OPERATING AND MAINTENANCE MANUAL FOR TRANSMITTER RT-3R AND POWER SUPPLY RT-3PS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03642A000300010001-6
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 33
• Document Creation Date: December 22, 2016
• Document Release Date: May 29, 2012
• Sequence Number: 1
• Content Type: MISC

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CONFIDENTIAL
COPY_OF 305
L148
OPERATING AND MAINTENANCE MANUAL
for
TRANSMITTER RT-3R
and
POWER SUPPLY RT-3PS
COPY,/_OF 305
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CONFIDENTIAL
Section
1.1 Scope
1.2 General Description
1.3 General Specifications
1.4 Equipment List
TABLE OF CONTENTS
PART I
TRANSMITTER TR-3R
1. INTRODUCTION
RT-3R
Page
1-2
1-2
2.1 General
2.1 Detailed Description
a. R. F. Section
b. Audio Section
c. Battery Supply
2. CIRCUIT DESCRIPTION
3. Operation
3.1 General
3.2 Test Equipment
a. Required
b. Optional
3.3 Operating Procedure
a. Identification of Frequency Range
b. Operation
c. Identification of Adjustments
3.4 Setting Deviation Sensitivity
a. Setting Deviation With Laboratory Equipment
b. Setting Deviation Without Laboratory Equipment
L148
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1-8
i-8
1-8
i-8
1-8
1-8
1-8
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CONFIDENTIAL
Section
RT-3R
Page
3.5
Frequency Check
1-12
3.6
Frequency Adjust
1-12
a. Oscillator Tuning
1-12
b. Peaking The Output
1-12
4. MAINTENANCE
4.1
General
4.2
Accessibility
4.3
Battery Replacement
I-14
4.4
Test Equipment
I-14
a. Required
I-14
b. Optional
I-14
4.5
General Precautions
I-14
4.6
Sectionalizing And Localizing A Fault
1-15
a. Visual Inspection
1-15
b. Operating and Alignment Test
1-15
c. Intermittents
1-15
4.7
Troubleshooting Chart
1-15
4.8
Voltage-Resistance Chart
1-17
5. PARTS LIST
LIST OF ILLUSTRATIONS
Figure No.
Page
I-1
Photograph-Transmitter RT-3R
I-1
Schematic Diagram-Transmitter Circuit
1-6
1-3
Photograph-Component Layout and Test Points
1-7
I-4
Illustration-Battery Packs in Parallel
1-9
1-5
Illustration-Test Setup for Deviation Measurements
1-9
L148
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CONFIDENTIAL
Parallel Connector
Figure I-1 TRANSMITTER RT-3R
L14+8
CNN I DEN I A L
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RT- 3R
1. INTRODUCTION
1.1 SCOPE
Part I of this instruction manual contains information for the operation
and maintenance of the transmitter, Model RT-3R. The equipment is shown in
Figure I-1.
1.2 GENERAL DESCRIPTION
It is an improved version of the RT-3. Transistors and
subminiature components have been used to minimize size'and reduce power con-
sumption. The unit may be battery-operated, or may operate on either 110 vac
or 220 vac when used with a power supply, as outlined in Part II of this manual.
1.3 GENERAL SPECIFICATIONS
Operating Frequencies - 55 me to 63 me
61+ me to 72 me
73 me to 81 me
Type Modulation
- Frequency Modulation
Deviation Sensitivity - Adjustable (minimum setting of control
produces between 1 kc/100 gv to 3 kc/
100 ?v. Maximum setting of control
produces 15 kc/100 gv to 20 kc/100 ?v.
(5 kc/100 ?v and 10 kc/100 gv points
are clearly indicated by green and red
marks respectively.)
Audio Frequency
Hum and Noise
Microphone
R. F. Power Output
D C Power Input
Voltage
Current
Output Impedance
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- +1 db between 500 cps and 5 kc, not
more than 3 db down from 1 kc at 200
cps and 10 kc.
