, consequently, an increase of its plate potential. The increase
of voltage on the plate of the right-hand triode is applied to the grid of
the left-hand triode through coupling capacitor 023-2 and causes further
rise of its plate current.
Thus, at the instant when the left-hand triode grid voltage reaches
the trigger level, the left-hand triode current increases in an avalanche-
like manner and the right-hand triode plate current fully decreases which
means the circuit comes back to the initial position. The electron relay
remains in this state until the next trigger pulse arrives from the range
unit.
The duration of the negative voltage pulse at the plate of the right-
hand triode, i.e. the time for the circuit turn over, is deteihined in the
main by the time constant of the capacitor (023-2) discharge circuit.
The negative square pulse of 0.9 microseconds duration (Fig.211 f)
generated by the electron relay is furnished from the plate of the right-
hand triode V23-1 to the grid of the inverter valve V23-2 through isolating
capacitor 023-4.
The repetition frequency of the electron relay pulse corresponds to
the frequency of the trigger pulses supplied from the range unit and is
1875 c/sec.
The plates of the electron relay are fed from the rectifier +500 V
through damping resistors R23-41, R23-34 and R23-33.
The amplitude value of the negative pulse voltage produced by the
electron relay is approximately equal to 160 V.
SEDIET
.../Placed in
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OLWIL1
-33?
Placed in the plate circuit of the right-hand triode is correcting
choke L23-1 which serves to improve the pulse wave-form.
.Inverter
The inverter is designed to amplify and reVerse polarity of the
negative pulse furnished by the electron relay. A positive pulse is formed
at the inverter output which is required for removing cut-off bias in the
valve of the next stage (first amplifier) which is cut off in the time
interval between the pulses.
The inverter employs Valve V23-2, type 6.1.3S (beam tetrode) used as
a triode. The valve plate circuit is supplied from the +500-volt rectifier.
If there is no negative pulse applied from the electron relay the
valve grid voltage approximates zero and the current flowing through the
valve is about 45 mA, the plate voltage of the valve being in the region
111 of 105 V.
When the. control grid is fed with the negative pulse the inverter valve
is completely cut off and positive voltage, pulse le built up on its plate,
which is impressed on the control grids of the first power amplifier valve
(V23-3) through isolating capacitor 023-5.. During the pulse action the
valve grid voltage becomes positive with the resultant grid current in the
valve.
The. grid current of the first power amplifier valve flows through
resistor R23710 and develops voltage drop across it equal approximately to
135 V, which keeps the voltage on the plate of valve V23-2 below 365 V
during the pulse action.i
Thus the Amplitude of voltage pulses on the plate of valve V23-2 is
clipped by the grid current of the first power amplifier and makes up '
approximately 260 V.
Apart from correcting choke L23-,-2 the plate circuit of valve V23-2
includes,resistor R23-10 which serves to improve the pulse wave-form at the
inverter output.
SECRET
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?
Fig.22 shows voltage and current curves in the inverter circuits. It
should be borne in mind that the curve of the inverter plate current has
the form shown in this figure only in case the second power amplifier is
not functioning. At normal full connection of the driver the voltage
pulse wave-form on the inverter plate is slightly changed by the action
of the negative voltage pulse. This pulse is supplied from the second
rower amplifier output to the input of the first amplifier through the
delay line and to the inverter plate through coupling capacitor 023-5.
1111 First Power Amplifier
The first power amplifier employs valve V232.3, type GI-30, (a beam
dual tetrode) is designed for further amplification of the pulse furnished
by the inverter.
The simplified diagram of the driver power amplifiers is shown in
Fig.23.
When there is no pulse applied, both halves of the first amplifier
valve are cut off by a negative voltage of -230 V applied to the control
grids from the bias rectifier (valve V23-6), '11.en the positive voltage
4111 pulse (Fig.24, a) is applied from the inver'.er to the control grid of valve
V23-3 the valve of the first power amplifier is made conducting.
The plate load of the first power amplifier is the primary winding of
pulse transformer Tr23-1. The secondary winding of the transformer is the
load of the grid circuit of the second power amplifier.
The plate current flowing in the first power amplifier valve (Fig.24, b)
develops voltage drop across its load, resulting in voltage pulse of
negative polarity on the valve plate whose wave-form approaches the square-
wave (Fig.24, c).
The secondary winding of pulse transformer Tr23-1 is connected into
the grid circuit of the second power amplifier valve so that the positive
voltage pulse produced in this winding is applied to the valve grids of the
next stage.
.M.RFT .../The main
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1
-35-
?
The main function of pulse transformer Tr23-1 is to convert the
negative pulse into a positive one. Nevertheless, the transformer matehes
the output resistance of the first power amplifier with the input resistance
of the second power amplifier.
The transformation ratio of transformer Tr23-1 is 2.5:1 and relationship
of pulse voltages across the primary and secondary windings is 790320 Vg
respectively.
The application of such a step-down transformer is necessitated by
keeping, during the pulse action, a considerable grid current (about 2 A)
consumed by the grid circuits of the second power amplifier.
Reduction of the pulse duration to 0.5 microsecond in the first
amplifier circuits can be explained by the action of the second power
amplifier and the delay line.
The plate and screen circuits of valve V23-3 are supplied by the +850 V.
rectifier located in the driver unit. To prevent appearance of spurious
oscillations the screen circuits include grid suppressors R23-13 and
R23-14, 51 ohms each, whereas the plate circuits - resistors R23-15 and
R23-169 10 ohms each (Fig.17).
Second Power Amplifier
The second power amplifier is designed for further amplification of
voltage and power of the pulse furnished by the first amplifier.
The amplifier employs two valves V23-4 and V23-59 type GI-30, connected
in parallel. Thus, the second power amplifier uses a parallel combination
of four tetrodes.
Resistor R23-28 serves to clip the current flowing directly from the
rectifier when valves V23-3 and V23-4 are conducting.
? In pulse intervals the valves of the second power amplifier are cut off
by a negative voltage of -230 V fed to the control grids from, the bias
rectifier (valve V23-6).
SECRET
.../The valve
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%7KtigiL
- 36 -
The valve plates are supplied with D.C. voltage from the +4000-volt
1110 rectifier accommodated in the modulator-oscillator unit.
With the positive voltage pulse impressed on the control grids of the
amplifier valves a large pulse current flows thrOugh the valves. This
current is maintained due to discharge of capacitor 023-8 which is charged
during the pulse intervals up to the plate voltage of the second power
amplifier.
Connected into the discharge circuit of capacitor 023-8 is the primary
winding of transformer Tr23-2. The winding is the plate load of the second
power amplifier valves. Thus, the second power amplifier is a transformer-
coupled amplifier based on a circuit with a parallel Supply.
If transformer Tr23-2 were connected similarly to transformer Tr23-1
(Fig.25), large D.C. potential difference would occur between the windings
of transformer Tr23-2, amounting to about 5400 V (+4000 across the primary
and -1400 across the secondary).
This would demand strengthening of the insulation between windings,
which would result in an increase of the transformer leakage inductance and,
? therefore, in a slight impairment of the pulse wave-form.
When the pulse of the plate current passes through the primary winding
of transformer Tr23-2, the primary winding creates the negative pulse
having an amplitude of about 3200 V.
The main function of transformer Tr23-2 is to reverse the pulse
polarity.
The relationship between the number of turns in the transformer
windings is 1;1, but due to losses in the transformer the voltage in the
secondary winding decreases approximately to 2700 V.
The positive pulse furnished from the tranSformer secondary winding
is applied to the grids of the modulator valves.
Connected in parallel with the primary winding of transformer Tr23-2
is a chain composed of capacitor 023-9 and resistors R23-31 and R23-30,
rffirettnw-Te .../which improves
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afrigHL
-37-..
?
?
?
which improves the wave-form of the pulse applied to the gride of the
modulator valves.
Leakage inductance of the primary winding of transformer Tr23-2 and
distributed capacitance of this winding, including the wiring capacitance,
form an oscillatory circuit in which spurious oscillations are shock
excited at the moment of the beginning and cessation of the plate pulse
current of the second power amplifier valves. The correcting chain shunts
this oscillatory circuit, reduces its quality and ensures quick damping of
the spurious oscillations, thus improving the wave-form of the voltage pulse
?at the output of transformer Tr23-2.
Delay Line
To reduce the duration of the voltage pulse produced by the electron
relay from 0.9 microsecond to 0.5 microsecond use is made of a delay line
made in the form of an artificial line. The delay line is connected
between the output of the second power amplifier and the input of the first
power amplifier (Fig.23).
The delay line acts as follows. The voltage divider formed by
resistors R23-29 and R23-40 furnishes part Jf the pulse voltage of negative
polarity to the line input. A series combination of four sections of
inductor L23-3 and. a parallel combination of capacitors 023-10 and 023-22,
023-11 and 023-23, C23-12 and 023-24, 023-13 and 023-25 prevent instantaneous
transmission of voltage along the line. As a result the voltage pulse at
the line output appears and vanishes a bit later than at the line input.
The line parameters are selected so that the pulse delay time equals
0.5 microsecond.
To avoid reflection from the line end, the line is loaded by resistor
R23-39 whose value approximates the line wave impedance.
The pulse of 0.9 microseconds duration generated by the electron relay
is narrowed on the grid of the first power amplifier (valve V23-3). The
SECRET'
.../grid of
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scruT
grid of this valve is supplied with the positive voltage pulse from the
inverter and the negative pulse delayed for 0.5 microsecond from the second
amplifier through the delay line.
The amplitude of the negative voltage pulse exceeds that of the positive
pulse, therefore, the first amplifier is cut off by the negative pulse from
the delay line 0.5 Microsecond after it has been made conducting by the
pulse furnished from the inverter. Thus, the valve is conducting during
0.5 microsecond, hence the voltage pulse duration at the anode (plate) of
the first power amplifier and in the successive stages is 0.5 microsecond.
Fig.26 shows the voltage curves in various points of the power rectifier
circuit (by a line of dashes - when the delay line is absent and by a
continuous line - Curves actually observed when the delay line is present).
The pulse from the delay line output is applied to the control grid of
the first power amplifier through capacitor 023-19 isolating the valve grid
from the chassis for D.C. The capacitance value of thip capacitor is taken
small (47 pF) to diminish its influence upon the inverter pulse form as the
capacitor shunts the plate load of valve V23-2 for A.C.
Tulse Transformers
Transformers Tr23-1 and Tr23-2 are transformers of a special type
intended for undistorted transmission of short pulses. To perform this
operation it is necessary to ensure minimum leakage inductance in the
transformer and minimum capacitance between the windings. Reduction of
leakage inductance is obtained by the close arrangement of the transformer
windings, whereas reduction of interwinding capacitance is achieved by
placing them as far apart as possible.
The problem is solved by arranging the windings in a special manner.
Leakage inductance is minimum if both windings have the same volume.
Therefore, each winding of transformer Tr23-1, having transformation ratio
2.50 consists of two sections, the primary sections being Connected in
series, and the secondary sections - in parallel (Fig.27).
(Timm inaCIA AA
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Ntall
- 39 ?
Used as a core material ib permalloy - an Aloy of iron and nickel -
having high magnetic permeability.
To reduce eddy current loss, silicon is added to the alloy, the
laMinations are made 0.1 --0.12 mm thick and ard thoroughly insulated from
each other by a film bf varnish applied to one bide of each lamination.
The core of transformer Tr23-2 is greater in volume than that Of
transformer Tr231 as the power transmitted by the transformer Tr23-2 reaches
50 - 55 kW during the pulse time.
Driver Rectifiers
The driver unit is prcivided with a plate rectifier and a bias rectifier.
The bias rectifier (Fig.28) uses valve V23-6 (kenotron, type 504S) in
a full-wave circuit. It produces bias voltage (-230 V) to supply the first
and second power rectifier valves. The bias voltage applied to the electron
111 relay (-16 V) is taken off the voltage divider which is also fed by the
same rectifier. Besides, the rectifier supplies an electron time relay
incorporated in the modulator unit. In some stations the -230 V rectifier
supplies relay P23-1 through series resistor R23-32.
Note The electron time relay and relay P23-1 are described
below in Section 7.
The bias rectifier filter consists of capacitor V23-14 and choke DL23-1.
The primary winding circuit of transformer Tr23-3 includes fuse B23-1
located on the front panel of the unit.
The plate rectifier of the driver unit (Fig.29) utilizing two valves
V23-7 and V23-8 (kenotrons, type 5045) and transformer Tr23-4, is represented
by two independent rectifiers for +500 V, and +350 V, connected in series.
The rectifier rated for +500 V supplies the plate circuit of the inverter
and electron relay. The mid-point of the transformer plate winding
(i.e. minue) of the +350 V rectifier is connected to the output (plus) of
the rectifier, +500 V. Thus, the total voltage of the driver second
.../rectifier equals
trrrtrr
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AM
- -
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%sr amy ti46,
?
?
rectifier equals +850 V. The voltage of +850 V is used for supplying the
plates of the first power amplifier and the screen grids of the first and
second power amplifiers.
The primary winding circuit of transformer Tr23-4 includes fuse B23-2,
located on the front panel of the unit.
The filament voltage of the driver valves is taken from transformer
Tr23-5 (Fig.17) which is provided for this purpose with four secondary
windings a winding with taps 9 and 10 for heating valves V23-1, V23-2
V23-3 V23-4 and V23-5 of the driver unit; a winding with taps 5 and 6 for
kenotron V23-7 and a winding with taps 7 and 8 for kenotron V23-8 of the
double rectifier. The fourth winding with taps 3 and 4 is not used in the
driver unit.
The mains voltage is applied to the driver unit through connector
Zw23-1, whose contacts 15 and 16 supply 110 V, 427 c.p.s. to transformers
Tr23-3 and Tr23-5, whereas contacts 11 and 12 - to transformer Tr23-4.
Connector Zw23-1 is simultaneously used for feeding the driver rectifier
voltages to an indicator, type Pp25-3, (marked VOLTAGE CHECK) located on
the front panel of the transmitter unit, and to the electron time relay
placed in the modulator unit.
The indicator, type Pp25-3, is supplied through contact 5 and series
resistor R23-38 with a voltage of -230 V; through series resistor R23-36 and
contact 9 of connector Zw23-1 with a voltage of +500 V and through resistor
R23-37 and contact 7 with a voltage of +850 V. All these voltages are fed
to the instrument through selector switch W25-4.
The instrument connections are made in such a way that when voltages
of -230, +500 and +850 V are checked the instrument pointer must be between
the red marks made on its scale.
Voltage to the electron time relay is applied through contact 13 of
connector Zw23-1. In drivers of stations of earlier design the contact
circuit of relay P23-1 is closed through contacts 13 and 14 of connector
Zw23 -1.
SECRET
.../The plate
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- 41 -
The plate voltage of +4000 V is applied to the second power amplifier
from the rectifiers +4000 V, located in the modulator-oscillator unit,
through high-voltage connector Zw23-2. The pulse voltage is impressed on
the grids of the modulator valves from transformer Tr23-2 through high-
voltage connectors Zw23-6 and Zw23-7.
MODULATOR.
The modulator is a powerful electronic switch periodically energizing
the magnetron plate circuit. The basic elements of the modulator are formed
by three valves V25-1, V25-2 and V25-3 (type GMI-30) connected in parallel,
storage capacitor C25-5, three damping diodes V25-4, V25-5 and V25-6
(W1-0.1/40) and charging choke L25-2.
Key diagrams of the modulator-oscillator unit are shown in Figs 30
and 30,a (See Album).
The grids of the modulator valves are furnished with the constant
negative bias of -1400 V from the bias rectifier employing valve V25-8
(VU-111-D). During pulse intervals the modulator valves are cut off. The
plates of the modulator valves are connected to storage capacitor C25-5
(Fig.31).
In time intervals between the positive pulses fed to the grids of the
modulator valves, the storage capacitor is charged by the high-voltage
rectifier to a voltage of about 22 kV. The capacitor is charged along the
following circuit (Fig.31): plus of the high-voltage rectifiers current-
limiting resistors R25-36, R25-35, capacitor C25-5, choke L25-2, milli-
ammeter 425-2, minus of the rectifier (ground).
When the positive pulse is received from the driver to the grids of
the modulator valve (Fig.32, a), the valves become conducting and the
magnetron is connected into the charging circuit of storage capacitor
025-5, in series with the modulator valves. In this case voltage drop
across the modulator valves will be comparatively small (approximately
1 - 1.5 kV) and air rt entire voltage of the storage capacitor is applied
isOrnnrir /.
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tYlviAL
- 42 -
?
?
in negative polarity to the magnetron cathode, as the anode is earthed
(Fig.329 c$ d). The magnetron generates oscillations of ultra-high frequency.
Due to relatively large capacitance of storage capacitor C25-5
(O.125.microF)and short discharge time (0.5 microsecond), the voltage across
the capacitor during the discharge time decreases by a value not exceeding
200 V (Fig.32, b). Thus, the voltage impressed on the magnetron remains
practically constant during the pulse time.
The conducting modulator valves pass besides discharge current of
capacitor C25-59 the current supplied directly by the high-voltage rectifier.
For limiting the value of the rectifier current flowing through conducting
modulator valves, current-limiting resistors R25-35 and R25-36 are included
in the circuit.
The value of these resistors is such that during the resting time storage
capacitor C25-5 may practically be charged up to full rectifier voltage.
In time intervals between the pulses charging current of capacitor
C25-5 flows through milliammeter L25-2. During the pulse time capacitor
C25-5 discharges through the magnetron. In this case the instrument reads
the magnetron average current as the electricity stored by the capacitor
during the pulse intervals equals the electricity lost by the capacitor
during the pulse time.
The average value of the magnetron current at normal operating
conditions of the magnetron amounts to 21 - 23 mA.
Knowing average magnetron current Iavg pulse duration T and pulse
repetition rate T it is possible to determine the magnetron pulse current.
According to equation I
pulse= I
aV T . In this case: T = 0.5 microsecond
1
T = 1875 sec. =
533 microseconds. Hence the magnetron current during the pulse will be;
1.
ulse = 'av. 533 ? x - 22 x 10-3 x 1066 = 23.5 Amp.
p 0.5
To provide the proper pulse wave-form of high-frequency oscillations
produced by the magnetron, the wave-form of the pulse produced by the
SFP,1111
?"modulator must
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nrir
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?
?
?43?
modulator must approach the square wave-form. For this purpose a number
of correcting elements is placed in the modulator circuit.
To increase the steepness of the pulse trailing edge the grid circuit
of the modulator valves includes choke L25-1 (2.5 mH) and in parallel with
the magnetron - choke L25-2 (5 mH). Choke L25-2 serves to increase the
steepness of the voltage pulse trailing edge on the magnetron cathode. The
ahoke ensures more rapid discharge of the capacitance existing between the
magnetron cathode circuits and earth (capacitor Op see Fig.31) after the
modulator valves have been cut off. By' the time the modulator valves are
cut off, the current in the choke amounts to rather a large value (of the
order of 2.2 A). With the valves cut off this current ensures rapid
discharge of the stray capacitance between the magnetron cathode and earth,
its value is not diminishing with time but, on the contrary, increases
until the voltage between the magnetron cathode and earth falls practically
to zero.
After that the current in the choke begins decreasing whereas the
voltage on the magnetron cathode starts increasing, being positive in
relation to earth.
Thus, damped oscillations should develop in the circuit formed by
choke L25-2 and the stray capacitances magnetron cathode - earth (Op).
During negative half-periods of this damped A.0 voltage high-frequency
oscillations might be regenerated on the magnetron cathode. To damp
spurious oscillations in the circuit and thereby prevent regeneration of
high-frequency oscillations damping diodes V25-4, V25-5 and V25-6 (kenotrons,
type B-0.1/40) are connected in parallel with the magnetron. During the
positive half-wave the diodes shunt the oscillatory circuit and the spurious
oscillations are auenched. Fig33 shows voltage pulse wave-forms on the
magnetron cathode for three versions of the circuits with inductance (L25-2)
without diodes, with diodes without inductance, and with diodes and
inductance.
SECR
.../Choke L25-1
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?44?
Choke L25-1 increases the steepness of the pulse trailing edge on the
grids of the modulator valves, thus ensuring a most rapid discharge of the
capacitance existing. between the modulator valve grids and earth.
To check the wave-forms of voltage pulses on the grids of the modulator
valves and on the magnetron cathode the right-hand part of the transmitter
cabinet front panel is provided with test connectors Zw25-3 and Zw25-4.
Voltages are applied to these connectors from capacitive voltage dividers
formed by capacitors 025-3 - 025-2 and 025-7, and capacitance between the
screw fastening the insulator of storage capacitor C25-5 and capacitor
025-5 itself. The screw is isolated from the chassis.
Test connectors Zw25-3 and Zw25-4 are connected with the capacitive
voltage dividers through resistors R25-34a - R25-34b and R25-33, which serve
to suppress spurious oscillations occurring in the pilot circuits.
The grid and plate circuits of the modulator valves include grid.
111 suppressors in grid circuits they are as follows R25-43, R25-44, R25-45
(10 ohms each) in plate circuits R25-40, R25-41, R25-42 (10 ohms each).
The grid suppressors serve to damp spurious oscillations appearing sometimes
in the circuit consisting of distributed stray inductances and capacitances,
as well as to equalize load currents in the grid and plate circuits of all
three triodes.
?
5. MAGNETRON OSCILLATOR
The magnetron oscillator serves to produce strong high-frequency
pulses. Frequency of the generated oscillations is within the range of
from 2700 to 2860 Mc/sec, the pulse power is 250 kW, and the pulse duration
is 0.5 microsecond. It consists of a special oscillation valve magnetron
and a permanent magnet between the poles of which the Magnetron is placed.
411 The magnetron generates high-frequency oscillations when it is
supplied with plate voltage coming from the modulator.
The high-frequency energy is passed from the magnetron to the station
antenna through the feeder line.
(tonna
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?
?
?
?
-45-
etron
The, transmitter unit of the radar station employs a multi-cavity
magnetron, 'type MI-18 (MI-19, MI-20, MI-21).
The magnetron (Fig.34) consists of the following main components an
anode block, a cathode, a high-frequency lead, heater leads and a finned
body.
The anode block of the magnetron is a metal cylinder in which eight
cavities are cut connected with the central one by slots. The inner surface
of the anode block consists of a combination of slots and segments.
At ultra-high frequencies current flows not through the metal body of
the entire anode block of the magnetron, but only through a thin surface
layer. Thus, it appears as if the block cavities were made up of a thin
conducting film of metal and the remaining volume of metal is an ideal
dielectric for ultra-high frequencies.
Each cavity together with a slot is a resonance circuit which is
coupled to the central cavity and the remaining circuits.
An output coupling loop is inserted into one of the anode circuits to
transmit the ultra-high frequency energy from the magnetron to the feeder.
Due to close coupling between the resonance circuits the energy of all
the block circuits is passed to the feeder through the, high-frequency lead.
The central cavity incorporates a powerful oxide-coated cathode serving
as an electron emitter. The heater leads of the magnetron are insulated
from the body and are protected against damage by a glass cup.
To make cooling of the magnetron more effective the outer circumference
of the anode block is fitted with radiating fins which stand in the way of
the air flow forced by the fan.
Thus the magnetron is a cylindrical two-electrode valve with a special
anode. When the magnetron is functioning it is placed in permanent
magnetic field directed along the cathode axis.
SECRET
.../The nature
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AMMI
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Ito=ung.,
- 46 -
?
?
The nature of physical process, occurring in the magnetron when high-
frequency oscillations are generated, can be approximately presented as
follows:
Each electron moving in space between the magnetron anode and cathode
is acted on by three fields g permanent Magnetic field H (directed along the
cathode axis); permanent radial electric field E, (directed fron the anode
to the cathode); a high-frequency electric field (set up between the anode-
block segments).
The influence of electric fie]d E upon the negative charge is
characterized by the force proportional to the electric field intensity
FE = e.E.
The influence of the magnetic field upon the moving charge is
characterized by the force proportional to the intensity of magnetic field
H and charge velocity v:
FHK.v.H.
where K is proportionality coefficient.
The direction of force FE acting on the negative charge in the electric
field is opposite to the direction of intensity of field E. Force FH acts
on the moving charge in the direction perpendicular to velocity vector v
and the magnetic intensity vector 119 and therefore, changes only the direction
of the charge travel, the absolute velocity value being unchanged.
The trajectories of electrons in the two-electrode cylindrical magnetron
are shown in Fig. 35.
When there is no magnetic field the electron travels along the straight
line (trajectory A); with the magnetic field intensity less than certain
value Hk, the electron trajectory differs from the straight line (trajectory
B); with the magnetic field intensity exceeding value Hk called critical
field intensity, the trajectory is curved so that the electron without
reaching the anode comes back to the cathode (trajectory C).
SUET
.../A more
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Aft M. Oa M V2111
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? 47 ?
A more detailed analysis of the motion of electrons in electric and
magnetic fields arranged at right angles (when the Magnetic field intensity
_exceeds the critical intensity) shows that the electron trajectory is a
cycloidal path, i.e. resembles the trajectory of a point on the rim of a
wheel rolling over the surface without sliding (Fig.36).
As the electron moves away from the cathode its velocity increases and
when it reaches the cathode its velocity dedreases and at the cathode surface
the velocity equals zero.
Thus, the motion of electrons in a magnetron with a planar cathode may
be considered as a sum of two motions, uniformly-translational motion in
the direction parallel to the anode surface, and rotary motion.
The velocity of translational movement of the electron, i.e. the average
velocity of the electron in the direction parallel to the anode surface, is
proportional to
To explain explain the process of maintaining sustained oscillations in the
magnetron let us assume, as it is usually done when analysing the operaticn
of self-excited generators, that at the initial moment there are high-
frequency oscillations caused in the cavities by an external cause (sharp
change of voltage, etc.). These oscillations whose frequency is determined
by the cavity dimensions develop at the slots of the cavities, i.e. between
adjacent anode segments, an alternating electric field.
The oscillatory circuits (cavities) are coupled to each other by the
segments of the anode central cavity. Therefore oscillations in any pair
of neighbouring circuits are shifted in phase by one half-period (Fig.37).
By selecting the magnitude of relation -R-, it is possible to set such a
velocity of the translational movement of electrons which are in the space
between the cathode and anode, that the time required for the electron to
cover the distance equal to that between the anode slots, will amount to one
half-period of resonant oscillations in the anode circuits. When the
.../mentioned condition ?
SECRET
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mentioned condition is observed the electron, that left the cathode and
passed by the first encountered anode slot at the instant when the maximum
retardation field of high-frequency oscillations acts about the slot, will
approach the next anode slot just at the momeht the maximum retardation
field also acts near it.
When the electron moves at the first slot in the retardation field its
velocity is slightly decreased. This means that part of the electron
kinetic energy is spent to increase the energy stored in the circuit,
i.e. to increase the energy of radio-frequency oscillations. Due to a
decrease in the kinetic energy the electron while travelling further along
its trajectory- completely loses its velocity, i.e. stops at some distance
from the cathode without reaching its surface. Then by the action of the
positive voltage applied to the magnetron anode the electron starts moving
towards the anode again describing a second path of its cycloidal trajectory.
When passing near the second slot of the anode in the radio-frequency
retardation field the electron gives up part of its kinetic energy this time
to the second anode circuit. As a -result the next path of the cycloidal
trajectory of the electron begins at the point located at greater distance
from the cathode, etc.
Thus passing near the anode slots and each time giving part of the
energy gained due to the anode voltage supply to the anode circuit the
electron gradually moves away from the cathode and ultimately reaches the
anode (Fig.37).
It is obvious that the electron energy given up to the oscillatory
circuits favours maintenance of sustained oscillations in them. Therefore,
the electrons like those considered above may be called the electrons moving
in a favourable phase.
Besides these electrons, the cathode emits electrons that start moving
in an unfavourable phase. Passing near the first encountered slot this
.../electron gains
ST-111[T
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OLLHULI
? 49 ?
electron gains additional acceleration, as a result it arrives a+ the
cathode surface with appreciable velocity and is absorbed by the cathode.
Therefore, the electrons leaving the cathode surface in the unfavourable
phase gain acceleration in the radio-frequency field once. The electron
transit time in the space between the cathode and the anode is much shorter
than that of the electron that left the cathode in the favourable phase.
Thus, the so-called "sorting" process takes place in the magnetron as
a result of which at any moment the inter-electrode space of the magnetron
contains much more electrons moving in the favourable phase than those
moving in the unfavourable phase.
A more d,Aailed analysis shows that the radio-frequency field component
perpendicvlar to the anode surface also furthers bunching of electrons into
clouds around those moving in the most favourable phase.
Thus the density of electrons moving in the space charge is not uniform.
The space charge regions with the most heavy density of electrons take the
form of a spoked wheel which rotates about the cathode (Fig.38). The
space charge spokes rotate in synchronism with oscillations of the anode
? block electromagnetic field. Each spoke of the space charge passing the
anode slots encounters maximum retardation radio-frequency field and gives
up part of the energy of its electrons to the oscillatory circuits thus
maintaining sustained oscillations in the circuits.
The magnetron, type MI-18 (MI-19, MI-20, MI-21), employed in station
SON-9 operates under pulsed conditions. The magnetron anode is earthed.
The cathode is fed with negative voltage pulses. The frequency of the
magnetron generated oscillations is determined in the main by dimensions of
the cavities but in narrow limits it may be varied depending upon the
magnetron mode of operation.
For optimum mode of operation the magnetron cathode should be furnished
with pulses of 20 - 22 kV, whereas the magnetic-field intensity should
amount to 1900 oersteds. In these Conditions the pulse current through
SFET
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the magnetron is 23.5 A.
110 When the ratio of the period of pulse repetition to the duration of
?
?
?
the pulse (T) is 10669 then the average value of the current through the
magnetron is 22mA.
Permanent Magnets
TO create a magnetic field required for the magnetron operationuse
is made of permanent magnets fabricated from magnico alloy.
The magnets are comp,7ised of two horn-like poles 2 (Fig.39) between
which magnetron 4 is placed. Both poles are secured., on steel plate 5
having low magnetic resistance.
The poles are placed opposite to each other and the gap between them
can be varied with the help of a worm gear when rotating knob 1 situated on
the magnet plate.
The plate with the magnets is attached to base 9 which in its turn is
secured to the antenna pedestal foundation. Fixed to the same base by
three thumb-screws is plate 6 which mounts the magnetron. The magnetron
is located in the gap between the poles in such a way that the lines of
force of the magneticfield built up by the magnets are in parallel with the
magnetron cathode.
The average value of the magnetic field intensity must make up
1900 oersteds, but the value may vary for various magnetrons.
The required value of the magnetic field intensity is provided during
tuning by rotating the gap control knob according to instruments Pp25-2
(MAGNETRON CURRENT) and Pp25-1 (NIGH VOLTAGE) situated on the front panel
of the modulator-oscillator unit.
6. RECTIFIERS
The modulator-oscillator unit accommodates three rectifiers as followsg
a rectifier +4000 V, a rectifier -1400 V.and a high-voltage rectifier for
22 kV.
.../The rectifier,
'
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uuumw..
- 51 -
?
The rectifier, +4000 V, is a plate voltage supply of the driver second
power amplifier valves. The rectifier is based on a full-wave circuit
using valves V25-9 and V25-10 (kenotrons, type VU-111-D).
The rectifier circuit includes plate transformer Tr25-4, heater
transformer Tr25-5 (Fig.40) and filter capacitor C25-8. To protect the
rectifier from overloads, overload relay R25-4 is placed in its 'negative
circuit. This circuit also includes undervoltage relay P25-8 which will
be dealt with in section 7 of the present Chapter.
The value of the rectifier voltage is checked by instrument Pp25-3
marked VOLTAGE CHEGE (with switch W25-4 in position +4000) located on the
front panel of the modulator-oscillator unit.
When the rectifier voltage is normal the pointer of instrument Pp25-3
should come to set between two red marks on the instrument scale.
Placed in the circuit of instrument Pp25-3 are series resistors
R25-48 - R25-53 and potentiometer R25-30, which serves to set the instrument
pointer in the middle between the red marks at the rectifier rated voltage
of +4000 V.
The rectifier, -1400 V, produces negative bias voltage applied to the
grids of the modulator valves. The bias rectifier is based on a half-wave
circuit using valve V25-8, type VU-111-D (Fig.41).
The rectifier circuit includes plate transformer Tr25-9 and heater
transformer Tr25-10. Capacitors 025-1 and 025-6 are used as a filter.
From the mid-point of the divider formed by resistors R25-37 and
R25-38, the voltage of -820 V is applied through resistor R25-39 and connector
Zw25-8 to the keep-alive electrode of the antenna change-over switch T.R. cell.
Connected in series with resistors R25-37. and R25-38 is the coil winding
of undervoltage relay P25-1, which operates to close its contacts in the
interlocking circuit of magnetic starter P25-1 only after. the voltage at the
bias rectifier output has reached a value of about -1400 V (See Section 7
of the present Chapter).
SECR
.../The rectifier
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%3LUALm
- 52 -
The rectifier voltage value is checked by instrument Pp25-3 (VOLTAGE
CHECK) with switch W25-4 placed in position -1400.
When the rectifier voltage is normal the pointer of instrument Pp25-3
should come to set between the two red marks.
Placed in the circuit of the instrument are resistors R25-46, R25-58
and potentiometer R25-29 which serves to set the instrument pointer between
the red marks.
The high-voltage rectifier, 22 kV, is used to place charge on storage
capacitor 025-5 which stores the energy to supply the magnetron oscillator.
The high-voltage rectifier employs a voltage doubling circuit (Fig.42)
and contains the elements as follows:
a transformer unit (high-voltage plate transformer Tr25-6 and heater
transformer Tr25-8) with two kenotrons, type W1-0.1/40 (V25-11, V25-12);
capacitors 625-9 and 025-03
potential regulator Tr25-7 (in stations of earlier design an. auto-
transformer or a voltage regulator is used) for continuous variation of
voltage across the primary winding of high-voltage transformer Tr25-6.
The potential regulator is provided with one primary and one secondary.
winding. The primary winding is arranged on the rotor of the potential
regulator and the secondary winding - on the stator. The rotor can turn
with regard to the stator, which results in changing the coupling of the
? stator and rotor windings. This in turn causes the change in voltage taken
from the secondary winding of the potential regulator.
The value of voltage applied to the primary winding of high-voltage
transformer Tr25-6 and consequently the value of the rectifier output voltage
is adjusted by means of potential regulator Tr25-7 whose control knob
DECREASE - INCREASE is situated on the front panel of the modulator-
oscillator unit.
The rectified voltage is taken off capacitors 025-9 and 025-10. The
negative pole of the rectifier is earthed through relay P25-5 which protects
from nvnrloads. orrinirr
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39..UBt11.1
- 53 -
The rectifier voltage doubling circuit consists of a series combination
of two half-wave rectifiers, both rectifiers using one secondary winding of
the plate transformer.
One of the half-wave rectifiers is based on the secondary winding of
transformer Tr25-6, valve V25-11 and capacitor 025-9. The positive
terminal of this rectifier is in point a, the negative terminal is in point
Ts. The second rectifier is based on the same secondary winding of
transformerTr25-6, valve V25-12 and capacitor 025-10. The positive
terminal of the second rectifier is in point b, while the negative one in
point c.
Thus, the total voltage of both rectifiers, i.e. double voltage, is
obtained between point S a and b. this cii-cuit functions as follows:
Suppose, that at a certain instant the voltage polarity across the
secondary winding of transformer Tr25-6 is such, that the plate of valve
111 V25-11 is fed with the positive voltage. By the action of this voltage,
the current flowing through valve V25-11 charges capacitor 025-9 to a
voltage approximating the voltage of the secondary winding of transformer
411 Tr25-6. During the next half-cycle, when the negative voltage is applied,
capacitor C25-10 charges through valve V25-12. This capacitor will charge
to a voltage approximating to that of the secondary winding of transformer
Tr25-6. During the period when neither of the capacitors charges both
of them connected in series are discharging to the load which is under
-double voltFge as compared with the voltage across the secondary winding
of transformer Tr25-6.
The high-voltage rectifier voltage is checked by instrument Pp25-1
(HIGH VOLTAGE) connected in series with a chain of series resistors R25-1 -
R25-25 making up approximately 15 megohms in all. The chain of series
411 resistors is supplied with a half of the rectified voltage taken off
capacitor 025-10. The scale of instrument Pp25-1 is graduated to measure
full voltage of the high-voltage rectifier.
grin .../To protect
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?
?
To protect the operating personnel against possible shocks by high
voltage provision is made in the transmitting system for door interlocks
W25-5 - W25-10, isolating the high-voltage rectifiers when the interlocking
circuit is disconnected.
To protect the transmitting system elements against excess currents
provision is made for a definite sequence of connection of separate elements,
their maximum protection and emergency switching.
7. CONTROL, INTERLOCKING
AND SIGNALLING CIRCUITS OPERATION
Operation of the Control Interlocking and signalling circuits.
The control, interlocking and signalling circuit of the transmitting
system are shown in key diagrams of the driver and modulator-oscillator as
well as on diagrams of control5 interlocking and signalling circuits
presented in Figs 43 and 43a (See Album). In Fig.43 a (see Album) are shown
the control, interlocking and signalling circuits of the sets of earlier
design.
From contact block P:03-1 of the control panel the mains voltage of
220V, 50 c.p.s, is applied to block P125-2 of the transmitting system. The
mains voltage of 110 V, 427 c.p.s. is fed to contact block P125-1 from blocks
P113-5 and P113-6.
With switch W25-1 disconnected all the circuits of the transmitting
system are de-energized. When the switch is on the mains voltage of
220 V, 50 c.p.s. is applied through its contacts 5-6, 7-8 and 9-10 to
transformers Tr25-1 and Tr25-2 for heating the modulator valves and damping
diodes, to dial lighting lamps Z25-201 Z25-21 and Z25-22, electric motor
M25-1 of the fan cooling the magnetron and modulator valves as well as to
connector Zw25-10 for supplying the cooling fan motor in the transmitter
cabinet.
Simultaneously, the mains voltage of 110 V, 427 c.p.s. is applied
through contact 1-2 and 3-4 of switch W25-1 to transformers Tr25-10
CCPUT .../and Tr25-:5
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and Tr25-5 for heating the kenotron of the -1400 V rectifier and valves
? of the +4000 V rectifier to transformers Tr25-8 and Tr25-3 for heating the
?
?
?
high-voltage rectifier valves and magnetron respectively, to transformer
Tr25-11 for heating the electron time relay valve, to pilot lamp N25-13
(MAGNETRON HEATING) and through contacts 15 and 16 of connector Zw25-1 to
transformers Tr23-5 and Tr23-3 for heating the driver valves and -230 V
rectifier, respectively.
The bias rectifier voltage (-230 V) is applied to valve V25-23 of the
electron time relay. In 45 seconds, the plate current of valve V25-23
causes individual point relay P25-6 to close its working contacts.
Thus, with switch W25-1 on, voltage is applied to heater transformers
of all valves of the transmitting system, to the fan motors, the bias rectifier
transformer, and the electron time relay.
In stations of earlier design use is made of electromechanical relay
P25-6 which is fed by 220 V, 50 cop 8. A.C. Mains.
The electron and electromechanical time relays are described below.
When the time relay operates, white pilot lamp N25-14 (TIME RELAY) comes
on indicating that voltage may be applied to the modulator valve bias
rectifier and to transformer Tr23-4 in the driver unit. These voltages are
switched on by button W25-2 ON, BIAS, SCREEN.
Pressing button W25-2 closes the supply circuit of magnetic starter
P25-1, but the latter operates only in case the contacts of door interlocks
W25-5, W25-6, W25-7, W25-8, W25-9, W25-10 are closed (in stations of earlier
design including the contacts of relay P23-1 located in the driver unit).
When magnetic starter P25-1 operates, green pilot lamp N25-15 (BIAS and
SCREEN) comes on, the mains voltage of 110 VI 427 c.p.s. is applied to plate
transformer Tr25-9 of the bias rectifier -1400 V and through contacts 11 and
12 of connector Zw25-1 to transformer Tr23-4 accommodated in the driver unit;
the mains voltage of 220'V, 50 c.p.s. is applied to the electromagnet coil
?"winding of
SEA
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winding of relay P25-7 which operates to open the discharge oircuit of
capacitors 025-9, 025-10 and 025-5.