25X1
25X1
25X1
- .5 kc maximum
MC-30 microphone supplied 25X1
- 7 mw or greater
- Approximately 65 mw maximum
- 6.5 +.5
- 10 ma or less
- Approximately 50 ohms
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RT-3R
Antenna - Quarter wave whip antenna supplied
Dimensions - Approximately 3 13/16" x 1 3/4" x 3/4"
Weight - Approximately 6 oz.
Finish - Black wrinkle
1.4 EQUIPMENT LIST
a. Transmitter
1.) Microphone
2.) Antenna
3.) Tuning Tool
4.) Power Cord Extension
5.) Three (3) Antenna Connectors
6.) Three (3) Microphone Connectors
b. AC Power Supply
c. Battery Pack
L14 8 I-3
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RT-3R
2. CIRCUIT DESCRIPTION
2.1 GENERAL
The complete transmitter circuit is shown in Figure 1-2. The circuit consists
of a frequency modulated oscillator, Q3; an r.f. amplifier, Q4; and a two-stage audio
amplifier, Qi and Q2.
Modulation is accomplished by varying the reactance of the diode modulator CR1.
The operating frequency is determined by the Oscillator Tuning Adjustment, incorpo-
rated in Ti. Modulation sensitivity is controlled by the setting of potentiometer,
R5.
2.2 DETAILED DESCRIPTION
a. R.F. Section
Oscillator Circuit
Q3 is the oscillator transistor, connected in the common base con-
figuration. The oscillator output tuned circuit consists essentially of
the primary of T-1 and C13. C14 (a negative temperature coefficient ca-
pacitor) compensates for changes in frequency due to temperature. Modu-
lation is accomplished by the diode CR1 which acts as a variable capacity
with changing bias. C10 is an r.f. voltage dropping capacitor, selected
for proper modulation sensitivity and linearity. R14, R15, and R16 provide
temperature stable operating bias for the oscillator. C9 and C11 are r.f.
bypass capacitors. Feedback, required to maintain oscillation, is provided
by C12. RFC1 is an r.f. choke. R13 is an isolating resistor, used to pre-
vent Q2 from shorting out the r.f. at CR1. R17 and R18 are DC bias resis-
tors for CR1. C16 is an audio coupling capacitor.
R.F. Amplifier Circuit
Q4 is the r.f. amplifier transistor, connected in the common emitter
configuration. The oscillator output is coupled to the r.f. amplifier
input through T1. Tuning is accomplished by adjusting the tuned circuit
of T2. The frequency amplified'is primarily determined by the value of
T2 and the resonating capacitor, C8. C7 is an r.f. bypass capacitor.
R12 is a current limiting resistor for the r.f. amplifier stage. J2
is the antenna connector.
b. Audio Section
Audio Amplifier Circuit
Q1 is the first audio amplifier transistor, connected in the common
emitter configuration. J1 is the microphone input jack. The microphone
output is coupled to the base of Ql by Cl. C2 performs two functions:
(1) decoupling capacitor, (2) ripple filter. Rl and R2 form a voltage
divider to provide base bias for Ql. The combination of Ri, R2, and R4
provides temperature stable dc bias for Qi. R3 is. the collector load
L148 I-4
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RT-3R
resistor. C15 is an r.f. bypass capacitor. C1+ is an audio bypass
capacitor. R8 is a decoupling resistor. C3 is a coupling capacitor
between Q1 and Q2.
Q2 is the second audio amplifier transistor, connected in the
common emitter configuration. The combination of R5, R6, R7, and
R10 provides temperature stable do bias for Q2. Modulation sensi-
tivity is adjusted by means of potentiometer R5. C5 is an audio
bypass capacitor. R9 is the collector load resistor. C6 performs
two functions, (1) decoupling capacitor, and (2) ripple filter. R1l
is a decoupling resistor. P3 is the power input Jack.
c. Battery Supply
The battery supply consists of five (5) "Mallory" RM-12R cells
connected in series and assembled in a cardboard case.