When the modulator valve bias rectifier, -1400 Vg is on, its output
voltage causes relay P25-3 to operate. The relay contacts close the
interlocking circuit of magnetic starter P25-1. After the starter and the
relay have operated, button W25-2 ON BIAS AND SCREEN may be released, since
the coil winding of the
interlocks "A" and "B",
(as well as contacts of
starter electromagnet is
closed through the starter
normally closed contacts of overload relay P25-4
overload relay P25-9 in stations of earlier design),
contacts of relay P25-3 and button. W25-2.
Pressing any of buttons W25-3 (ON, HIGH VOLTAGE) located on the front
panel of the modulator-oscillator unit or button W4-5 situated on the front
panel of the range mechanism unit, closes the supply circuit of the
electromagnet coil winding of starter P25-2 and causes the latter to operate.
When the magnetic starter operates red pilot lamp N25-16 (HIGH VOLTAGE)_
comes on and the mains voltage 110 Vg 427 c.p.s. is applied to transformer
Tr25-4 of the
the latter to
When the
rectifier (+4000 V), potential
high-voltage plate transformer
rectifier (+4000 V) is on, its
regulator Tr25-7 and through
Tr25-6.
load current causes undervoltage
relay P25-8 to close the interlocking circuit of magnetic starter P25-2 with
its contacts.
After the starter and undervoltage relay have operated, the high-
voltage button may be released since the supply circuit of the starter
electromagnet coil is closed through the starter interlocks "A" and "B",
contacts of undervoltage relay P25-8 and normally closed contacts of over-
load relay. P25-5 (as well as the contacts of overload relay P25-8 in stations
of earlier design).
Notes Stations of earlier design are not provided with undervoltage
relay P25-8. The same reference number stands for an overload
.../relay which
SECRET
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SC!.
?
relay which is connected into the primary circuit of transformer
Tr25-4 of the +4000 V rectifier*
The interlocking circuit of magnetic starter P25-2 is closed by contacts
of relays P25-5 and P25-8. Opening of contacts of either relay causes
breaking of the supply circuit of the electromagnet coil winding of starter
P25-2 whose main contacts disconnect the supply of the high-voltage rectifier
potential regulator Tr25-7 and transformer Tr25-4 of the +4000 V rectifier.
The red pilot lamp N25-16 (HIGH VOLTAGE) goes out.
Thus, with contacts of relays P25-5 and P25-8 opened, the high-voltage
rectifier voltage and the driver output power amplifier plate supply are off.
The same will result from the operation of overload relay P25-4, from
opening of contacts bf relay 225-3 and of door interlocks W25-59 W25-69
W25-7, W25-8, W25-9 and W25-10.
In stations of earlier design Voltages from the high-voltage rectifier
and +4000 V rectifier will be switched off during operation of overload
relay P25-9 and opening of contacts of relay P23-1 located in the driver unit.
When contacts of relays P253 and P25-4 or (in the sets of earlier
1111 design, P25-9 and P23-1) or contacts of door interlocks W25-5 - W25-10 ate
open, only magnetic starter P25-1 is disconnected, because the contacts of
the above relays and door interlocks are placed in the supply circuit of
the electromagnet coil winding.
In this case the main contacts of magnetic starter P25-1 disconnect
the supply of transformer Tr25-9, transformer Tr23-4 in the driver unit,
the electromagnet coil windings of relay P25-7 and as a result green pilot
lamp N25-15 (BIAS AND SCREEN) goes out.
Thus, opening of contacts of any relay (P25-4 and P25-3 or in the sets
?of earlier design also the relays P25-9 and P23-1) or one of the door inter-
locks results in disconnection of magnetic starters P25-1 and P25-2 and
consequently in disconnection of all the rectifiers of the transmitting
system, except for the bias rectifier, -230 V, located in the driver unit.
SECRET
.../When the
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OW RE. I
- 58 -
When the electromagnet coil windings of relay P25-7 are de-onergized
?its operating contacts, through which capacitors 025-99 .025-10 and 025-5
are charged, close.
Potential regulator Tr25-7 whose voltage is fed to the primary winding
of plate transformer Tr25-6 of the high-voltage rectifier is controlled by
the knob situated on the front panel of the modulator-oscillator unit.
When turning the potential regulator knob Clockwise the voltage
applied from the autotransformer to the primary winding of plate transformer
Tr25-6 increases, therefore, the reCtified voltage rises. When turning the
potential regulator knob counter-clockwise the voltage from the high-voltage
rectifier deci.easee. TO limit the turning angle of the potential-regulator
rotrr mechanical stops are arranged on the rotor teXtylite gear in two
extreme positions of the potential regulator.
?
?
Time Relay
The time relay serves to close one of the branches of the control,
interlocking and signalling circuit of the transmitting system with a time
delay of 45 sec. The presence of the time relay makes it possible to warm
up the cathode of all valves in the transmitting system before switching on
the plate voltages.
The transmitter unit employs an electron time relay based on valve
V25-23 (6N8S). In sets of earlier design there is used an electromechanical
time relay P23-1.
Electron TIELaLly
All elements of the electron time relay are mounted on a plastic board
with a metal case. The general View of the electron time relay is shown
in Fig.449 a, and the key diagram - in Fig.449 b.
The electron time relay is supplied by the driver bias rectifier, -230 V.
Heater transformer Tr25-11 is fed with a voltage of 110 V9427 c.p.s. After
switch W25-1 has been on9 110 V, 427 c.p.s. are applied to transformers
.../Tr25-11 of
SECRET
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? 59 ?
Tr25-11 of the electron time relay and Tr23-3 of the bias rectifier, -230 V,
located in the driver unit.
By the action of the rectifier output voltage a small plate current
flows through valve V25-23 of the electron time relay. The current
circuit is closed through the electromagnet coil winding of individual point
relay P25-6, valve V25-23 and resistor 1125-60. A voltage drop of definite
polarity is developed across resistor R25-60 (Fig.44, b). Capacitor
025-19 is not able to charge instantly and this voltage will appear to be
impressed between the cathode and the grid of the valve, minus on the grid.
This results in clipping the current flowing through valve V25-23 of the
electron time relay, and consequently through the electromagnet winding of
individual point; relay P25-6.
This current is initially smaller than the operating current of the
individual point relay 125-6. As charge is placed on capacitor 025-19
(through resistors 1125-61, 1125-62 and 1125-63) the negative voltage between
the cathode and control grid of valve V25-19 decreases, while the current
flowing through the valve and consequently through the coil winding of the
individual point relay electromagnet increases. At the instant when the
current flowing through the coil winding of the individual point relay
electromagnet becomes equal to the operating current of the relay, the latter
will operate to close its normally opened contacts in the supply circuit
of magnetic starter P25-1.
The value of the time constant for the charging circuit of capacitor
025-19 and resistor 1125-60 is selected in such a way that the time relay
operates 45 sec. after switch W25-1 has been on.
When switch W25-1 is off the operating contacts of individual point
relay P25-6 come back to the initial position.
The circuit of the electron time relay enables-to increase the time
delay of the relay operation. To extend it from 45 sec. to 2 min. resistor
1125-63 should be removed from the circuit.
SECRET
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.../Electromechanical Relay
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ablAti
- 60 -
?
?
?
?
Electromechanical Relay
The general view of the electromechanical time relay is shown in
Fig.449 c.
The circuits of the electromagnet and motor of the time relay are
supplied with 220 V, 50 c.p.s. A.C.
When current flows through the coil of electromagnet 1 its core is
pulled into the coil and turns the upper lever shaft coupled to it. In
this case sprocket 10 of the upper lever comes in mesh with-sprocket 4 of
the reduction gear. Simultaneousjy with switching on the electromagnet
motor 2 whose winding is in parallel with the coil of the electromagnet
starts operating. The motor rotation is imparted through the reduction
gear andtwo sprockets 4 and 10 to lever 8 which, while turning about shaft
149 reaches the bent lug of dial 5 and on further rotation carries the dial
elmg,Adthito A stop secured on the dial disc presses latch 11 which releases
lower lever 7. The lower lever acted on by compressed spring 9 moves down
thus closing contacts 12 of the external circuit and opening contacts 13
placed in the supply circuit of the electric motor winding.
With the electromagnet voltage supply switch off the entire system is
returned to the initial position by the action of the springs.
The relay is set at the required operation time delay by increasing or
decreasing the length lever 8 travels until it engages the bent lug of the
dial.
To set the relay at the required operation time delay it is necessary
to pull the spring so that its bent end slips out of the slot in the-dial
disc. Then the disc should be turned to match the spring bent end with
the dial slot against which the required time delay is marked.
SECRET
.../Chapter 3
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LUVIL
-61-
Chapter3
ANTENNA-FEEDER SYSTEM
1. GENERAL
The antenna-feeder system of the station is designed for conveying the
electromagnetic energy produced by the magnetron, radiating it in a narrow
beam into space as well as for picking up returned signals (echoes) and for
passing them to the input of the receiving system.
The antenna-feeder system ensures unlimited scanning of space in
azimuth and in sector and from -0-50 to +14-50 in elevation.
The antenna-feeder system is hermetically sealed. lhen the station
is operating the dried air forced under a low pressure by the automatic air
dryer (dehydrator) flows through the antenna-feeder system. This air
enables the equipment to operate in any weather and causes the feeder line
to pass the required power of electromagnetic energy with the minimum
attenuation in the feeder.
The antenna-feeder system provides for:
- channelling of electromagnetic energy during transmission or reception
within the band of operating waves of the station: 10.5 to 11.1 cm;
- transmission of peak power up to 250 kW during the pulse at travelling
wave ratio not less than 0.65;
- forming the radiation pattern. Width 0-83, determined as an angle
between the directions in which the radiation power equals one half of the
power radiated in the direction of maximum radiation power.
2. BLOCK-DIAGRAM OF APTENNA-FEEDER SYSTEM
The antenna-feeder system, a block-diagram of which is shown in Fig. 45,
consists of the following basic parts:
antenna 1 which includes antenna head 11 and parabolic reflector 12;
radio-frequency coaxial feeder 2 made of separate sections coupled with
the help of fixed and rotating joints 7, 9, 10;
SECRET
.../antenna change-over
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UMONMIA
? 62 ?
?
?
?
antenna change-over switch 3, which includes the transmitter T-junction
6 and T.R. cell 4.
The antenna is designed to radiate electromagnetic energy in a narrow
beam into space as well as to pick up the signals returned from the targets
within the range of this beam.
A single antenna is used for reception and transmission.
The antenna head is arranged in front of the parabolic reflector in
such a manner that its radiation centre is in the focal plane of the
reflector.
To create cone scanning employed during automatic tracking of the target,
the radiation pattern axis is slightly tilted in relation to the geometrical
axis of parabolic reflector and traces of cone surface during the antenna
head rotation.
The radio-frequency coaxial feeder is designed to convey electromagnetic
energy with minimum loss from the transmitter to the antenna and from the
antenna to the receiver.
Two rotating joints- azimuth joint 7 and elevation joint 9 called
slow rotating joints are similar in design. They provide passing of
electromagnetic energy through the feeder during rotation of the antenna in
azimuth and elevation.
The third rotating joint 10 called a fast rotating joint slightly
differs in design from the above two. It provides transmission of energy
when the antenna head rotates at a speed of 1440 r.p.m. which is required
for cone scanning of the beam.
The antenna change-over switch is designed to protect the receiver
from damage by the transmitter powerful pulse.
The antenna change-over switch consists of T.R. cell 4 with a spark
gap and transmitter T-junction 6 which is represented by a T-connection of
the coaxial feeder, which connects the feeder with the magnetron and T.R.
cell.,
SECRET
, .../During the
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?
?
?
-63-
During the transmitter operation T.R cell 4 keeps the transmitter
powerful pulses out of the receiver thereby protecting the receiver from
damage.
In the transmitter resting time the T.R. cell performs the function of
the input circuit that couples the antenna to the receiver.
3. BASIC NOTES ON THEORY OF ULTRA-SHORT WAVE
TRANSMISSION LINES
In ultra-short wave transmission lines energy propagates along the line
in the form of voltage and current waves.
Energy propagates along the line with the final velocity. During one
oscillation cycle energy moves along the line to cover the distance equal
to the wave length.
In case energy moves along an infinite line the voltage and current waves
are in phase along its entire length, therefore, the relation of voltage to
current in any point of the line remains constant and equal to the line
characteristic impedance. The characteristic impedance depends upon the
form and sizes of the line cross-section; the coaxial line characteristic
impedance is determined by the formula
p = 138 lg _3_ ,
where D is the internal diameter of the external tube,
d is the external diameter of the internal tube.
The radio-frequency feeder used in the station is a coaxial line with
dimensions: D . 20 mm, d = 9 mm; its characteristic impedance is
p = 138 lg = 48 ohms.
In the real finite line loaded by resistance equal to the line
characteristic impedance the same wave propagation conditions as in the
infinite line occur.
If the line is loaded to a resistance unequal to the characteristic
impedance the energy is partially absorbed by the load resistance and is
.../partially reflected
MUT
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mitiretnrw
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?
?
- 64 -
partially reflected from the load back into the line. In this case two
waves, i.e. voltage and current waves move along the line: one towards the
load, the other from the load, the first wave exceeding the second in
amplitude.
As a result of addition of these two waves the voltage amplitude value
periodically varies along the line.
Such a mode of operation is characterized by travelling wave ratio,
expressed as a relation of the iilinimum amplitude value to maximum amplitude
value. The energy absorbed by the load will be greater with a higher
travelling wave ratio.
The radio-frequency feeder of the station is a finite line loaded by
the antenna input resistance which is approximately equal to the feeder
characteristic impedance.
The antenna input resistance varies depending upon the frequency but
the travelling wave ratio within the band of operating waves (10.5 to 11.1 cm.)
in the antenna-feeder system is not less than 0.65.
In an open or short circuited finite line without loss (or with small
loss) complete reflection takes place (Fig.46). In this case the amplitude
of the voltage wave travelling from the generator to the load is equal to
the amplitude of the wave travelling back over the line towards the generator.
Therefore, their addition produces voltage and current standing waves in the
line.
This mode of operation is characterized by sine variation of voltage
amplitude value and cosine variation of current amplitude value along the
line.
At the end of the short-circuited line the voltage equals zero, the
X
current is maximum at a distance of from the end of the line the
voltage is maximum and the current equals zero. Consequently, the input
resistance of the quarter-wave short-circuited line which equals tite voltage-
to-current ratio is infinitely large.
grAFT.../It follows
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etrrina
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- 65 -
It follows from this that the quarter-wave short-circuited line,
connected to the generator, is equivalent to an insulator as regards its
effect on the fundamental wave length, because the line input resistance
equals infinity. This property of the quarter-wave short-circuited lines
is the basis of the action of T-shaped insulators of the antenna feeder
system.
At the end of the quarter-wave open line the current equals zero while
2\.
the voltage is maximum; at a distance of 7- from the line end the voltage
equals zero and the current is maximum. Consequently, the resistance at
the input of the quarter-wave open line equals zero.
The quarter-wave open line, connected to the generator is equivalent
by its action on the generator on the fundamental wave length to a short-
circuit since the line input resistance equals zero.
This characteristic of the open quarter-wave line is used to produce
a short-circuit between the conductors in rotating joints of the antenna-
feeder system where difficulty is experienced in establishing a direct
contact between the conductors.
4. RADIO-FREWENCY COAXIAL FEEDER,
ITS ATTACHNENT AND DESIGN
The radio-frequency feeder serves to pas powerful electromagnetic
waves from the magnetron to the antenna and the signals picked up by the
antenna to the receiver.
The design and attachment of the radio-frequency feeder is shown in
Fig.47.
Branched off magnetron 14 is sleeve 11 connected to _T-junction 12 of
a transmitter coupler to which feeder section 1 is attached. The feeder
runs inside the transmitter.
In the centre of the bottom part of the antenna pedestal foundation
the feeder has azimuth slow rotating joint 2. From the rotating joint the
.../feeder runs
SECRET
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de.viriontry
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-66-
feeder runs through the hollow shaft of the antenna pedestal and at the
41) right angle goes to elevation slow rotating joint 5.
Fast rotating joint 7 is located after tilted feeder 6.
Movable part 9 of the fast rotating joint is placed inside the frame
of reference voltage generator 8. Further the feeder runs through the
generator hollow shaft to antenna head 109 the generator motor and the
antenna head being on a common shaft and are driven by one electric motor.
Each section of the radio-frequency feeder is made of two brass tubes'
one tube being placed inside the other (coaxial line).
The current-conducting parts of the coaxial line are the inner surface
of the outer tube (20 mm in diameter) and the outer surface of the inner
tube (9 mm in diameter). These dimensions are optimum and ensure passing
of the required power at minimum energy losses in the feeder.
The electromagnetic energy conveyed b the coaxial line is enclosed
in the space between the inner and outer conductors of the line, therefore
no radiation loss can take place.
The inner conductor of the line is fixed in the middle with the aid of
quarter-wave short-circuited coaxial line sections.
,The input impedance of a short-circuited section of a coaxial line is
infinity if the length of the section equals 2?_ ofthe fundamental wave-
length Xo. If such a section is connected in parallel to the line, it
will not act as a shunt for the fundamental wavelength, i.e. it will act
as a good insulator.
If the magnetron wavelength is slightly altered, the input impedance of
the quarter-wave insulator will decrease, the quarter-wave insulator will
shunt the transmission line, and part of the energy will be reflected from
? the junction.
In order to obtain a stabilized operation of the magnetron, and full
transmission of energy along the line, the travelling wave ratio in the
line should be not less than 0.65 for the whole range of the operating
frequencies of the set (10.5 - 11.1 cm.). emu?
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CTPorr
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- 67 -
As the shunting effect of the insulators appears at the extrume
wavelengths of the operating frequency range of the set, in the transmission
line, together with the quarter-wave insulator, use is made of a half-wave
transformer formed by a section of the internal conductor which has an
increased diameter (Fig.48).
The half-wave transformer serves to compensatefor the reflection
introduced into the line by the quarter-wave insulator at the wavelengths
which differ from the fundamental.
The input impedance of the half-wave transformer equals the load
impedance connected to its output. That is why for the fundamental
frequency the half-wave transformer has no influence upon the energy
transmission along the line.
Therefore, for the fundamental wavelength neither the insulator, nor
the transformer introduce any reflections into the line.
If the feeder operates on a wave length below the fundamental one
(N X0) the insulator inserts reflection in the line as its input
impedance is not infinitely large. In this case the insulation is a
capacitive load connected to the feeder.
In this case the half-wave transformer inserts reflection in the line
as well. Its action is equivalent to that of an inductive load and with
the half-wave transformer acting on the feeder line, their action is being
compensated mutually and partially.'
Similarly compensated are reflections inserted in the line by the
insulator and transformer on wave lengths above the fundamental one
(N X0). In this case the insulator is equivalent to the inductive
load, while the transformer in the first approximation is equivalent to the
capacitive load.
When the diameter of the transformer inner conductor is properly
selected reflections in the line (mismatch) caused by the quarter-wave
.../insulator and
SECRET
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OLADIU..
- 68 -
?
?
insulator and half-wave transfoiver may be Mutually compensated for within
the entire operating. Wave bandefAhe. station-.
Besides T-shaped insulators, bend-type insulators (Fig.49)
are used in
the feeder bends of the antenna-feeder system. This insulator consists
of a short-circuited stub (quarter-wave insulator) 2 and quarter-wave
transformer 4.
The quarter-wave transformer which is essentially a line- section with
a decreased diameter of the inner conductor, affects the operation of the
feeder onthe fundamental wave (inserts reflections).
To compensate for
this affect the length of the short-circuited stub is made
A 0
*
throughout the entire operating wave band of the station.
Such design of the angle provides compensation of
smaller than
reflections
To rotate the antenna in azimuth and elevation and the antenna head
without disturbing electrical coupling in the feeder provision is made for
two slow and one fast rotating joint.
The design of the elevation slow rotating joint is shown in Fig.50.
The inner races of ball bearings 1 and 2 are connected with the outer
conductor of the right-hand part of the feeder by means of nuts 53 the
outer races placed in body 14 are attached to the outer conductor of the
left-hand part of the feeder by means of screws 3. The outer conductors
are centred by ball bearings 1 and 2, while the inner conductors - by pin 6.
The azimuth slow-rotating joint is similar in design to the elevation
rotating joint and is shown in Fig. 51.
Such design of the rotating joints makes possible rotation of one
feeder part in relation to the other without disturbing their centring. In
this case no longitudinal displacement of one part with regard to the other
is possible.
To provide hermetic sealing the slow-rotating joints are furnished
with rubber washers 8 and packing collars 7.
SECRET
.../The design
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a LUPO. I
-69-
.
?
The design of the fast rotating joint is illustrated in Fig.52.
Feeder rotating joint 19 located in the inner compartment of the reference
voltage generator shaft, rotates together with the shaft. The feeder
fixed section 9 is rigidly coupled to the generator frame by means of
screws 4 and flange 3.
Hermetic sealing of the fast rotating joint is provided by rubber
washers 6, 7 and packing collar 5.
The inner and outer conductors of the rotating joint and fixed section
of the feeder overlap each other with a small constant clearance. As a
result the feeders are connected by quarter-wave stubs AB and BC, DE and FE
(Fig. 52).
Stub AB is a short-circuited line. Its input resistance, i.e. resistance
in point B, equals infinity while in point A - zero.
Stub BC is a quarter-wave line opened at the end (in point B); its
input resistance in point C equals zero.
Stub DE consists of quarter-wave short-circuited line DF and quarter-
wave open line FE; its input resistance in point E equals zero. Zero
resistances in points C and E ensure reliable transmission of energy
between the rotating joint and fixed section of the feeder.
The broad band of the rotating joints is provided by selecting
clearances between the current-carrying surfaces of the quarter-wave lines
opened and closed at the end.
An electric circuit of the rotating joints is shown in Fig. 54.
The radio-frequency feeder sections are connected to each other by
means of connectors whose design is illustrated in Fig. 55.
The end faces of the outer tubes are slightly bevelled so that a
reliable contact is obtained when they are connected. Rubber washers 5
placed between the collars ensure hermetic -sealing. The inner conductors
of the feeder are tightly coupled to each other by means of plug connectors.
.../To prevent
SECRET
,
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erto hta R. 0...24
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VIEml&) 11 ULM Sa
?
?
-70-
To prevent oxidation of contact surfaces in places of fixed oonnectors
the current-carrying surfaces of the feeder conductors are covered with a
film of gold at the ends of each section.
5. ANTENNA CHANGE-OVER SWITCH
The antenna change-over switch consists of T-junction 2 and T.R cell 1
(Fig. 55).
The T-junction (Fig.56) is an intermediate link connecting the
magnetron and the T.R. cell to the radio-frequency feeder.
The magnetron oscillator is connected with arm 3 of the T-junction
with the aid of sleeve 4 with a ring nut 11 screwed on over the threaded
part of the magnetron.
Internal conductor 12 of the coaxial output of the magnetron is
connected with the transmission line with the aid of spring contact 5.
Connection between the external conductors of the high frequency
magnetron output 8 and T-junction 9 is made with the aid of contact 4 of
the quarter-wave lino 6 and 7, which acts in the same way as the quarter-wave
sections of the rotating joints. Arm 2 of the T-junction is connected to
the T.R. cell by coupling loop 10, arm 1 to the transmission line leading
to the antenna.
The T-junction has an attenuator 13, through which part of the energy,
required for the operation of the automatic frequency control (AFC), is
branched off. The attenuator is shaped like a wave-guide section the
length and diameter of which is chosen to ensure that the high frequency
energy of the transmitter pulse is sufficiently attenuated before reaching
the mixer of the AFC.
The dimensions of arm 3 and of the sleeve (cup) 4 are chosen in such
a way that the input impedance from the side of the T-junction, with the
magnetron connected, equals infinity.
SECRET
.../There are
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uwogui..1
- 71 -
There are therefore no reflections within the T-junction, and the
411 pulse enters the T.R. cell without attenuation. The T.R. cell is tuned
?
?
to the magnetron frequency with the aid of bolts 4 (Fig. 57), and therefore
to the frequency of the pulses reflected from the target.
Inside the T.R. cell is located T-R switch (short-circuiting valve) 2
containing a special gas mixture at low pressure. Two copper discs fused
into the switch (valve) protrude outside the switch in the shape of two
parallel rings. The switch envelope is rade of glass with small dielectric
loss at ultra-high frequencies.
The copper discs (inside the valve) carry hollow discharge cones,
whose peaks are separated by a small gap. Inside one of the cones is
located keep-alive electrode 11. This electrode is supplied through a
damping resistor by the modulator bias rectifier with a voltage of about
-820 V with respect to the earthed cones of the discharger.
As a result a glow discharge of 100 to 200 microA is continuously
maintained between one of the cones and the keep-alive electrode. Due
to the glow discharge there is always a certain quantity of ionized gas
? molecules near this cone. The ionized gas between the discharger cones
facilitates the break down of the spark gap when the magnetron produces
oscillations.
Outer detachable half-rings 5 of the T.R. cell resonator fitted on
copper discs 10 of the discharge valve form a cavity circuit together with
the valve.
The T.R. cell cavity circuit is coupled to the crystal mixer by means
of coupling loop 12, while to the T-junction by coupling loop 13.
The degree of coupling of the cavity resonator with the mixer or
T-junction depends upon the loop area and its orientation in relation to
the resonator axis.
During reception a variable electromagnetic field is built up in the
resonator cavity (cavity circuit) tuned to the magnetron frequency and
SFITET
.../therefore. to
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OLU1110..
?
?72?
therefore, to the carrier frequency of the echo signal. This field
induces the E.M.F. in the mixer coupling loop.
? This is the way electromagnetic energy is transmitted from the loop
of the T?junction to that of the mixer, i.e. from the antenna to the
crystal mixer. The magnitude of the transmitted energy depends upon the
accuracy with which the cavity circuit is tuned to resonate with the
magnetron frequency. If the cavity circuit is considerably detuned,
transmission of electromagnetic energy from one loop to the other becomes
practically impossible. Therefore the radar detection range is largely
dependent on the tuning of the cavity circuit and its coupling to the
receiver mixer.
The operation of the T.R. cell during reception at frequencies
approximating the resonant frequency, may be illustrated by an equivalent
diagram presented in Fig.57, c.
During the magnetron operation the T.R. cell functions differently.
Part of the transmitter pulse energy is passed through the coupling loop
to the T.R. cell 3 in this case a great A.C. voltage is developed between
the discharger cones which causes breakdown of the gap between them. Due
to the breakdown the T.R. cell cavity circuit is detuned and as a result
the conditions of energy transmission from the coupling loop of the T?junction
to that of the mixer are impaired. However part of the energy penetrates
to the receiver and the tube screens of the range and plan?position indicator
display a direct pulse marker.
To neutralize the T.R. cell affect on energy transmission towards
the antenna the length of the arm connecting the T.R. cell to the radio?
frequency feeder should ensure the infinity of the arm input resistance on
? the T?junction side with the detuned T.R. cell connected to it.
The gap between the cones is broken down at the instant the magnetron
begins to generate and the discharge continues as long as there is generation.
...After the
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AIL MI elAL ISA IPMS15
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?
?
?
After the magnetron has stopped operating the discharge between the cones
ceases and the cavity circuit is returned to its initial resonance state.
6. ANTENNA
The antenna is composed of a parabolic reflector and an antenna head.
The parabolic reflector is a rigid metal structure. The paraboloid
reflecting surface is perforated to decrease its weight and wind resistance
without a noticeable change in rigidity and reflecting power. The diameter
of the reflector is 1.5 m., and the focal distance is 0.441 m.
The parabolic reflector is oriented with regard to the reference
voltage generator in such a manner that its geometrical axis coincides with
the axis of the antenna head rotation.
The antenna head (Fig.58) consists of half?wave asymmetrical dipole 1,
reflecting disc 2, quarter?wave transformer 7 and quarter?wave bazooka 8.
One half of the dipole is attached to the outer conductor of the feeder, the
other half to the inner conductor and passes through a hole cut in the outer
conductor.
The reflecting disc is a brass disc fixed to protruding part 11 of the
antenna head feeder. The feeder protruding part is a short?circuited
stub and serves to secure the inner conductor of the antenna feeder.
The dipole, quarter?wave bazooka and reflecting disc are placed in
polistyrene housing 6, which is required to make the antenna feeder
hermetically sealed.
To blow the antenna head with dry air provision is made in the
protruding part of the inner conductor for hole 5 which during operation is
closed with cap 3.
The dipole intended for radiating the parabolic reflector is connected
asymmetrically to the radio?frequency feeder. One rod of the dipole is
directly connected to the current?carrying surface of the feeder conductor.
The other rod is connected to the current?carrying surface of the feeder
second conductor through the edges of the hole in the tubular conductor
SECRET .../and through
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CW,m611
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and through the tubular conductor outer surface elements located near the
hole.
Asymmetrical excitation of the dipole results in asymmetrical (in
relation to the axis of the head rotation) distribution of electromagnetic
energy radiated by the dipole, thus, the dipole centre of radiation being
displaced in relation to the axis of rotation towards the rod connected to
+he outer conductor.
That part of radiated energy which falls on the reflecting disc is
directed towards the parabolic reflector. The parabolic reflector
concentrates it into a narrow beam and directs it into space. Thus, more
high gain faclor of the antenna in the direction of the axis of the radiation
pattern is obtained. Due to leakage of electromagnetic energy through
the hole in the outer conductor and due to direct connection of the
conductor external surface to one of the dipole rods high-frequency currents
are developed on the outer conductor external surface. These currents may
travel over the outer conductor towards the parabolic reflector and distort
the radiation pattern.
To keep these currents out of the parabolic reflector a quarter-wave
bazooka with an input resistance equal to infinity is fitted over the outer
surface of the feeder.
The parabolic reflector concentrates the energy radiated by the antenna
head into a beam, whose axis is tilted with respect to the reflector axis,
because the antenna head centre of radiation is slightly displaced from
the reflector axis.
When the antenna head is rotated the position of the beam in space
changes and its axis traces a cone surface. The radiation intensity is
maximum in the direction of the beam axis and decreases away from the axis.
The radiation intensity in various directions is characterized by
the radiation pattern shown in Fig. 59.
SDI
...At should
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?
It should be noted that at small elevations of the parabolic reflector
with regard to the earth's surface, a considerable part of the energy
radiated by the antenna strikes against the earth surface, which is rather
a good reflector for ultra-short radio waves.
As a result of the imposition (interference) of radio waves radiated
into space direct from the antenna and reflected from the earth's surface
the antenna radiation pattern sharply changes, and breaks (in vertical
plane) into a number of lobes.
Consequently, with the angles between the target direction and earth
surface level below 1-00 the accuracy of the target tracking in angular
coordinates drcreases and at a certain value of the angle the automatic
target tracking is out of the question.
The input resistance of the antenna is matched with the output
resistance of the radio-frequency feeder by means of quarter-wave transformer
7 (Fig.58) designed as a boss of the feeder inner conductor.
It should be borne in mind that matching of the antenna with the feeder
and inclination of the radiation pattern axis with respect to the geometrical
axis of the reflector are largely dependent upon the distance between the
dipole and quarter-wave bazooka 8, upon the distance between the dipole and
the reflecting disc as well as upon the length of the short-circuited stub
in protruding part 11 of the feeder. Therefore, any arbitrary alterations
in dimensions and mutual location of separate elements of the antenna head
are not allowed.
The input resistance of the antenna, dependent upon the position of
the quarter-wave bazooka and reflecting disc with regard to the reflector
as well as upon the length of the short-circuited stub, changes with the
alteration in frequency. This results in decrease of the TWR of the
antenna-feeder system.
The length of the short-circuited stub, the distance from the dipole
to the quarter-wave bazooka and reflecting disc should ensure variation
SECRET
.../of the
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of the antenna input resistance (with the change of frequency) within the
? range providing the TWR is not below 0.65. At the same time the deflection
angle of the beam axis in respect of the reflector axis is about 0-23.
?
Chapter4
RECEIVING SYSTEM
1. GENERAL
The receiving system serves to convert and amplify the target echo
signals picked up by the antenna to a magnitude required for normal
observation of these echo markers on the screens of the range and plan-
position indicators as well as for operation of the automatic range finder
units and the antenna positioning system.
The receiving system consists of a signal mixer, an automatic
frequency control (AFC) mixer, and three units 3 an intermediate-frequency
preamplifier, an automatic tracking channel amplifier and a range channel
amplifier.
Both mixers are coupled with the elements of the antenna-feeder system.
The intermediate-frequency preamplifier unit is located in the transmitter
cabinet, whereas the remaining units - in the cabinet of the main control
board.
The receiving system utilizes a superheterodyne circuit. To maintain
constancy of differential frequenby of the local oscillator and the
magnetron in the course of operation the receiving system is provided with
automatic frequency control (AFC).
2. BLOCK-DIAGRAM
Electromagnetic pulses of ultra-high frequency (2700 to 2860 Mc/sec.)
returned from the target as echoes are picked up by the antenna and
conducted through the antenna feeder and T.R. cell to the signal mixer
SECRET .../(Fig.61).
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or Rule
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?
?77?
(Fig.61). The mixer is also supplied by the microwave local oscillator
with voltage of sustained oscillations having a frequency which differs
from the picked-up by the value of the intermediate frequency of 30 Mc/sec.
These two frequencies are heterodyned within the mixer to produce I.F.
voltage. This voltage, amplified by three stages (V22-8, V22-9, V22-10)
of the preamplifier located in the I.F. preamplifier unit, is applied to
the automatic tracking channel amplifier unit through the radio-frequency
cable.
The signal is furnished to the AFC mixer from the transmitter through
a cut-off attenuator which ensures the required pulse attenuation. The
AFC mixer is also supplied by the microwave local oscillator (V22-22) with
voltage of sustained oscillations having a frequency differing from the
frequency of the echo oscillations by the value of the intermediate
frequency of 30 Mo/sec. These two frequencies are heterodyned within the
mixer to produce I.F. voltage of 30 Mc/sec. The AFC mixer output is
applied to the I.F.A. input of the AFC channel, amplified by three I.F.A.
stages (V22-1, V22-2, V22-3) and is furnished to the discriminator
(frequency-sensitive detector V22-4). The discriminator produces a voltage
whose value is proportional to the deviation of intermediate frequency of
30 Mc/sec from the rated, while the voltage polarity depends upon the sign
of drift of intermediate frequency in relation to its rated value of 30 Mc/sec.
This voltage amplified by the pulse amplifier (V22-5) acts on the control
circuit formed by diode V22-6 and a saw-tooth oscillator - a phantastron
(V22-7). The output voltage of the control circuit controls the frequency
of the klystron oscillator so that voltage of the rated intermediate
frequency of 30 Mo/sec is obtained at the output of the signal mixer.
The I.F. preamplifier unit accommodates a local oscillator (V22-22)
with stabilized rectifier -250 V (V22-14 to V22-18) and -255 V, V22..-19 to
V22-21), and a +150 V rectifier (V22-11) supplying the stages of the I.F.
preamplifier and some stages of the AFC channel.
SECRET
.../In the
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In the automatic tracking channel the I.F. signal is amplified by four
? I.F.A stages (V1-1, V1-2, V1-3, V1-4) which are the fourth, fifth, sixth and
seventh stage of the I.F.A. of the receiving system. After the fourth
(seventh) stage the signal travels along the two channelsg automatic
tracking and range channels.
The automatic tracking channel is triggered only when the very narrow
gate of 0.3 microseconds duration furnished from the range unit is acting
on the fifth (eighth) intermediate-frequency amplifier stage. Therefore,
411 the automatic tracking channel passes only those pulses which are
synchronized with the very narrow gate. The signal in the automatic
tracking channel is amplified by two I.F.A. stages (V1-5, V1-6) detected by
the diode detector (V1-7) and amplified by two video amplifier stages
(V1-8, V1-9). From the output of the video amplifier (V1-9) the amplified
negative pulses are applied to the automatic gain control circuit and to the
automatic tracking and automatic range finder units.
The automatic gain control (AGC) circuit is designed to maintain a
constant amplitude of the signal at the output of the receiving system.
? This is required for proper operation of the antenna positioning system.
If the input signal is largely varied, the output voltage of the AGC circuit
changes the bias voltage on the control grids of the first (fourth) and
second (fifth) I.F.A. stages (V1-1, V1-2) in such a way that the level of
the receiving system output remains approximately constant.
Apart from the above stages, the amplifier unit of the automatic tracking
channel accommodates one I.F.A. stage of the range channel (V1-11) whose
output signal is furnished to the input of the range' channel amplifier unit,
and a stabilized voltage rectifier, +120 V, (V1-12 - V1-15) to supply some
valves of the I.F. amplifier (V1-1 to V1-5, V1-11).
In the range channel amplifier unit the signal is amplified by an
I.F.A. stage (V2-1), detected by the diode detector (V2-2), amplified by
SECRET .../three video
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UNA6MLI
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three video amplifier stages (V2-3, V2-4, V2-5) and is conducted to the
range indicator unit, plan-position indicator unit and automatic range
finder unit.
The range channel amplifier unit contains rectifiers for +300 V
(V2-7, V2-8) and for -105 V (V2-9) which are used to supply the valves of
the given unit and of the amplifier unit in the automatic tracking channel.
3. SIGNAL AND AFC MIXERS
The signal mixer (Fig.61) is located between the T.R. cell and the
microwave local oscillator and is rigidly coupled with the T.R. cell by
means of plate 11 secured with screws.
The signal mixer includes: cartridge 1 with a germanium mixer diode
(type DG-S1) inserted into coaxial line 2 which is connected to the T.R.
cell by means of . . (one whole page missing)
To obtain the required sensitivity of the receiving system it is
necessary to choose an operating point with maximum steepness on the
current-voltage characteristic of the crystal diode, since in this case the
required conversion factor is provided.
The i)osition of the operating point is determined by optimum value
of the crystal diode current which in turn is determined by the power
applied from the oscillator (as the signal power is very small and practically
does not affect the crystal current).
The crystal diode current should be selected at minimum coupling with
the oscillator and at maximum matching of the oscillator with the mixer.
Minimum coupling with the oscillator is achieved by lifting up capacitive
disc 7 when adjusting screw 5 is rotated counter-clockwise. The oscillator
is matched with the mixer by selecting a definite length of the connecting
line with the help of trombone 4.
Thus by selecting the above values the Oscillator may be caused to
produce maximum power output at sufficiently weak coupling with the mixer
.../and at
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and at the required current of the crystal diode (optimum current value is
? within the range of 0.2 to 0.6 mA). This results in reduction of the signal
energy loss in the oscillator circuit. Besides, minimum noise voltage
from the oscillator pcnetrates into the mixer.
The AFC mixer (Fig.62) is screwed on the cut-off attenuator which is
rigidly coupled with the T-junction of the feeder line by means of a nut 7.
The mixer includes: cartridge 1 with a crystal diode of the DG-S1 type,
placed in coaxial line 2, which is coupled to the cut-off attenuator with
the aid of coupling loop 3; 50-ohm washer 4 used to match the mixer with
the microwave oscillator; coupling adjusting screw 5 output connector 6
which accommodates a R.F. filter.
The AFC mixer is similar in the operating principle to the signal mixer.
Coaxial line 2 is provided with a nut 7 by means of which the mixer is
moved along the cut-off attenuator.
110 The cut-off attenuator comprises a section of a cylindrical waveguide
having great attenuation for the transmitter frequency band. The value of
the transmitter signal attenuation is proportional to the waveguide length.
? The signal value required for the normal operation of the AFC channel
is selected by shifting the mixer so as to achieve the most advantageous
position of the coupling loop in the attenuator.
The matching of the coupling line of the mixer with the oscillator by
means of the 50-ohm washer makes it possible to obtain the crystal diode
current of not less than 0.2 mA in the operating frequency band of the
station, which is enough for the mixer normal operation. The AFC mixer
should not be highly sensitive, as the value of the signal applied to the
mixer can be regulated by varying the position of the mixer coupling loop
in the cut-off attenuator.