L1148
I-5
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Figure 1-3 COMPONENTS LAYOUT AND TEST POINTS
I-7
RT-3R
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3.1 GENERAL
RT-3R
The transmitter RT-3R is designed to operate continuously and without
attention. Therefore, this section will be concerned mainly with preparing
the unit for use. This may best be accomplished in a laboratory, prior to
final installation.
3.2 TEST EQUIPMENT
a. Required
FM Signal Generator - Boonton Radio Corp., Type 202E, or equivalent
Audio Oscillator - Hewlett Packard, Model 200AB, or equivalent
Microvolter - General Radio, Type No. 51+6-C, or equivalent
Oscilloscope - Dumont, Type 304-A, or equivalent
Receiver - ASR-l, or equivalent (See Section 3-4)
b. Optional
Vacuum Tube Voltmeter - Ballantine, Model 314, or equivalent.
R.F. Indicator - Special
3.3 OPERATING PROCEDURE
a. Identification of Frequency Range
Each unit is set on one of three frequency ranges. A dot of paint is
placed on one end of the transmitter case in order to identify its frequency range,
as follows:
Color Frequency Range
Green 55 me to 63 me
Blue 64 me to 72 me
White 73 me to 81 me
b. Operation
1. Determine whether the transmitter will be battery-operated or
operated from a line voltage of 110 vac or 220 vac. If the
unit is to be operated from line voltage, refer to Part II of
this. manual, Power Supply Operation. If the unit is to be
battery-operated, continue with the next step.
L148
1-8
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2.. Connect the battery-pack supplied, to the transmitter, as
shown in Figure I-l. If it is desired to operate the trans-
mitter longer than the expected life of the battery pack
(360 hours) without changing batteries, two or more packs
may be connected in parallel, as shown below.
Battery Packs
Figure I-4 Battery Packs Connected in Parallel
3. Attach the antenna and the microphone to the transmitter.
4. The unit should now be operating, providing the adjustments
have not been changed since delivery.
c. Identification of Ad ustments (Figure 1-3)
Name Function Ref. Symbol
Deviation Sensitivity Adj. Adjusts the deviation R5
Oscillator Tuning Adj. Sets the operating frequency Ti
Amplifier Tuning Adj. Peaks the Output T2
000
(a (01
FM Sig. Gen.
A:: VTVM
0
FM REC
RT-3R
DUMMY LOAD
or WHIP ANT,
Figure 1-5 Test Setup for Deviation Measurements
RT-3R
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3.1+ SETTING DEVIATION SENSITIVITY
Deviation Sensitivity can be set to any value from 2 kc/100 microvolts to
15kc/lOO microvolts. The 5kc and lOkc points on the Deviation Sensitivity Ad-
justment are identified by a paint mark (5 kc - green, 10 kc - red).
For optimum performance, transmitter deviation should be matched with
receiver bandwidth, e.g., if the PFR-5 receiver is used, transmitter deviation
should be set at minimum; if the ASR-1 receiver is used, deviation should
be set at 5 kc, (green mark). If a receiver is used whose deviation capabilities
are unknown, the following procedure is recommended: (use the test setup shown
in Figure I-5).
1. Connect an *oscilloscope directly to the output of the receiver
(directly to the detector output, where possible).
2. Increase the signal generator output to maximum, set the signal
generator modulating frequency to 1 kc, and adjust the deviation
to 10 kc.
3. Tune the receiver to a clear-channel frequency in the vicinity of
the desired operating frequency.
1+. Adjust the signal generator so that it is properly tuned-in to
the receiver. (This is evident by maximum limiter current and/or
zero reading on the receiver discriminator meter.)
5. Set the oscilloscope for some convenient number of divisions.
6. Reduce the signal level of the signal generator until the receiver
output begins to fall.