The cut-off attenuator (Fig.63) is designed as a cylindrical tube
(waveguide) soldered at an angle of 300 to the coaxial feeder.
.../4. INTERMEDIATE-FREQUENCY
MR,
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tamaufEra....
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?
?
4. UTEREEDIATE-FREQUENCY PREAMPLIFIER (I.F.P.) UNIT
The I.F.P. unit is located in the transmitter cabinet. The unit
chassis carries a microwave oscillator with a supply rectifier, an I.F.
preamplifier and elements of the AFC channel.
A key diagram of the I.F. preamplifier unit is shown in Fig.64 (see
Album). The front panel of the unit is presented in Fig.65, while its
top view - in Fig. 66.
Microwave Oscillator
The microwave (klystron) oscillator serves to produce radio-frequency
sustained oscillations having a frequency differing from that of the
magnetron Iv the value of the intermediate frequency of 30 Mc/sec within
the operating frequency band of the transmitter (2700 to 2860 Mc/see.).
The radio-frequency oscillator connected as a microwave oscillator
'(Figs 679 68) consists of a special valve, called klystron, and e cavity
circuit (resonator).
The circuit is formed by part of the cavity enclosed between the grids
inside the klystron and metal body 4 of the cavity circuit, in which the
klystron is encased.
The kiystron, type K-119 used in the station consists of a heated
cathode, a control (accelerating) grid, two resonator grids and a repeller.
The klystron control grid connected with the resonator grids and the
cavity circuit is supplied from the stabilizer output with a positive
(with respect to the klystron cathode) voltage of +250 V. The repeller is
fed with a negative (with respect to the cathode) voltage adjustable from
-40 to -170 V.
The klystron functions as follows;
Electrons emitted from the cathode are accelerated by the positive
potential on the control grid until they enter the space in
the central part of the resonator (cavity circuit).
SECRET
the cavity of
After that they pass
.../between the
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between the two resonator grids. A variable electric field of radio-
frequency oscillations set up in the cavity circuit at the instant when the
klystron is switched on or due to fluctuation of the electron flux density,
accelerates the electrons for one half-cycle and retards them for the
second half-cycle.
In connection with it some electrons travel into the space between
the resonator grids and the repeller with increased velocity vo + v1 while
others with decreased velocity vo vl.
The electrons that pass between the resonator grids at the instant
when the variable field is zero travel into the space between the grids and
the repeller with the same velocity vo, which have all the electrons
approaching the resonator grids.
Thus, after passing the resonator grids the electrons in the beam
appear to be velocity-modulated. In the space between the resonator grids
and the repeller the electrons are acted on by the field of the repeller
electrode chargad negatively and tending to return the electrons back to
the resonator grids. The electrons with different velocities have
different trajectories in the drift space. The electrons with higher
velocities approach the repeller closer than those with lower speeds. At
a definite relationship of voltages across the klystron grids and the
reoeller, the electrons with both higher and lower velocities return to
the resonator grids simultaneously (Fig.69). Thus, velocity modulation
of the electron flow converts into density modulation.
Separate bunches of electrons formed as a result, while returning to
the grids of the resonator give up part of previously stored energy to it.
This occurs during the half-cycle of oscillations when the resonator
electric field retards the motion of electrons towards the cathode.
From this it can be seen that sustained oscillations in the klystron
may be excited at definite matching of the transit time from the resonator
SECR .../grids to
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auoutu.0
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grids to the repeller and backwards with a cycle of the resonator self-
oscillations.
At the assigned oscillation frequency of the resonator this matching
is achieved due to the change of potential on the klystron repeller.
The oscillator frequency depends upon the dimensions of the cavity
circuit (resonator). The change in the circuit cavity is obtained by the
aid of four threaded plugs 8 (Fig.68) inside the resonator. By these plugs
the oscillator is tuned to the required frequency and the frequency is
adjusted when the magnetron is replaced.
The fifth plug .(11) is coupled to knob 9 which is brought out to the
front panel of the unit and is marked KLYSTRON FREQUENCY. By means of this
plug the oscillator wavelength is regulated at any section of its operating
band within the range of not less than 0.2 cm.
The cavity circuit of the klystron incorporates three coupling loops.
Two of them are used to conduct the radio-frequency power through coaxial
cables to the crystal signal and AFC mixers. The third loop is connected
through the coaxial cable to the connector located on the front panel and
marked CONTROL CONNECTOR. The connector is coupled to the echo box by
means of which the oscillator frequency is measured.
Presence of current in the circuit of mixers is determined by instrument
Pp22-1 (CRYSTAL CURRENTS) situated on the front panel of the I.F. pre-
amplifier unit (Fig.65). To Measure the crystal currents of the signal
and AFC mixers the instrument is switched over by means of selector switch 9
marked CRYSTAL CURRENTS (W22-3). Maximum power is taken from the klystron
when the coupling loop is located in the vertical plane.
Sustained oscillations may be maintained in the klystron at several
different voltages impressed on the repeller.
The klystron, type K-11, employed in the station has within the
operating band two or three regions of generation to which correspond the
.../following potentials
. lECR,
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following potentials on the repeller (relative to the cathode);
first region from -20 to -40 V;
second region from -50 to -140 V;
third region from -170 to -250 V.
The value of maximum power produced by the klystron, and the range of
electronic tuning change depending upon a region of generation (Fig.70, a, b).
For klystrons, type K-11, the second region of oscillations is the
most stable. It has higher power and wider range of electronic tuning as
compared with the first and third regions. Therefore, the range of
voltage regulation on the repeller is selected (from -40 to -170 V relative
to the cathode./ so as to excite oscillations of the second region, the
first and third regions being used partially.
To achieve high stability of the frequency of oscillations the repeller
and the resonator of the klystron are fed with stabilized voltages.
Voltage is applied to the klystron repeller through a divider formed
by resistors R22-58 and R22-60 which are connected to the sliders of
potentiometers R22-56 (REPELLER VOLTAGE) and R22-59 (ZONE SELECTION).
These potentiometers are in parallel with stabilovolts V22-20 and V22-21
which stabilize the voltage' from a -255 V rectifier employing valve V22-19
(5C4S).
The klystron resonator is fed with a stabilized voltage of +250 V
(relative to the cathode) from an electronic regulator utilizing valves
V22-16, V22-17 and V22-18 (Fig.71).
The input of the electronic regulator is fed with voltage from the
rectifier using valve V22-14 (5C4S). The plus of the regulator is earthed
whereas the minus is connected with the klystron cathode. Valve V22-16
(6P3S) is an automatically controlled variable resistor placed in series
with the load circuit of the regulator. Valve V22-18 (6Z8) controls valve
V22-16. The rcontrol gr'd-of valve V22-18 is supplied with a portion of
the regulatorioutput voltage from the slider of potentiometer R22-50
.../RESONATOR VOLTAGE
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?
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RESONATOR VOLTAGE SETTING placed in the circuit of a dividerformed by resistors
R22-491 R22-50, R22-51. This divider is connected in parallel with the load.
If, for some reason, the output voltage increases, the potential on
the grid of valve V22-18 rises with resultant rise of the plate current of
valve V22-18 and increase of the voltage drop across resistor R22-45.
The plate voltage of this valve decreases. The voltage on the control
gid of valve V22-16 decreases, since it is connected through resistor
R22-46 with the plate of the control valve. This lends to an increase of
differential resistance of valve V22-16 and to an increase of the voltage
drop across it, and consequently to redistribution of the voltage applied
from the rectiiier between valve V22.,-16 and tha load. In this case the
voltage across the load decreases to the rated value.
If the output voltage decreases an opposite process takes place.
The cathode of control valve V22-18 has a constant potential of +150 V
due to voltage drop across regulator V22-17 (504S). This has been done
to ensure more complete transmission of changes in the output voltage to
the grid of the control valve and simultaneously to ensure normal bias on
its grid (otherwise the grid would be under high positive potential
relative to the cathode).
Capacitor C22-44 is designed to raise the efficiency of the regulator
circuit with regard to quick fluctuations of the regulator output voltage
caused by a quick change in load current
with a frequency in the region of dozens
capacitor 022-44 has a low resistance as
the
or output voltage.
At changes
of cycles per second or more,
compared with the resistance of
upper arm of the divider formed by resistors R22-49, R22-50, R22-51.
As a result, the A.C, eomponents of the output voltage are almost entirely
applied to the control grid of valve V22-18.
n The regulator output voltage can be adjusted by shifting the slider
of potentiometer R22-50. The shaft of potentiometer R22-50 is brought
.../out to
SECREI
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OUJUN4kia.
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out to the front panel and is marked RESONATOR VOLTAGE SETTING (Fig.66).
By rotating this shaft, the voltage on the cathode-resonator section of
the klystron, meaSured between monitoring jack G22-2 (-250 V) and the
chassis, is set equal to -250 V.
The receiving system can function in two modes of operation: automatic
frequency control and manual frequency control. The desired mode is
selected by means of switch W22-4 whose knob is brought out to the front
panel of the I.F. preamplifier unit and is marked MANUAL - AFC (8, Fig.65).
When the station is operating, the knob should be set in position AFC,
since in the course of operation, especially immediately after the start,
the frequency of the klystron and magnetron maj greatly change which would
necessitate frequent adjustment of the klystron.
The negative voltage on the klystron repeller at manual frequency
control (Fig.72) is determined by the position4 of potentiometers R22-56
(REPELLER VOLTAGE) and R22-59 (ZONE SELECTION).
During AFC mode of operation the slider of potentiometer R22-56
(REPELLER VOLTAGE) is disconnected from the klystron repeller, and a plate
411 load circuit of the saw-tooth oscillator valve (V22-7) is connected to it.
In this case the voltage on the repeller is determined by the voltages of
potentiometer R22-59 (ZONE SELECTION) and the saw-tooth oscillator.
Presence of two potentiometers R22-56 (REPELLER VOLTAGE) and R22-59
(ZONE SELECTION) adjusting the voltage on the repeller makes it possible
to carry out initial tuning of the oscillator (at manual frequency control)
by means of both potentiometers so that during automatic frequency control
saw-tooth-voltage will be located symmetrically relative to the region of
the klystron frequency.
The unit supply circuits are energized by two switches W22-1 (HEATER)
and W22-2 (PLATE) situated on the front panel of the unit (10 and 119 Fig.65).
When turning on,switch W22-1 a neon lamp, +150 V (N22-13) comes on; when
.../turning on
SIM
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wmuJw..
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turning on switch W22-2 a neon lamp, +250 V (N22-15) cones on. Both lamps
are located on the front panel of the unit.
Intermediate-Frequency Preamplifier
The I.F. preamplifier serves to amplify the echo signal voltage. The
value of amplification is selected in such a way that loss in the long
junction cable through which the signal is conducted to the amplifier
oi the automatic tracking channel will not reduce the receiving system
sensitivity.
The input of the I.F. preamplifier is very close to the crystal mixer.
This excludes the possibility of appreciable weakening of the signal in
the junction cable between the mixer and I.F. preamplifier and consequently,
decrease of the signal-to-noise ratio at the input of the receiving system.
The I.F. preamplifier is comprised of three stages. The first two
stages utilize 6Z1P valves (V22-8, V22-9) in a circuit; earthed cathode-
earthed grid (Fig.65). The use of this circuit is due to the fact that it
has. a very low noise factor and gives relatively high amplification and
stability in operation.
The third stage (V22-10) employs a valve bf the 6Z4 type With an
oscillatory circuit placed in the plate circuit.
From the crystal mixer output the intermediate-frequency signal is
conducted through the cable to the input circuit of the first I.F.
preamplifier stage.
The two circuits of the first stage input circuit :4ise the output
admittance of the crystal mixer to a value ensuring optimum signal-to-noise
ratio on the grid of valve V22-8.
The primary circuit is formed by parallel-connected (for high-frequency)
inductors L22-6, L22-9 and the capacitance of the mixer and cable connector
coupling the input of the I.F. preamplifier to the mixer. Inductors
L22-6 and L22-9 are wound on resistor R22-27 and R22-30 which do not impair
.../the circuit
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Ara. mon .111
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- 88 -
the circuit quality factor noticeably, since the primary circuit quality
factor is low due, to shunting action of the crystal output resistance which
is rather small (approx. 300 ohms).
Connected in series with inductor L22-6 are inductors L22-7, 1.22-8
wound on resistor R22-28, R22-29. These inductors together with capacitors
C22-239 C22-24 constitute a radio-frequency filter in the crystal current
excuit.
To measure D.C. component of the crystal mixer current use is made of
411 milliammeter Pp22-1 placed in the current circuit between inductor L22-8
and earth. With switch W22-3 set in position AFC the instrument reads the
value of the A10 mixer current, whereas with the switch in position SIGNAL,
the value of the signal mixer current. The current value is determined
by the power conducted from the oscillator to the crystal.
Capacitor C22-25 separates the control grid circuit of the valve from
the D.C. circuit of the crystal mixer.
The primary circuit of the I.F. preamplifier input is tuned to resonate
with the intermediate frequency. The secondary circuit is formed by' the
input capacitance of valve V22-8 (6Z1P) and inductor L22-10; the load from
which the signal is applied to the valve grid is the input capacitance of
valve V22-8. The circuit is tuned to the intermediate frequency by
changing inductance of .coil L22-10 With the help of a brass ring which is
inserted into the coil. The ring is isolated from the chassis.
The plate load of the first stage valve (V22-8) is an oscillatory
circuit consisting of inductor L22,-11, the output capacitance of valve
V22-89 the input capacitance of valve V22-9 and the capacitance of the wiring.
Inductor L22-12 neutralizes plate - grid capacitance of valve V22-8
? thereby slightly improving the noise factor of the system and increasing
the stability of the first stage operation.
Inductor L22-12 and the plate - grid capacitance of valve V22-8
const,itute a parallel oscillatory circuit. The circuit is tuned to the
,
.../intermediate frequency
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tra ?73.253
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-89-
intermediate frequency by changing inductance of coil L22-12 with the
help of an insulated brass ring.
Resistor 1122-23 serves to obtain automatic bias on the grid of valve
122-9.
Capacitor C22-29 is a blocking type capacitor for intermediate frequency.
D.C. component of the plate current of the second stage valve V22-9 based
cn an earthed grid circuit passes through resistor R22-33 and inductors
L22-129 L22-109 L22-9. The plate load of the second stage is a circuit
formed by inductor L22-13, the output capacitance of valve V22-10 the input
capacitance of valve V22-99 and the capacitance of the wiring. The
circuit is tuned to the intermediate frequency by changing inductance of
coil L22-13 with the aid of a movable brass core.
Resistor R22-35 is leak for the control grid of valve V22-10. The
value of this resistor shunting the circuit determines in the main the pass
? band and amplification factor of the 1.F. preamplifier.
The I.F. voltage taken off the circuit is applied. through capacitor
C22-32 to the grid. of the third stage valve V22-10 (6Z4). The equivalent
circuit of the stage is presented in Fig.73.
The plate load. of the third. stage of the I.F. preamplifier is a
parallel oscillatory circuit formed by inductor L22-.149 the output
capacitance of valve V22-10 and. the capacitance of the wiring. Placed in
series with this circuit is resistor R22-38 whose value is equal to the
characteristic impedance of the cable connecting the output of the I.F.
preamplifier with the input of the automatic tracking channel amplifier.
To make the circuit tuning independent of the length of the cable
(its capacitance) and. to keep losses at minimum during signal transmission
the input resistance of the cable is made resistive. The cable is loaded
by resistor R1-1 (75 ohms), connected. at the input of the amplifier unit
of the automatic tracking channel, whose value is equal to the characteristic
impedance of the cable (cable, type RK-39 is used).
RFERFT .../At such
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-90-
At such a low input resistance of the junction cable it is bettor to
place this resistance in series with the circuit as at parallel connection
the circuit resistance proves to be inadmissibly reduced and the amplification
factor of the I.F. preamplifier output stage is low.
The I.F. preamplifier valves are supplied from the +150 V rectifier
located on the same chassis.
The rectifier is composed of valve V22-11 (504S) and transformer
Tr22-3 (Fig.64).
Choke D122-1 and capacitors C22-36, C22-37 constitute
a filter. Resistor R22-62 and capacitor C22-46 comprise an additional
filter in the circuit supplying the plates of the AFC channel valves. The
rectified voltage is stabilized by stabilovolt V22-12 (SG4S) with resistor
R22-40.
The stabilized voltage of +150 V is applied to the grids of the I.F.
preamplifier valves. The presence of the rectified voltage is checked by
means of indicating neon lamp MN-3 (V22-13) located on the front panel
(+150 V).
Automatic Frequency Control (AFC) Channel
When the station is functioning the magnetron and klystron frequencies
may largely vary due to changes in temperature, humidity, supply voltage,
antenna rotation and a number of other factors. In this case the difference
frequency deviates from the rated intermediate frequency and normal
reception may be disturbed.
The AFC channel provides such trimming of the oscillator frequency
at which the difference between the frequencies of the klystron and magnetron
is kept approximately equal to the rated intermediate frequency of the
receiving system.
The station employs an AFC search circuit. The AFC channel includes:
an AFC mixer, I.F. amplifier stages, a discriminator, a pulse amplifier and
a control circuit consisting of a saw-tooth oscillator (phantastron) and
a diode.
SERF
___/Tn thn
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?
-91 -
In the AFC channel, use is made of the signal directly furnished
from the transmitter to the receiver (main pulse).
The signal is conducted to the AFC mixer through the cut-off attenuator
of the waveguide type. The attenuator damping value is taken very large
so as to reduce the main pulse power applied to the crystal to 1 - 2 mV.
The microwave oscillator output is applied to the mixer through the
coaxial cable. After leaving the mixer the signal is conducted through
a section of the coaxial cable to the primary winding of input transformer
Tr22-1. Connected in series with the transformer primary winding is a
R.F. filter in the measuring circuit of the crystal current D.C. component.
The filter is formed by inductors L2271, L22-25 wound on resistors R22-2,
R22-3 and capacitors C22-1, C22-2.
The primary winding of transformer Tr22-1 with the capacitance of the
wiring, the capacitance of connectors and the capacitance of the junction
cable constitute a parallel oscillatory circuit tuned in, resonance with
the intermediate frequency of 30 Mc/sec.
When measuring D.C. component of the crystal mixer current (switch
W22-3 in position AFO)an instrument, type Pp22-1,. (CRYSTAL CURRENTS) is
placed in the current circuit between inductor L22-2 and earth. The
crystal current D.C. component is shorted through resistor R22761 (100 ohms)
equal to the internal resistance of the instrument.
The secondary winding of transformer Tr22-1 together with the input
capacitance of valve V22-1 and the capacitance of the wiring constitute an
oscillatory circuit tuned to the intermediate frequency by means of semi-
variable capacitor C22-3.
To widen the pass band the secondary winding of the transformer is
shunted by resistor R22-1 (300 ohms).
Transformer Tr22-1 is designed so that its primary winding may be moved
relative to the secondary winding. By moving the primary winding it is
.../possible to
SECPET
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umogiou...
-92--
possible to vary the winding coupling factor and consequently the amplification
factor of the AFC channel.
The use of a double input circuit with transformer coupling between
the circuits reduces the influence of variation of the crystal mixer out-
put resistance on the input of the first valve of the I.F. amplifier.
From this circuit the I.F. voltage is applied to the control grid of
valve V22-1 of the first stage. The first and second stages Of the I.F.
amplifier (V22-11 V22-2) are based on resonance amplifier circuits using
pentodes 6Z4 with oscillatory circuits in the plate circuits.
The oscillatory circuits are formed by inductors L22-3, L22-4, the
capacitance of the wiring, output and input capacitances of the valves.
The circuits are shunted by resistors R22-6 and R22-9 (510 ohms) which
determine the pass band and the amplification factor of the I.F. amplifier
channel.
Placed in the cathode circuit of the first stage valve (V22-1) is
variable resistor R22-63 equal to 1 kilohm. This resistor controls the
channel amplification at intermediate frequency, its slotted shaft is
brought out to chassis top and marked AFC AMPLIFIUTION. Resistor R22-63
is included in the circuit of a divider formed by resistors R22-63 and
R22-64.
Resistors R22-4, R22-7, R22-10 serve to develop automatic bias voltages
on the control grids of the valves of the first, second and third I.F.
amplifier stages due to the cathode current of the valves.
Connected into the plate circuit of the third stage valve (V22-3) is
the primary winding of the transformer (Tr22-2) circuit of the discriminator
(V22-4). The secondary winding of the transformer circuit is connected
(with its ends) to the plates of the valve (6H6S) of the discriminator
(Fig.74) producing output pulses whose polarity and value are determined by
the magnitude and sign of detuning of the intermediate frequency relative
.../to its
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?
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to its rated value. The discriminator differently reacts to the signals
whose frequencies are higher or lower than the rated.
The discriminator primary circuit is formed by capacitor 022-12, the
output capacitance of the valve, the capacitance of the wiring and the
primary winding of transformer Tr22-23 the secondary circuit - by capacitor
C22-14 and the secondary winding of transformer Tr22-2.
The primary and secondary circuits of the discriminator are tuned
?to the intermediate frequency of 30 Mc/sec. As the coupling between
the circuits is weak the resonant frequencies of the circuits are determined
in the main by their own parameters.
The quality factor of the primary circuit is low, therefore within a
certain range near the intermediate frequency, the dependence of voltage E1
across the circuit upon the frequency is negligible.
Voltage E across the secondary circuit is also relatively constant
in value within this frequency band and is in phase with El.
Current 12 is induced in the secondary oscillatory circuit which
develops a voltage across the secondary winding of transformer Tr22-2:
E2 I2XL '
2 -
where XL is inductive resistance of the secondary winding.
2
The value and phase of voltage E2 vary with the change of the
frequency, since the character of the, circuit impedance depends upon the
frequency.
Each diode of the discriminator valve is fed with A.C. voltage equal
to the geometrical sum of oscillatory voltage E1 across the primary circuit
and a half of voltage E2 developed across the coil of the secondary winding.
Vector diagrams of voltages in the discriminator circuits are shown in
Fig.74, where
E2
7 E1 . +--- and E4 El -
'3 2
STIET
.../The secondary
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?
?
?
The secondary circuit is tuned to the intermediate frequency of 30 Mc/sec,
therefore at the input voltage of a frequency of 30 Mc/sec equal to the
intermediate frequency voltages E3. and E4, as seen from the vector diagram,
are equal in phase, and consequently, currents across the detector load
(resistors R22-14 and R22-15) are equal in magnitude but opposite in
direction. In this case the resultant Voltage between point a and earth
equals zero.
When the intermediate frequency deviates to one or the other side from
the rated I.F. of 30 Mc/sec the phase shift between voltages El and E2
changes and voltages E3 and E4 will not be any longer equal in magnitude.
Currents flowing through resistors R22-14 and R22-15 will also be unequal
and the resultant voltage at the output of the discriminator detector
between point a and earth will not be equal to zero. Depending upon the
value and sign of detuning of the intermediate frequency relative to the
rated, this resultant voltage atthe discriminator detector output changes
its value and has either positive or negative sign (Fig.75). The
discriminator circuit is designed so that positive values of the output
voltage are obtained at lower frequencies than the rated intermediate
frequency of 30 Mc/sec, whereas negative values at frequencies higher than
the rated intermediate frequency of 30 Mc/sec.
Thus, with the I.F. pulse voltage applied to the input of the
discriminator, its output, depending upon the frequency of incoming signals,
-feeds out a train of positive or negative pulses of various amplitudes
(Fig.76).
Such a form of the discriminator pulse response ensures proper operation
of the AFC system only in ease the oscillator frequency fo is previously
set higher than frequenoy fm of the magnetron.
The functioning of the successive elements of the AFC system boils
down to the following 2 the voltage pulses from the discriminator obtained
.../due to
SEMI
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k..-;,16.unazzt.1
- 95
due to deviation of the intermediate frequency from the rated value I.F.
of 30 Mb/sec are amplified by a pulse amplifier (1J22-5) and act on the
control circuit, which produces a control- voltage changing the klystron
frequency. The control voltage changes the klystron frequency in such a way
that the rated intermediate frequency is attained at the mixer output.
The control circuit is comprised by a saw-tooth oscillator (V22-7)
and a diode (V22-6).
The saw-tooth oscillator employs pentode V22-7, type 6Z4, which when
no pulses are applied to its input from the pulse amplifier (V22-5)
functions as a self-excited oscillator (Fig.78).
Self-excitation of the saw-tooth oscillator is achieved due to
capacitor 022-22 connected into the circuit. The capacitor provides
coupling between the suppressor and screen grids. In the presence of such
coupling an increase in the screen grid current causes negative voltage to
111 appear on the suppressor grid and vice versa.
?
Discharge of capacitor 022-21 through valve V22-7 and a chain of
resistors R22-20 and R22-23 raises the voltage on the valve control grid.
This causes an increase in the plate current of this valve and a decrease
in the voltage on its plate. The plate voltage drop is conducted through
capacitor 022-21 to the control grid thereby slowing down the rise of the
grid voltage and consequently the rise of the valve plate current and the
voltage drop across the plate.
Any decrease of the discharge current results in a decrease of the
negative voltage between the control grid and the cathode, which opposes
the decrease of the discharge current.
Thus, due to strong feedback between the plate and the control grid
through capacitor 022721, the discharge current remains approximately
constant, the plate voltage changes almost linearly.
This process goes on until the, plate voltage drop reaches the value
at which redistribution of the valve cathode current between the screen
.../grid and
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grid and the plate takes place (Section b-c, Fig.77). The voltage on
the plate decreases to 15 - 20 V relative to the cathode. In this case
normal Current distribution between the plate and screen grid is disturbed
and the screen grid current begins to rise, and the grid potential - to fall.
A decrease of the voltage on the screen grid is conducted through
capacitor 022-22 to the suppressor grid which brings about a further
decrease of the plate current and an increase of the screen grid current
and consequently an increase of the negative potential on the suppressor
grid. This process is going on in an avalanche-like manner. As a
result the negative voltage on the screen grid reaches such a value that
the valve proves to be cut off for the plate current (point c, Fig.77).
The plate voltage rises, so does the voltage on the control grid, thereby
increasing the cathode and screen grid currents. In this case the
voltage on the suppressor grid is negative relative to the cathode; valve
V22-7 is completely cut off for the plate current, the voltage on the
control grid is positive in relation to the cathode.
From this moment on capacitor 022-21 is being charged from the power
supply through resistor R22-26 and grid - cathode section of the valve.
The variation of the charge rate of capacitor 022-21 is determined by the
values of resistor R22-26 and capacitor C22-21. The capacitor is being
charged to a value approximately equal to the power supply voltage (Section
c-d, Fig.77).
At the moment capacitor 022-21 starts to charge the control grid
potential sharply rises to +2 - +4 V (Section b-c9 Fig.77). Further rise
of the grid voltage is limited by grid currents.
Capacitor C22-22 begins to discharge through the screen grid - cathode
section and resistor R22-24.
As the capacitor discharges the negative
voltage on the suppressor grid decreases exponentially. The rate of
discharge is determined by values of resistor R22-24 and capacitor 022-22.
...At a
CRET
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aulaLl
97 ?
?
?
?
At a cortain moment the voltage on the suppressor grid reaches the potential
and takes the valve from the cut-off condition for the plate current
(point d, Fig.77). The capacitance value of capacitor 022-22 is selected
large enough so that the potential on the suppressor grid will not be able
to recover until capacitor 022-21 is not charged to the voltage of the
power supply and the voltage on the plate approximates that of the power
supply E.
At the instant the valve becomes conducting for the plate current,
the plate potential suddenly decreeses by a value determined by product
IaRa (Section d-e, Fig.77).
This sudden decrease of the plate voltage is
conducted to the control grid through capacitor 022-21, which causes a
decrease of the screen grid current, an increase of the voltage on the
screen and suppressor grids and further rise of the plate current. This
process is also going on in an avalanche-like manner, which results in the
voltage being sharply raised on the screen and suppressor grids. The
plate voltage decreases, so does the voltage on the control grid and at
this moment it becomes almost equal to the cut-off potential for the plate
current.
Capacitor 022-21 begins to discharge through the valve and resistors
R22-20 and R22-23. As the capacitor discharges the potential on the
control grid rises. The plate voltage decreases linearly and the entire
process is being repeated.
Thus the saw-tooth oscillator produces saw-tooth voltage of about
3 to 5 c.p.s. (Fig.70, c) which is applied to the klystron repeller.
The klystron frequency, as was mentioned before, is set (during manual
frequency control) higher than that of the magnetron frequency by the value
of the intermediate frequency of 30 Mc/sec. With the saw-tooth variation
of the oscillator voltage at the initial moment the negative voltage
applied to the klystron repeller is small and therefore, the difference
.../frequency fo fm
SEcRET
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alrelLu
98 -
frequency fo fm is less than the rated intermediate frequency (Fig.70, a).
There are no pulses at the amplifier output. The saw-tooth oscillator
searches for. frequency.
As the negative voltage rises on the repeller, the oscillator frequency
increases and the difference frequency enters the pass band of the I.F.
amplifier of the AFC channel (Fig.70, e)
With the transmitter switched on, the pulse amplifier (in accordance
with the discriminator response curve) produces first negative pulses to
which the saw-tooth oscillator cireuit does not respond (Fig.705 f).
The negative voltage on the repeller continues to rise and consequently
the oscillatol frequency increases. The difference frequency increases as
well and passes zero point of the discriminator response curve (Fig.70, f)
which is being set at the resonance frequency of the I.F. amplifier channels
of the receiving system (30 Mc/sec).
The pulse amplifier (V22-5) produces positive pulses (Fig.77). They
charge capacitor C22-20 through the control diode (V22-6).
When capacitor C22-20 discharges through resistor R22-20 during the
pulse interval, a negative voltage (relative to the cathode of valve V22-7)
is developed across this resistor. The voltage rises with an increase in
the amplitude of the pulses applied to capacitor C22-20. At an instant
when voltages across resistor R22-20 and the control grid of valve V22-7
become equal, the discharge current of capacitor C22-21 flowing through
resistor R22-23 ceases, i.e. saw-tooth variation of the plate current
ceases and the voltage that was present at the moment the saw-tooth voltage
oscillations were stopped, is set up on the plate of oscillator V22-7.
Due to a large amplification factor of the AFC channel the saw-tooth
voltage oscillations are stoped at inconsiderable deviation from the
frequency corresponding to zero point on the discriminator response curve
(0.2 to 0.3 Mc/s). At the moment of stopping the klystron frequency
.../ceases to
SECRET
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?
?
-99-
ceases to change (Fig.70, g). In this case an average voltage is impressed
on the control grid of valve V22-7. The voltage maintains the oscillator
frequency at such a level which ensures that the intermediate frequency
equals the rated value.
From this moment the saw-tooth oscillator functions as a D.C. amplifier,
i.e. ?the valve plate voltage follows the control grid voltage and automatically
maintains the difference of the magnetron and oscillator frequencies equal
to the intermediate frequency of the receiving system.
If the difference frequency exceeds the intermediate frequency of
30 Mc/sec positive pulses will be increased at the pulse amplifier output,
which will result in an increase of the negative voltage on the grid of
valve V22-7 and in an increase of the plate voltage. Therefore, the
negative voltage on the klystron repeller_will decrease and the klystron
will generate lower frequency at which the difference frequency equals the
intermediate one of 30 Yb/sec.
If the difference frequency decreases, positive pulses at the pulse
amplifier output, while decreasing, will be cancelled out; capacitor
C22-21 begins to discharge and the plate voltage decreases according to a
saw-tooth law until positive pulses interrupting this changeappear at the
pulse amplifier output.
' If the oscillator frequency, at the given polarity of the discriminator
response curve, is set below the magnetron frequency, the search circuit
will carry out tuning on a false point and keep the difference frequency
unequal to the intermediate one of 30 Mc/sec, which will result in sharp
reduction of the receiver sensitivity.
Diagram 78 illustrates the functioning of the AFC circuit when the
oscillator is tuned to frequencies higher or lower than magnetron frequencies.
Curves 1 and 2 show the relation of the voltage at the AFC circuit output
(plate voltage of oscillator valve V22-7) to the oscillator .(heterodyne)
Sag
./frequency. Curves
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rpjoig
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frequency. Curves 3 and 4 show the relation of the oscillator frequency
to the voltage on the klystron repeller during searching.
When the oscillator tuning frequency is lower than magnetron frequency,
positive pulses at the output of the AFC channel, stopping the saw-tooth
voltage of oscillator V22-71 appear at the difference voltage (of the
magnetron and klystron) exceeding the rated intermediate frequency and the
AFC circuit maintains the frequency other than the intermediate one
(point B1). Near point B2 the circuit operation is unstable and any
change in the klystron frequency detunes automatic frequency control. In
point A the circuit function is stable.
The saw-tooth oscillator is supplied from two rectifiers (-250 and
-255 V), located on the chassis of the I.F. preamplifier unit. These
rectifiers are based on two kenotrons 504S (V22-14 and V22-19) and are
used to supply the klystron and the saw-tooth oscillator.
411 The rectified voltage of -250 V is stabilized by the electronic
?
regulator employing valves V22-16 and V22-18 whose operation has been
analysed in detail in Section 3.
The rectified voltage of -255 V is stabilized by a series combination
of stabilovolts SG3S and SG4S (V22-20 and V22-21).
When placing switch W22-4 in position AFC the voltage of -250 V is
applied to the plate of valve V22-7.
Pin 2 of valve V22-21 is negative potential applied from the series
combination of the rectifiers (-250 and -255 V), i.e. -505 V. This voltage'
is applied to the cathode of valve V22-7. Thus, a voltage of +250 V is
applied between the plate and cathode of valve V22-7.
5. AUTOMATIC TRACKING CHANNEL AMPLIFIER
The automatic tracking channel amplifier unit (Figs 79, 80) is located
in the upper left-hand part of the main control board cabinet.
A key diagram of the amplifier unit is presented in Fig.81 .(See Album).
SEPRET .../The automatic
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- 101 -
The automatic tracking channel amplifier is designed for amplification
411 of signals coming from the I.F. preamplifier. It is provided with two
amplifier channels: a range channel and an automatic tracking channel.
The signal from the output of the I.F. preamplifier (connector Zw22-6) is
furnished through the coaxial cable with a characteristic impedance of
75 ohms to the input of the automatic tracking channel amplifier (connector
Zw1-1) and then through coupling capacitor C1-1 to the control grid of
valve V1-1.
? Resistor R1-1 (75 ohms) as was mentioned above serves to match the
input resistance of the first valve of the automatic tracking channel
amplifier with the characteristic impedance of the cable.
The input circuit of the first stage of the automatic tracking channel
'amplifier is formed by inductor L1-1 together with the input capacitance
?of valve V1-1 (6Z4) and the capacitance of the wiring. The circuit is
shunted by small resistance of R1-1 due to which it has a wider pass band
as compared with the circuits of the successive stages, where the resistors
shunting the circuits have considerably greater values (470 to 1000 ohms).
The first, second, third and fourth stages of the automatic tracking
channel amplifier (V1-1, V2-2, V1-3 and V1-4) are the fourth, fifth, sixth
and seventh stages of the I.F. amplifier in the receiving system respectively.
The I.F. amplifier stages in the unit are based on resonant amplifier
circuits with parallel plate supply, using pentodes 6Z4, having oscillatory
circuits in the control grid circuits.
In addition to inductors L1-1, L1-29 etc.' the oscillatory circuits
include interelectrode capacitances of the valves (C
input + Coutput)' the
wiring capacitances (Cm) and inductor self-capacitances (Cd). The total
capacitance of the circuit is approximately 20 pF.
The control grids of the first two valves are fed with the negative
voltage from the automatic gain control (AGC) circuit.
1TRET
.../Resistors R1-49
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War.
- 102 -
Resistors R1-4, R1-79 R1-119 R1-14, R1-199 R1-23 (Fig.81) that are the
? plate loads of the valves, are used to shunt the circuits and to determine
the amplification factor and pass band both for the range channel and
automatic tracking channel.
The circuits are tuned ,to the intermediate frequency by changing
inductance,of the coils with the help of movable brass cores. The initial
Vas on the valves of the I.F. amplifier stages of the automatic tracking
channel amplifier unit is caused by the valve current flowing through
1111 resistors R1-39 R1-8, R1-109 R1-15, R1-22.
After the fourth I.F. amplifier stage of the automatic tracking channel
amplifier unit the receiver amplifier channel is separated into twos the
automatic tracking channel amplifier and range channel amplifier.
The automatic tracking channel amplifier is comprised of two I.F.
amplifier stages (V1-5 and V1-6), a detector (left-hand diode of valve
V1-7) and two video amplifier stages (V1-3 and V1-8).
The output voltage from the fourth I.F. amplifier stage (V1-4 of
the unit is applied to the input of the fifth stage (V1-5). The fifth
stage is usually cut off and is made conducting only when the screen grid
of valve (V1-5) is supplied with the very narrow gate of 0.3 microsec.
duration and 100 - 120-volt amplitude. The gate is furnished from the
range and very narrow gate indicator unit through the cable via connector
W11-5. When no very narrow-gate is applied valve V1-5 is cut off by
the negative voltage on the screen grid (about -100 V) taken from the
voltage divider formed by resistors R1-609 R1-61 in the circuit of the
-150-volt rectifier.
Therefore, the grid of the next sixth stage (V1-6) is supplied only
with the voltage of the reflected signal that is timed with the very
narrow gate.
The moment of feeding the voltage ,of the very narrow gate to the
screen grid of valve V1-5 is set by the range operator who by operating
.../the handwheel
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ersquir
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the handwheel aligns electronic markers on the fine range tube with the
signal reflected from the selected target thereby timing the voltage of
the very narrow gate pulse with the reflected signal.
During automatic tracking of the selected target this alignment is
done automatically by the follow-up system of the automatic range tracking.
Thus, only signals reflected from the target selected by the operator
are amplified in the amplifier of the receiver automatic tracking channel.
Placed in the control ,grid circuit of valve V1-5 is resistor R1-17 to
reduce the undesirable effect (caused by triggering and cutting off of the
automatic tracking channel) on the parameterc (amplification factor, pass
band and resonance frequency) of the range channel I.F. amplifier.
- The cathode circuit of valve V1-5 contains variable resistor R1-21
used for regulation of the automatic tracking channel I.F. amplifier.
The resistor slotted shaft is brought out to the front panel of the unit
111 and is marked AUTOMATIC SENSITIVITY CONTROL.
To extend amplification control range the cathode of valve V1-5 is
supplied with additional bias from the divider formed by resistors R1-57
1111 and R1-21 to which a stabilized voltage of +120 V is applied.
When AGO is functioning the resistance value of resistor R1-21 affects
the amplification factor of the range channel. Should the resistance
value, say, of R1-21 be increased the amplification factor of the automatic
tracking channel will decrease. This will cause a decrease of the negative
bias applied to the first and second I.F. amplifier stages from the AGC
stage, and an increase of the amplification factor for these stages and,
.consequently, the amplification factor for the range channel, as the first
and.second I.F. amplifier stages of the automatic tracking channel amplifier
unit are common for both channels of the receiving system.
When tuning the automatic tracking channel at the manufacturing plant
or repair workshop, the screen grid of valve V1-5 is fed with a D.C.
?"voltage
SECRET
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COLUAILI
_ 104--
voltage of +120 V. For this purpose jumper W1-3 is set in position-
111 +120 V. In position STROBE jumper W1-3 connects jack G1-3 with G1-4 and
the very narrow gate is applied from the range indicator unit to the screen
grid of valve V1-5. Total amplification of the intermediate frequency
amplifier, from the input of the amplifier to the output of the ninth
stage of the intermediate frequency amplifier of the automatic tracking
channel, is about 200,000. The voltage from the ninth I.F. amplifier stage
is applied to the second detector (valve V1-7) employing (to reduce the
detector capacitance) one half of the double diode 6H6S; the other half
of the valve is earthed. The detector load is resistor R1-26. Capacitor
01-32 and inductor L1-8 constitute a filter smoothing intermediate frequency
ripples across the load resistor.