Retune the receiver or signal generator as described in Step 1+
above, if necessary.
8. Increase the signal generator output 20 db.
9. Increase the deviation until noticeable distortion appears in the
form of peak clipping. (If the receiver is properly aligned and
tuned-in, both peaks will clip simultaneously; if not, clipping
will occur only on one peak. Slight retuning of the receiver or
signal generator will correct for misalignment.) Retune the re-
ceiver to reduce clipping and increase deviation until. clipping
occurs again.
THE POINT AT WHICH SYMMETRICAL CLIPPING STARTS IS THE MAXIMUM DEVIATION THE
RECEIVER WILL ACCOMMODATE UNDER NORMAL OPERATING CONDITIOP'S. (The band width of the
receiver is 2 x the maximum deviation.) (If the Boonton 202-E signal generator is
used, deviation can be read directly on the deviation meter.) Set the scope to some
convenient level, e.g., peak-to-peak deflection equals 10 divisions. If nearly
symmetrical clipping still does not occur, the receiver is improperly aligned or in
need of repair.
*A vacuum tube voltmeter may be used in conjunction with the oscilloscope, where
greater accuracy is required.
L148
T-10
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RT-3R
a. Setting Transmitter Deviation With Laboratory Equipment
Using the same test setup as shown in the block diagram in Figure 1-5,
continue below:
1. Reduce the r.f. output of the signal generator to zero.
2. Operate the transmitter without attaching the microphone, and
connect the audio oscillator and the microvolter to the trans-
mitter input.
Set the audio oscillator frequency to 1 kc and the microvolter to
500 microvolts. This value (500 microvolts) will provide adequate
sensitivity without overload for normal room conditions.
4. Tune the receiver carefully to the transmitted signal.
5. Rotate the Deviation Sensitivity Adjustment until the receiver
output is equivalent (on the scope) to that obtained from the
signal generator, as in Step 9 above. (To increase deviation,
rotate Deviation Sensitivity Adjustment clockwise. To decrease
deviation, rotate counterclockwise.)
b. Setting Transmitter Deviation Without Laboratory Equipment
There is a red and a green dash painted on the Deviation Sensitivity
Adjustment to indicate the setting, as follows:
For 10 kc/100 p volts deviation, (using a Clarke or Servo receiver) rotate
the adjustment until the red dash is in line, as shown below.
For 5 kc/100 w volts deviation, (using the ASR-1 receiver) rotate the
adjustment until the green dash is in line, as shown below.
For 1-3 kc/100 g volts deviation, (using the PFR-5 receiver) rotate the
adjustment fully counter-clockwise.
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R'P-3R
3.5 FREQUENCY CHECK
The oscillator frequency is the operating frequency. The following two
methods may be used to determine whether the transmitter is operating at the
desired frequency.
Method No. 1
The accuracy of this method depends on the accuracy of the receiver
calibration.
1. Operate the unit in the vicinity of a receiver.
2. Tune the receiver to the transmitter signal. (Proper receiver
tuning is indicated by maximum limiter current and/or zero reading
on the receiver discriminator meter.)
Method No. 2
This method requires that a grid dip meter be used as an absorption
meter. (This method should not be used where accuracy is required.)
1. Operate the transmitter. Then, remove the top cover by removing
the two securing screws.
2. Place the grid dip meter coil parallel to, and as close as
possible, to the oscillator coil.
3. Tune the grid dip meter until a peak is observed. The reading
on the grid dip.meter indicates the operating frequency.
3.6 FREQUENCY ADJUST
a. Oscillator Tuning
If it.is desired to change the frequency of the transmitter, the following
procedure is recommended:
I148
Remove the top cover by removing the two securing screws.
Starting with the Oscillator Tuning Adjustment at its counter-
clockwise extremity (the highest frequency is obtained with
the slug in this position), rotate the slug clockwise until
the desired frequency is obtained.