To monitor the operation of I.F. amplifier of the receiver automatic
tracking channel during the receiver tuning, a microammeter may be connected
into the D.C. component circuit of the detector current. For this purpose
monitoring jack G1-1 (DIODE CURRKN'T) is provided whose contacts are
connected to each other with the plug connector removed. The microammeter
is shunted by resistor R1-28 (220 ohms) whose main function is to prevent
discontinuity of the D.C. component circuit of the detector at the moment
the contacts, of jack G1-1 are opened.
The negative voltage pulses from the detector load are furnished to
the input of the first stage of the video amplifier (V1-8). Both video
amplifier stages operate as resistor-coupled amplifiers. . The plate load
of the first stage is resistor R1-309 the plateload of the second stage is
resistor R1-35.
To correct the video amplifier frequency characteristic in the high-
?
frequenCy-region, chckes,...L1-9-and7-171=11??paced
the first andAecond stages of ier. The choke resistance
?
7? qc
rises as the_frequericy increabee, thustaibing the total resistance of the
in the plate circuit of
plate load. This results in compensation of the resistance drop across
_ ? .-f-CREI .../the load
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ehrrecarv
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- 105 -
?
?
the load caused by spurious capacitances. The use of correcting chokes
at high frequencies extends the band of amplified frequencies which is
necessary for undistorted amplification of short pulses applied to the
1;ideo amplifier from the detector (Fig.83).
The negative voltage pulses are furnished from the plate of valve
V1-9 through coupling capacitor C1-41 and resistor R1-37 to the cathode
.of the AGC detector (the left-hand triode of valve 6N8S), while through
capacitor 01-40 - to connector W1-31 from where they are conducted to the
automatic tracking and automatic range finder units.
One LP% amplifier stage of the range unit (V1-11) located in the
automatic tracking channel amplifier unit employs a valve of the 6Z4 type.
The circuit of the stage is similar to that of the I.F. preamplifier, but
the valve grid circuit contains an oscillatory circuit common with the
fifth I.F. amplifier stage of the automatic tracking channel. The output
voltage of this stage is applied to the range channel amplifier through
connector W1-4.
Besides the described amplification channel the unit accommodates the
AGC circuit (V1-10) and a rectifier with a +120-volt voltage stabilizer
(V1-12, V1-13 and V1-14, V1-15).
Gain Control
The receiving system provides for manual and automatic gain control.
The automatic gain control, during automatic target tracking, provides
the operation of the automatic tracking channel in the linear section of
the receiving system amplitude characteristic. In this case the signal
modulated by the error signal voltage is normally conducted through the
receiving channel.
If the signal reflected from the target being tracked is excessively
increased, the AGC circuit automatically reduces the amplification factor
of the first and second I.F. amplifier stages of the automatic tracking
.../channel amplifier
.cFPUT
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?
?
?
?
-106-
channel amplifier unit due to the additional negative bias voltage applied
to the valve grids of these stages.
During automatic tracking of the target in angular coordinates the
receiving system gain is controlled only automatically. In other modes of
operation manual control is used. The AGC circuit consists of a detector
the left-hand triode of valve V1-10 (6N8S) connected as a diode, and a D.C.
amplifier with a cathode load employing the right-hand triode of the same
valve. The triode grid is connected to the middle contact of relay P1-1.
When setting selector switch (W12-1) (MODE OF OPERATION) located in
the antenna control unit in position (AUTOMATIC) the winding of relay
P1-1 is supplied with A.C. voltage (110 V, 50 c.p.s.), contacts 5-6 of
the relay close and the grid of the AGC amplifier is supplied with voltage
from the load of the AGC detector (divider R1-46, R1-45, R1-42). In this
case the receiver operates with AGC (Fig.84).
The cathode of the left-hand triode of valve V1-10 (AGC detector)
is supplied with a Positive D.C. voltage of +30 V from divider R1-39,
R1-40, fed with a stabilized voltage of +120 V.
In the absence of the signal from the output of the receiver automatic
tracking channel, the detector plate is under a small negative (in relation
to earth) potential (approximately' -2 V) taken from the voltage divider
composed of resistors R1-43, R1-44, R1-42 (in the automatic tracking channel)
and R7-99 (in the automatic range finder unit) fed by a stabilized voltage
-105 V. Therefore, the AGC detector is cut off by a negative voltage of
about 32 V. In this case there is no voltage drop across the load
(R1-45, R1-46) of the detector and, consequently, the grid potential of the
D.C. amplifier (the right-hand triode of valve V1-10) is approximately -2 V.
The AGC amplifier is connected as a cathode-loaded stage (R1-41). The
plate voltage of this stage is attained by adding stabilized voltages of
+120 and -105 V and makes up about 225 V.
SEMI
.../The resistance
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Ktrvevctry
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- 107 -
The resistance value of resistor R1-41 should ensure a voltage drop of
? 105 V across the resistor during the plate current flow through the valve
(at the grid potential of about -2 V). In this case the AGC resultant
voltage on the grids of the first and second stages of the I.F. amplifier
equals zero, while the bias voltage of these stages is determined by the
voltage drop across the resistors in the circuits of the valve cathodes.
The receiving system provides maxitum gain.
The initial zero voltage is set on the grids of the first and second
I.F. amplifier stages with the help of potentiometer R1-42 whose slotted
shaft is brought out to the unit chassis and marked AGC SETTING.
If the amplitude of the negative pulses at the output of the receiving
system automatic tracking channel exceeds 32 V the AGC detector is triggered
by the pulses. Capacitor 01-44 is being charged through the diode and
resistor R1-37. In pulse intervals capacitor 01-44 is being discharged
through the detector load resistor R1-46, R1-45, R1-42. The time constant
of the capacitor charging circuit makes up 5 microseconds which exceeds
the duration of the output pulse (of the receiving system automatic tracking
channel) equal to 0.3 microseconds.
The time constant of the capacitor discharging circuit makes up
6200 microseconds, which considerably exceedsthe duration of pulse intervals
which are approximately 533 microseconds. As a result the voltage across
capacitor 01-44 under steady conditions remains almost constant slightly
changing by the action of pulses at the receiver output.
The more the pulse amplitude at the output of the receiving system the
greater the value of the voltage across capacitor 01-44.
The voltage across capacitor 01-44 is set (when the amplitude of
pulses at the receiving system output is invariable) at such a level at
which the electricity obtained by the capacitor for a period of the pulse
travel through the charging circuit, equals the electricity lost by the
capacitor in the discharging circuit during the pulse interval.
erpprii .../The voltage
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rEn, rse "MI
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%Id:4.AV El LES= LI
- 108 -
The voltage caused by discharge of capacitor 01-44 is taken from
? resistor R1-45 to the grid (4) of the right-hand triode of.valve V1-10
(AGO amplifier). Thus, if capacitor 01-44 proves to be charged due to
the AGC detector operation, to a voltage exceeding the voltage drop across
resistor R1-42, approximately one quarter of this additional negative
voltage is conducted to the grid (4) of the D.C. amplifier. The valve
plate current decreases. The voltage drop across resistor R1-41 becomes
less than 105 V and the valve cathode potential drops below zero. This
negative voltage is applied to the valve grids of the first and second
I.F. amplifier stages of the automatic tracking channel amplifier unit
and causes a reduction of amplification factors of these stages and
consequently of the entire receiving system.
Thus, as the amplitude of echo signals increases the AGC system
automatically reduces the amplification factor of the receiving system and
protects separate stages from overloads.
Connected to the input of the right-hand triode of valve V1-10
?
(AGO amplifier) is capacitor 01-45.
The time constant of the charging
and discharging circuits of capacitor 01-45 through resistors R1-461 R1-45,
amounts to several seconds. As a result at rapid changes of the pulse
amplitude at the output of the receiving system automatic tracking channel
the voltage on the grid of valve V1-10 and consequently the output voltage
of the automatic gain control remain practioally constant, because these
voltages depend on the average level of the signal at the output of the
receiving system.
In particular, due to application of capacitor C17-45, the AGC system
does not react on ripples of the echo pulse amplitude with a frequency of
24 c.p.s. caused by deviation of the antenna axis from the target direction
and thus does not reduce the error voltage used for the antenna automatic
control.-
S CRET
...Manual gain
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ev,
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-109-
Manual gain control'. With selector switch W12-1 MODE OF OPERATION in
? position MANUAL the relay winding is de-energized, contacts 6-7 of relay
?
?
?
P1,1 (Fig.84) close and the grid of the D.C. amplifier is fed with the
voltage from a series combination of potentiometers R1-44 and R7-99, whose
knobs are brought out to the front panel of the amplifier units of the
automatic tracking channel and automatic range finder and marked GAIN
(R1-:44 and R7-99).
In this case the AGC detector is switched off and gain is controlled
manually.
By rotating knobs of potentiometers R1-44, R7-99 it is possible to
change the voltage on the grid of the right-hand half of valve V1-10
(AGO amplifier) and consequently the output voltage taken from the cathode
and the bias voltage on the valve control grids of the two first stages of
the automatic tracking channel amplifier,unit.
When turning knobs R7-99 and R1-44 to their extreme clockwise positions
the voltage on the grid of the right-hand half of valve V1-10 (AGC amplifier)
relative to earth will be equal to the voltage drop aCross resistor R1-42
(-1.5 to -2 V), i.e. will be the same as that during automatic gain control
with the AGO detector cut off.
In this case the circuit output voltage, i.e. the voltage between the
cathode of the AGO amplifier and earth, equals zero and the receiving
system operates with maximum amplification factor.
When rotating knobs GAIN (R1-44) and GAIN (R7-99) counter-clockwise
the grid.potential of the D.C. amplifier decreases and consequently the
circuit voltage becomes negative which results in decrease of the receiver
amplification factor.
Voltage Stabilizer
For stable operation of the receiving system the plate circuits and
screen grids of the I.F. amplifier stages of the automatic tracking channel
SECRET
.../amplifier unit
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WEAPAL
- 110 -
?
amplifier unit are supplied from the voltage stabilizer mounted on the
chassis of the automatic tracking channel amplifier unit.
Stabilization of voltage in the given circuits protects the operation of
the receiving system from the oscillations of the mains primary voltage and
change of the load current.
The input of the voltage stabilizer, composed of regulating valve
V1-13 (GU-50) and control valve V1-14 (6P9) is supplied with a voltage of
about 360 V from the reotifier output (Fig.81, See Album).
The stabilized voltage is regulated by changing the resistance value
of resistor R1-54 with the help of slotted shaft +120 V brought out to the
chassis; the slotted shaft is set so that the voltage at the stabilizer
output is equal !,,,UO +120 V.
The operating principle of the stabilizer is described above (See
Section 4).
The presence of the rectified voltage is checked with the aid of the neon
lamp N1-17 (+120 V) located on the front panel of the assembly.
6. RANGE CHANNEL AMPLIFIER
The range channel amplifier unit (Figs 85, 86) is located in the left
upper corner of the main control board cabinet under the amplifier unit of
the automatic tracking channel.
The range channel amplifier unit is designed for additional amplification
of signals to a value ensuring the normal operation of the range indicator
unit, plan-position indicator unit and automatic range finder.
The range channel amplifier unit (Fig.87, See Album) consists of one
I.F. amplifier stage, a detector and three video amplifier stages. The
unit chassis carries +300-volt and -150-volt rectifiers as well.
? The input of the range channel amplifier unit is fed with I.F. voltage
from the output of the eighth I.F. amplifier stage of the range channel
(V1-11) located in the automatic tracking channel amplifier unit. The
first I.F. amplifier stage of the unit is based on a resonant amplifier
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?
?
?
with an oscillatory circuit in the grid circuit. The cathode circuit of
valve V2-1 includes variable resistor R2-3 by means of which the range
channel amplification is regulated.
Resistor R2-3 is part of the divider in the circuit of the rectifier
voltage of +300 V. The slider shaft of the resistor is brought out to
the unit front panel and marked NOISE LEVEL SETTING, Resistor R2-1 is
the load of the output cable and its value equals the cable characteristic
impedance. The application of this resistor is similar to that of
resistor R1-1 of the automatic tracking channel amplifier unit.
The signal voltage amplified by an I.F. amplifier stage (V2-1) is
applied to the detector, i.e. to the right-hand diode of valve V2-2 (6H6S).
The overall intermediate frequency amplification of the range circuit
(from the input of the intermediate frequency pre-amplifier to the tenth
stage of the range channel intermediate frequency amplifier), is about 75,000.
The load of detector V2-2 is resistor R2-7. Choke L2-3 and capacitor
C2-7 constitute an intermediate frequency filter which prevents penetration
of I.F. voltage to the video amplifier input.
The first and second stages of the video amplifier (V2-3 and V2-4)
employ valves of the 6Z4 type connected as triodes, which ensures uniform
amplitude characteristic.
The grid of the first video amplifier stage (V2-3) is fed with positive
pulses from resistor R2-7. Therefore, the initial negative bias from
divider R2-9, R2-10, connected into the -105-volt rectifier, is applied
to the control grid of this valve to cancel out amplitude distortions
caused by grid currents.
For high-frequency compensation the plate circuit of the first stage
contains choke L2-4 connected in series with resistor R2-12.
The negative pulse is applied to the grid of valve V2-4 and because
of this it is not supplied with additional negative bias.
?"Resistor R2-17
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0116/ilhaCti;1213Daa 11
?
- 112
Resistor R2-17 and capacitor 02-11 are correcting elements improving
frequency characteristic of the stage and, consequently, of the entire
video amplifier. In the low-frequency region the capacitive reactance of
capacitor C2-11 becomes greater than resistance value of R2-17. As a
result the negative feedback reduces amplification of the stage in the
low-frequency region, which is equivalent to the high-frequency rise. The
stage operates without the initial negative bias, therefore, the bias on
the valve grid is determined by an average noise level. Should the noise
arise the operating point of the stage characteristic is shifted to the
right due to appearance of additional bias voltage caused by the grid current
across resistor R2-16 whose value is approximately 470 kilohms. In this
case the amplification factor of the stage decreases and the previous noise
level is preserved on the tubes. Thus, approximately constant noise, level
is kept on the tube screens, which facilitates observation of weak signals.
The plate load of the second video amplifier stage is resistor R2-15.
Resistors R2-39, R2-14 and capacitor 02-12 constitute a decoupling filter
in the supply circuit.
The third stage employs valve 6P3S (V2-5). The bias to its control
grid is fed by the -105-volt rectifier from divider R2-19, R2-20. The
plate load consists of resistors R2-26, R2-25, R2-24) R2-23, R2-21 and
R2-22 whose total resistance value is 1.5 kilohms. The negative voltage
pulses of 120 V amplitude are conducted to the range indicator unit
(to connector Zw3-4) from the plate load of this stage through connector
Zw2-3.
From connector Zw2-2 the positive pulses are furnished to the range
finder unit (to connector Zw7-4). In this case the pulses are taken from
resistor R2-30 in the valve cathode circuit.
The plan-position indicator is supplied with the output voltage through
the divider (resistors R2-28, R2-29). The negative pulses of 12 V amplitude
.../taken from
f7PFT
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au9KLI
_ 113 _
?
?
?
?
taken from the part of the divider (R2-29) are applied to the plan-position
indicator through connector Zw2-4. '(pin 5)i
The +300-volt rectifier employs two: kenotrons of the 5C4S type (V2-7
and V2-3). Capacitors C2-20, C2-19 and choke D12-1 constitute .a mid-shunt
filter in the rectifier circuit. Connected in series with the choke are
two wire-wound resistors R2-33 and R2-34, one of them being connected as a
potentiometer and serves to regulate the rectifier output voltage during
the unit tuning.
The -105-volt rectifier utilizes kenotron of the 5C43 (V2-9). The
voltage of -105 V is stabilized by stabilovolt SG3S (V2-10).
The neon lamps N2-11 and N2-12 serve for checking the +300 V and the
-105 V rectified voltages. They are located on the front panel of the
assembly (Fig.85).
Chapter5
RANGE MEASURING SYSTEM
1. GENERAL
The range measuring system is designed to measure the target range
continuously and accurately in the manual or automatio range tracking mode
of operation and. to synchronize the operation of the transmitter, receiver
and the plan-position indicator system.
The range measuring system (Fig.88) consists of the following components:
a range unit, a range and very narrow gate indicator, a range mechanism and
an automatic range finder.
The range measuring system is fed from the power pack of the range
measuring system and plan-position indicator and from the power pack of the
range measuring system.
The range unit synchronizes the operation of the transmitter, the
receiver, the range and very narrow gate indicator unit, the automatic range
SECRET
.../finder and
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OLL a
? 114 ?
?
?
?
.4106.
finder and the, plan-position indicator unit. For this purpose the range
unit generates sweep voltages .for the fine and coarse range tubes, trigger
pulses to trigger the transmitter and start the plan-position indicator
sweeps, voltage pulses to brighten the sweeps of the coarse range tube,
pulses to form the plan-position indicator range markers, pulses gating
the sweep trace on the fine range tube and the plan-position indicator tube
and forming the electronic marker on the coarse range tube.
The range and very narrow gate indicator is designed for visual
observation of the signals reflected from the targets. Besides, the unit
accommodates the final stages of the very narrow gate forming circuit. The
very narrow gate makes the receiver automatic tracking channel conducting
and triggers the gate forming circuit in the automatic range finder unit
and the circuit for forming an electronic marker on the fine range tube.
Short very narrow gate .oulses, making the receiver automatic tracking
channel conducting at the instant the signal reflected from the selected
target arrives, makes possible the tracking of the selected target
automatically in angular coordinates despite the presence of other targets
located at various ranges in the zone of the antenna beam coverage.
The range mechanism unit is designed for mechanical control of the
devices for tracking the target in range (the phase shifter and strobe
decade potentiometer) with range data transmission by means of the coarse
and fine selsyns.
The unit incorporates the stages of the very narrow gate forming circuit.
When rotating the range knob the phase of the voltage, forming the very
narrow gate, reverses relative to the phase of the crystal generator voltage,
which alters the start of the very narrow gate and the position of the fine
range tube electronic marker relative to the range zero mark.
The automatic range finder unit provides continuous tracking of the
target in range. For this purpose the unit produces a 50 c.p.s. control
.../voltage which
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aLUIPiLl
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?
voltage which is applied to the automatic tracking motor in the range
mechanism unit.
The value and phase of the control voltage are such that the automatic
tracking motor (rotating the shaft of the range mechanism and the shaft of
the phase shifter) ensures continuous alignment of the electronic marker
with the signal from the target being tracked.
2. OPERATING PRniCIPLE OF RANGE
MEASURING SYSTEM
A functional diagram of the range measuring system is presented in
Fig. 89.
Formation of Sweeps on Fine and Coarse Ran,ge Indicators
Circular sweeps on the fine and coarse range indicators are formed
When the electron flow is acted upon by sine-Wave voltages equal in
amplitude and shifted in phase by 900. The indicator Sensitivity for
horizontal and vertical deflecting plates to which sweep voltages shifted
in phase are applie, is different, therefore in practice the amplitudes of
the given voltages are also different.
The voltage applied to the vertical deflecting plates of the indicator
(Fig.90) causes the indicator electron beam and, consequently, the bright
spot on the screen to deflect up and down from the centre by a value
proportional to the instantaneous value of the voltage.
The voltage applied to the horizontal deflecting plates of the
indicater deflects the bright spot to the left and right from the centre.
During simultaneous action of two voltages applied to the indicator
deflecting plates the bright spot moves both in horizontal and vertical
planes successively passing points 0, 1, 2, 3, etc. on the screen, i.e.
moves in a circumference.
The time of one revolution of the bright spot equals the cycle of the
sweep voltage applied to the plates.
gFrIrr
.../To obtain
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?
?
?
To obtain the circular sweep on the fine range indicator the range unit
and the range indicator unit oroduce two sine-wave voltages of 74.955 Kc/s,
shifted in phase by 900
.
The voltage of 74.955 Kc/s (approximately 75 Ws) is produced by the
crystal-controlled oscillator. The oscillation frequency of the crystal
oscillator is somewhat lower than 75 Kc/s, because the propagation velocity
of radio waves is not 300,000 km/sec. but a bit lower than this value.
The oscillator voltage period, which is a precise time reference,
makes up 13.3 microsec. and equals the time required for the electromagnetic
siganl to make a round trip between the transmitter and the target that are
two kilometres apart. Therefore, the length of the sweep circumference of
the fine range indicator corresponds to the range of 2 km.
To create a circular sweep on the coarse range indicator two sine-wave
voltages of 3.75 Kc/s are required. The frequency of these voltages is
20 times as small as that of the crystal oscillator and consequently the
time during which the sweep describes a circle on the screen of the coarse
range indicator corresponds to the range of 40
The crystal crystal oscillator voltage is applied to the frequency division
circuit which generates voltages 5, 20 and 40 times lower than the frequency
of the crystal oscillator, i.e. approximately 15, 3.75 and 1.875 Kc/s. The
frequency is divided by multivibrators.
The first multivibrator is synchronized by the voltage of the crystal
oscillator. This voltage is previously converted into a pulse voltage of
the same frequency in the trigger pulse oscillator stage. The circuit is
designed in such a way that the first multivibrator, which will be henceforth
referred to as multivibrator 15 Kc/s, generates a pulse voltage whose
frequency is five times as low as that of the crystal oscillator.
The voltage of multivibrator 15 Kc/s synchronizes in turn the next
multivibrator that divides frequency by four. Thus the voltage of the
.../second multivibrator
FDFCREr
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?
second multivibrator has a frequency 20 times as low as that of the crystal
oscillator, i.e. 3,748 Kc/s. This multivibrator is called multivibrator
3.75 Ws.
The output voltage of multivibrator 3.75 Kc/s of approximately Square-
wave form is applied to the resonance amplifier whose load is a phase
shifting transformer. This transformer produces two voltages of 3.75 Kc/s
eqUal in amplitude and 90? out Of phase in relation to each other. These
voltages are applied through resonance transformer to two pairs of
deflecting plates of the coarse range indicator. The form of output
voltages of resonance transformers approaches the sine-wave form and therefore,
creates a circular sweep on the indicator screen; the duration of one
sweep revolution corresponds to one period of the sine-wave voltage and
equals 266 microsec.
The signals reflected from the target are furnished from the output
of the receiver range channel amplifier to central deflecting electrode of
both range indicators and form radial pips on the sweeps, i.e. target
markers.
Trigger Pulse Formation
The target range can be measured accurately only when the display of
the echo signals remains stationary on the sweeps of the range indicators
or when the movement of the target signal on the indicator screens is
caused only by the displacement of the target in space. Therefore,
the moment the transmitter fires the pulse should always coincide with the
moment the electron beam passes the definite point on the sweep which will
correspond to the range scale zero.
The moment the electron beam passes the mentioned point is determined
by the phase of voltages creating the sweep. This phase always corresponds
to the definite phase of the crystal Oscillator voltage. This is obtained
by the use of the trigger oscillator pulses of 74.955 Kc/s for formation
.../of trigger
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011.,unik.
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?
of trigger pulses. The trigger pulses (of a frequency of 1.875 Kc/sec)
make the station transmitter operative.
The trigger pulses of the required frequency are formed in the selector
to which the trigger oscillator pulses of 75 Kc/s and strobe pulses are
furnished. The strobe pulses are formed by the circuit composed of
multivibrator 1.875 Kc/s, a limiter, a gating delay and trigger pulse
electron relay, a strobe pulse width electron relay and a cathode follower.
The multivibrator 1.875 Kc/s synchronized by the voltage from the
multivibrator 3.75 Kc/s, produces an A.G. voltage of approximately square-
wave form whose frequency is 40 times as low as the crystal oscillator
frequency. This voltage is used for triggering the gating delay and
trigger pulse electron relay in which the pulse of regulated duration is
formed.
The trailing edge of the pulse of regulated duration triggers the strobe
pulse width relay which produces strobe square-wave pulses of 9 microsec.
duration. These pulses are applied through the cathode follower to the
trigger selector which passes only those pulses of the trigger oscillator
that are timed with the strobe pulses.
By changing the value of the strobe pulse delay within the range of
0 to 80 microsec. the strobe pulse may be timed with any of the five trigger
pulses coming in succession with 13.3 microsec. pulse interval. In this
case the trigger pulse is formed at the trigger selector output, corresponding
to the range zero and used to trigger the transmitter and the plan-position
indicator unit.
Formation of Gating Pulses for the Brightening of the Sweep
of Coarse Range Indicator
Between two trigger pulses adjacent in time the electron beam of the
coarse range indicator makes two complete revolutions. As a result an error
in target range may arise. For instance, if the distance between the
.../station and
SECRET
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-119-
station and two targets is 10 and 50 km. respectively, the target echo
signals on the screen of the coarse range indicator will be observed at the
same point on the sweep corresponding to 10 km.
To avoid errors when determining the range the sweep of the coarse
range indicator is brightened only for the period of the first revolution
of the electron beam after every trigger pulse. For the remainder of the
time in which the electron beam performs a second revolution, the tube is
not brightened and targets at a distance of 40 km. or more are invisible on
the screen.
The brightening voltage gating pulses furnished to the control
electrode of the coarse range indicator are formed with the help of the
gate width electron relay, generating positive square-wave pulses of
regulated duration (from 0 to 270 microsec.).,
The gate width electron relay is triggered by the gating delay and
trigger pulse electronrelay, and therefore, the beginning of the coarse
range indicator gating coincides with that of the strobe pulse and leads the
beginning of trigger pulses by approximately half of the strobe pulse
duration (600 m, on the scale). Thus the radiated pulse can always be seen
on the screen of the coarse range indicator.
Strobe Pulse Formation
To determine the range more accurately the range measuring system is
provided with a fine range indicator whose screen displays any two-kilometre
section of the coarse range indicator sweep on a larger scale.
For a period between two successive pulses fired by the transmitter
the electron beam of the fine range indicator should make 40 revolutions.
Therefore, the displays of the target echoes obtained on various revolutions
of the sweep are superimposed, thereby making it impossible for the operator
to det,ermine on which revolution of the sweep after the transmitter pulse
one or another echo is displayed.
SECRET
.../To avoid
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- 120 -
?
?
?
To avoid this it is necessary that only that section of the sweep be
brightened on the fine range indicator which corresponds to the sweep
section selected on the coarse range indicator.
The selected sweep section of the fine range indicator is brightened
by the strobe pulse applied to the control electrode of the fine range
indicator. In addition, the strobe pulse is used as an electronic marker
on the coarse range indicator.
By matching the electronic marker (strobe pulse) of the coarse range
indicator with the echo signal it is possible to determine the target range,
i.e. to measure the time between the moment the transmitter pulse is fired
and the moment the signal reflected front the target arrives. The time
delay of the strobe pulse relative to the trigger pulse corresponds to the
slant range of the matched target. This range is read on the scale of the
range mechanism.
The strobe pulse forming circuit utilizes four valves of the strobe
pulse delay circuit, a strobe width electron relay and a cathode follower.
The strobe pulse is set on the sweep by means of the range handwheel
which is mechanically coupled to the shaft of the strobe pulse delay
potentiometer. Taken from the potentiometer slider is a D.C. voltage
which changes linearly when rotating the handwheel and is applied to the
strobe pulse delay circuit.
The strobe pulse delay circuit is composed of a control valve, a trigger
valve, a limiter and a quenching valve. The trigger pulses are applied
to the delay circuit from multivibrator 1.875 Kc/s. The saw-tooth
oscillator (phantastron) provided in the circuit produces linearly decreasing
saw-tooth voltage of 1.875 Kc/s. At the moment the amplitude of the saw-
tooth voltage equas the value of voltage fed from the slider of the strobe
delay potentiometer, the strobe delay circuit triggers the strobe width
electron relay. The saw-tooth pulse duration ensures the strobe delay
from 0 to 40 km.
circqprr
.../The strobe
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The strobe width electron relay squares positive and negative strobe
pulses of regulated duration. Positive strobe pulses are applied through
the cathode follower to the selector of the very narrow gate circuits to
the control grid of the fine range tube for gating the sweep and thence to
the plan-position indicator tubs for gating the corresponding range section.
The strobe pulses of negative polarity are applied to the cathode of the
coarse range tube to produce an electronic marker in the form of a bright
spet on the sweep trace.
Formation of Very Narrow Gate and
Electronic Marker of Fine Ranc,e Indicator
Very narrow gate pulses of 0.3 microsec. duration serve to make the
receiver automatic tracking channel conducting when the signal reflected
from the selected target arrives to trigger the strobe forming circuit in
the automatic range finder unit and to trigger the electronic marker forming
circuit. When the very narrow gate has the above durations the range
resolution is practically about 125 m.s i.e. the antenna positioning system
will ensure accurate tracklng of either of the two targets which differ in
range by not greater than 125 m. (at manual range tracking).
Used as a reference voltage to obtain the very narrow gate is the
sine-wave voltage of the crystal oscillator.
The voltage of 75 Ko/s is applied to the input amplifier in the range
mechanism unit and then to the cathode follower and the phase shifter.
The phase shifter produces a voltage whose phase changes linearly with
rotation of the phase shifter rotor. The latter is mechanically coupled
to the range handwheel. The voltage shifted in phase is amplified and is
applied to the clipper-amplifier in the range indicator unit.
? The voltage at the clipper-amplifier output, has an. approximately
square-wave form. The clipper-amplifier vcltage is used for shocking the
oscillatory circuit in the selector grid circuit into excitation. The
control grid of the selector produces positive and negative pulses of
MUT .../75 Kc/s. Simultaneously
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75 Ko/s. Simultaneously the selector suppressor grid isfed with positive
strobe pulses, When the strobe pulse is timed with one of positive pulses
of 75 Eb/s the selector produces the pulse triggering the very narrow gate
blocking oscillator.
The very narrow gate blocking oscillator generates narrow back-to-back
saw,-tooth pulses of positive and negative polarity* The positive pulse
is furnished to the receiver and the automatic range finder, the negative
one - to the electronic marker forming circuit which includes two blocking
oscillators and a delay line or 0,4 microsec.
Connected into the first cathode circuit of the blocking oscillator
is the delay line for 0.4 micro sec. opened at the end. The very narrow
gate pulse triggers the first blocking oscillator and a positive pulse is
developed across the cathode resistor, which is reflected from the end of
the open line and in 0*8 microsec. appears on the cathode resistor. From
the cathode load two pulses shifted in time by 0.8 microsec. are applied to
the second blocking oscillator of the electronic marker. In the cathode
circuit of the second blocking oscillator two back-to-back saw-tooth pulses
are produced Which are supplied in succession to the cathode of the fine
range indicator foxming two gaps on the sweep trace, i.e. the electronic
marker.
The range is determined accurately by setting the electronic marker
of the fine range indicator symmetrically relative to the echo signal so
that the end of the first and the beginning of the second mark of the
electronic marker are equally spaced from the sweep line, the target range
may be read on the scales of the range mechanism unit.
-Principle of Automatic RaII.92.T.Eackirja
A simplified functional diagram of the automatic range tracking
follow-up system is shown in Fig. 91.
The automatic range trackilg circuit ensures continuous automatic
tracking of a target at the distance of 0.5 to 35 km. from the station,
SECRET
.../The automatic
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77 auumol
- 123 -
?'t
The automatic range finder allows the tracking of targets moving at a speed
----------'?i
0:fIo-250-m/seci '- -
Provision is made in the mechanism for manual target tracking in range
with the help of the manual tracking handwheel. The target is tracked
manually when automatic target tracking is impossible.
To track the target automatically in angular coordinates the receiver
automatic tracking channel should be made conducting at the instant the
signal returned from the moving target arrives. The moment the very
4111 narrow gate appears is determined by the position obtained by the shaft of
the phase shifter and the shaft of the strobe potentiometer, i.e. by the
position of the range mechanism. Thus, the follow-up system must
automatically rotate the range mechanism at the speed the target slant
range changes.
The very narrow gate pulse triggers the split gate forming circuit
through a delay line of 0.17 microsec.
Two square-wave pulses equal in amplitude and duration are obtained at
the output of the gate forming stages, the end of the first pulse being
matched with the beginning of the second. Thus two pulses are accurately
aligned with the very narrow gate pulse. Pulses of 0.6 microsec. duration
ensure the range resolution of 200 m.
The delay value (0.17 microsec.) is selected so that at the instant the
pulses on the discriminator symmetrically divide the video signal, the very
narrow gate passes the signals from the target being tracked through the
receiver automatic tracking channel. In this case the electronic marker
on the fine range indicator is set symmetrically relative to the target echo.
The video, signals from the receiver range channel are amplified by the
video amplifier in the automatic range finder and are furnished to the error
signal time discriminator. The discriminator separates the target echo
from other signals and halves it.
.../The separated
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The separated pulses are converted in the error signal discriminator
in D.C. voltages and the difference of "areas" of the separated pulses
determines the value of the error signal. Both separating signals are
produced during transmission of every pulse.
The error signal is amplified by the D.C. amplifier and from the
cathode follower is applied to the converter. Taken from the converter
transformer secondary winding is an A.C. voltage of 50 c.p.s. modulated by
the error voltage.
? The error voltage of 50 c.p.s, is amplified by the resonance amplifier
?
whose amplification factor is automatically regulated by changing the bias
on the control grid. The bias voltage is developed by detecting (in the
AGO detector stage) the video signal applied from the automatic tracking'
unit.
The amplitude of the video signals depends upon the change on the
target range. A decrease in the video signal amplitude (at the same error
value between the split gate and the signal) causes a decrease of the
error signal, as the difference of the separated pulse "areas" decreases.
The AGC in the D.C. amplifier ensures constancy of the common
amplification factor of the automatic range finder tracking system over the
entire band of target tracking in range.
The error voltage of 50 c.p.s is applied to the control winding of
the automatic tracking motor in the range mechanism unit. Depending on
the value and phase of the voltage the motor drives the range mechanism,
following up the error signal and ensuring continuous symmetrical alignment
of the electronic marker with the target echo signal on the fine range tube.
3. RANGE UNIT
A key diagram of the range unit is presented in Fig.92 (See Album).
The front panel and the unit top view are shown in Figs 93 and 94.
.../The voltage
1ECRET
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The voltage wave forms in separate stages of the range unit and their
time relations are shown in Fig.95.
?
?
Crystal Oscillator
The crystal oscillator is designed to obtain a sine-wave voltage of
75 Ke/s (74.955 Kc/s more precisely) having high stability in frequency.
The application of the crystal makes it possible to ensure constancy
of the frequency of the voltage produced by the oscillator within - 4 c.p.s.
at temperature variations .:!rom -40 to +60?C. In this case the range
measuring errors caused by the oscillator frequency drift do not exceed
1.2 m. (at a distance of up to 40 km.).
The crystal oscillator is based on an electron-coupled circuit
employing valve V8-1 (61(3) which functions as a self-excited oscillator and a
sine-wave voltage amplifier. In the oscillator circuit the valve screen
grid functions as the plate. Used as negative feedback voltage is a
voltage developed across choke L8-1 located in the cathode circuit. The
plate circuit of the valve is used to amplify the voltage of 75 Kc/s.
The range unit is provided with two crystals 1(8-1 and 1(8-2. One of
them is an operating crystal, the other is a spare one. The crystals are
switched over by setting the spars crystal in place of the operating one.
When sustained oscillations of 75 kc/s are established in the circuits
of the control and screen grids of valve V8-1 the plate current of the
valve will contain the D.C. component of the same frequency. Connected
into the plate circuit of the valve is the primary circuit of phase shifting
transformer Tr8-1. The circuit of the transformer contains two resonant
circuits and two coupling coils.
The phase shifting transformer produces two sine-wave voltages, shifted
in phase by 90? with respect to each other, which are taken from the coupling
coils.
These two voltages are fed outto the range and very narrow gate
indicator, thence they are applied through resonant step-down transformers
RFPFITT
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esn. 6,157V!
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? 126 ?
?
?
to two pairs of deflecting plates of the fine range indicator to form the
circular sweep.
The primary and secondary circuits of transformer Tr8-1 are tuned to
the frequency of 75 Kc/s and have weak coupling between each other. The
weak coupling is selected to diminish the influence of one circuit on the
resonance curve of the other circuit.
The primary circuit coil is tightly coupled with its coupling coil.
These two coils have a common alsifer core with a shaft brought out on top
of the transformer housing. The secondary circuit coil is also tightly
coupled with its coupling coil and the shaft of their common alsifer core
is brought out through the base of the transformer housing.
The A.C. component of current1 flowing through coil L8-2 of the
primary circuit creates a variable magnetic field due to which alternating
E.M.F.E29 lagging in phase by 90o from current1, is induced in coil
410 L8-3 of the secondary circuit (Fig.96).
?
Electromotive force E2 produces current 12 in the secondary circuit
which in case of resonance tuning of the secondary circuit is in phase with
electromotive force E2. Thus with the tuned secondary circuit the currents
of the primary and secondary circuits prove to be shifted in phase by 90?
with respect to each other. These currents induce electromotive forces
E3 and E4 in the coupling coils, which lag the currents by the same angle
of 900. Therefore, the electromotive forces in the coupling coils prove to
be shifted in phase by 900 as well.
Provision is made in the crystal oscillator circuit for the following
four regulations which ensure the correct form and diameter of the sweep
on the fine range tube:
1. Resonance tuning of the primary circuit of the phase shifting
transformer to the oscillator frequency. The tuning is carried out by the
alsifer core with a shaft brought out to the top of the transformer housing
and by variable capacitor C8-54 whose movable plate shaft is brought out
WES .../to the
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-127-
to the front panel of the unit and is marked GENERATOR. With resonance
411 tuning of the phase shifting transformer primary circuit maximum voltages
are developed across the coupling coils and, consequently, the maxim=
diameter of the circular sweep on the fine range indicator is obtained.
2. Regulation of the diameter of the fine range indicator sweep which
is done by changing the voltage on the screen grid of valve V8-1. The
change of this voltage causes the change of the amplitude of the crystal
oscillator A.C. voltage and therefore the amplitude of the voltages taken
from the coupling boils of the phase shifting tranSformer. The screen grid
voltage is regulated by variable resistor R8-16 whose shaft is brought out
to the right-hand part of the unit front panel and is marked DIAMETER.
3. Tuning of the secondary circuit of the phase shifting transformer
to obtain the required phase shift between the sweep voltages. This
tuning is carried out by the alsifer core with a shaft brought out to the
bottom of the transformer housing and by variable capacitor 08-58 whose
movable plate shaft is brought out to the right-hand part of the unit front
panel and marked PHASE. At accurate tuning of the transformer secondary
circuit to the crystal oscillator frequency the phase shift between the two
sweep voltages becomes equal to 900. If in this case the amplitudes of
both voltages are the same the sweep assumes the shape of correct
circumference. When the secondary circuit is detuned the phase shift
between the two sweep voltages differs from 900 and the sweep assumes the
shape of an ellipse whose axes occupy inclined position relative to the
planes of the tube deflecting plates.
4. Balancing the amplitudes of the two sweep voltages, which is
effected by variable resistor R8-38. Its shaft is brought out to the
411 right-hand part of the unit front panel and is marked BALANCE.
Tuning with the aid 3f the alsifer cores is usually done in the
manufacturing plant; it should not be carried out when the set is in use,
.../unless it
?
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?
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unless it is impossible to arrive at correct tuning by using controls
brought out to the front panel of the unit (for instance due to considerable
change in the climatic conditions).
If the phase shift between the two sweep voltages is 90? though the
amplitudes are not equal, the sweep trace assumes the shape of an ellipse
whose axes are parallel to the planes of the tube deflecting plates.
Variable resistor R8-38 makes it possible to change the quality factor
of the tuned secondary circuit and thereby change the amplitude of the
voltage taken from the appropriate coupling coil.
It should be borne in mind that the regulation of the phase shift
between the two sweep voltages slightly changes the relationship of these
voltages, while the regulation of the amplitude of the voltage taken from
the coupling coil slightly changes the phase shift between the two sweep
voltages Therefore when tuning the unit it is necessary sometimes to
perform alternately both last regulation procedures (by potentiometers
PHASE and BALANCE) until the sweep assumes the shape of correct circumference
on the screen of the tube.
Trigg2I_Illse Oscillator
The trigger pulse oscillator employing the right-hand triode of valve
V8-6 (6N8S) is a buffer stage placed between the crystal oscillator and
succeeding stages which serves at the same time to convert the sine-wave
voltage of 75 '