Peaking the Output
The power amplifier may be tuned,
1. Operate the unit in the vicinity of a receiver, tuned to the
desired frequency.
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RT-3R
2. Remove the top cover by removing the two securing screws.
3. The signal strength~indic'ator on a receiver is very insensitive
to changes in signal level in a high signal strength field.
Therefore, it is recommended that the receiver antenna be one
or two inches in length, so as to prevent saturation of the in-
dicator. Thus, a more sensitive reading of power out may be made.
4. Rotate the Amplifier Tuning Adjustment until a maximum reading
is obtained on the receiver field strength indicator.
5. Where an r. f. indicator or power meter is available, it should
be used to determine the tuning which gives maximum power output.
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4. MAINTENANCE
4.1 GENERAL
RT-3R
The transmitter RT-3R is designed to require minimum maintenance. SLnce
transistors are soldered in place and subminiature techniques are used in the
construction of the unit, little field maintenance is possible. It is recom-
mended that with the exception of minor repairs (broken leads, loose connections,
etc.) and battery replacement, all maintenance and trouble shooting be conducted
in a laboratory.
4.2 ACCESSIBILITY
Both sides of the printed circuit board are easily accessible for servicing
when the transmitter covers are removed. (There are two screws securing each
cover to the case.) The board itself is riveted to the transmitter case for more
rigid construction, and should not have to be removed.
4.3 BATTERY REPLACEMENT
The battery pack should be replaced after approximately 360 hours of
transmitter operation. There is no positive method of determining the condition
of the battery, i.e., to what extent it has been used or its remaining capacity;
therefore, it is recommended that a record of transmitter "on" time be kept. When
there is any question as to the probable condition of the battery, it should be
replaced.
4.4 TEST EQUIPMENT
a. Required
Volt-ohm Meter-Simpson, Model 260, or equivalent.
Vacuum Tube Voltmeter-Ballantine, Model 314, or equivalent.
Receiver-Nems Clarke 1501, or equivalent.
b. Optional
Oscilloscope-Dumont, Type 304-A, or equivalent.
Audio Oscillator-Hewlett Packard, Model 200AB, or equivalent.
Microvolter-General Radio, Type No. 546-C, or equivalent.
Watt Meter-Jones Electronic Corp, Model MM621U, or equivalent.
4.5 GENERAL PRECAUTIONS
Whenever the unit is serviced, carefully observe the precautions listed
below: (careless replacement of parts makes new faults inevitable.)
a. Remove a.c. power before servicing the foil side of the unit.
b. Before a part is unsoldered, notethe position of the leads, and tag
(number) each of the leads.
L148 I-14
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RT-3R
c. Be careful not to damage other connections by pulling or pushing the
leads out of the way.
d. If soldering is performed on the unit, do not allow solder to bridge the
foil at any point, it may cause a short circuit.
e. A carelessly soldered connection may create a new fault. It is important
to use care in soldering; since a poorly soldered joint is one of the
most difficult faults to find.
f. Use appropriate ranges on meters and test sets used for troubleshooting.
g. In replacement of the oscillator transformer, care must be exercised
in the orientation of the windings.
h. In replacing transistors, use a soldering iron with a low power
rating (22 1,2 watts). Excessive heat applied to a transistor lead
may damage the transistor.
4.6 SECTIONALIZING AND LOCALIZING A FAULT
The first step in servicing a defective unit is to sectionalize the fault;
i.e., to trace the fault to the stage or circuit by appropriate voltage and/or
resistance measurements as outlined in Section 4-8, Voltage-Resistance Chart. The
preliminary tests listed below will aid in isolating the source of trouble.
a. Visual Inspection
The purpose of visual inspection is to locate any components which show
evidence of mechanical breakdown. Through this inspection, the repairman may
frequently discover the fault or determine the stage in which the fault exists.
This inspection is valuable in forstalling future failure and in avoiding damage
to the unit which might occur through improper servicing methods.
b. Operating and Alignment Test
It is recommended that the repairman try to operate the equipment, as
directed in Section 3, to determine just what mal-function exists and to check
tuning and alignment.
d. Intermittents
In all these tests, the possibilities of intermittents should not be over-
looked. If present, this trouble may often be made to appear by tapping or jarring
the unit. It is possible that the trouble is not in the transmitter unit itself
but in the auxiliary apparatus, or connections.
11.7 TROUBLESHOOTING CHART
The following chart is supplied as an aid in locating trouble in the unit.
This chart lists the symptoms which the repairman observes, and indicates how to
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RT-3R
localize trouble quickly in the various sections. Normal voltage and resistance
measurements are given in the Voltage-Resistance Chart 4-8, which follows the
Troubleshooting Chart.
SYMPTOM
PROBABLE CAUSE SUGGESTION
No. R. F. Power Output Power supply inoperative Refer to troubleshooting chart
(no or low D C voltage at for power supply RT-3PS in Part
test point 17). II of this manual.
Battery defective or weak Replace battery if voltage is
(no or low D C voltage at less than 6 volts with a 680
test point 17). load.
Defective D C input cable
(no voltage at test point
17).
Defective oscillator
transistor.
If power supply is operating
correctly, check D C input
cable for continuity.
Check D C voltages on the
oscillator. If normal, replace
transistor.
Low R. F. Power Output Low D C input voltage.
Improper tuning.
Measure D C input voltage at
test point 17.
Retune the power amplifier
as outlined in section 3-6b in
Part I of this manual.
Amplifier transistor Check oscillator drive by
defective (low total measuring total current.
current). Normal total current is approx.
9 ma.
Defective audio transistor Check A C and D C voltages
or component. in audio section, and compare
with voltage resistance chart,
Section 4-8.
Distorted and/or Low Improper D C operating Check A C and D C voltages
point resulting from a in audio section, and compare
resistance value change; with voltage resistance chart,
shorted or leaky capacitor; Section 4-8.
or defective transistor.
Distorted and/or Abnormal- Faulty diode CR-1 or Check voltage and resistance
ly High or Low Modulation, improper bias on CR1. on CR-1 at test point 14; compare
but Audio Functioning with voltage resistance chart,
Properly. Section 4-8.
L148 1-16
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RT-3R
High Hum Level Open ground in input cable, Remove input cable.
unshielded input connec- If hum level is reduced,
tion. check for open ground or
unshielded cable.
If power supply is used, Open filter capacitor in
measure A C (ripple) power supply.
voltage,at test points
on power supply.
High Hum Level With
Microphone Connected
Microphone near high Disconnect micros one cable
induction field. and note change in hum level;
re-orientate or relocate
microphone away from hum sources
such as, transformers, fluorescent
lights, appliances, etc.
High Noise Level With Noisy transistor Q1.
Input Circuit Dis- Defective component
connected. Rl, R2, R3, R4, c3, c4.
High Noise Level With Cl defective.
Input Circuit
Closed. (Generator
connected or input shorted)
High Noise, Level inde- Transistor Q2, noisy.
pendent of Deviation Defective component in
Sensitivity Adjustment second audio stage R6,
R9, R10, or C5.
Rotate Deviation Sensitivity
Adjustment fully counter-clockwise
If noise reduces, replace Q1.
If noise level is reduced when
input circuit is opened, replace
Cl.
Measure A C voltage with no
signal output and compare with
voltage resistance chart, Section
4-8.
4.8 VOLTAGE RESISTANCE CHART
D C voltages were measured with a Simpson, Model 260, voltohmeter. Re-
sistances were also measured with a Simpson. A C voltages were measured with a
Ballantine, Model 314, vacuum tube voltmeter.
L148
1-17
Declassified in Part - Sanitized Copy Approved for Release 2012/05/29: CIA-RDP78-03642A000300010001-6
 Declassified in Part - Sanitized Copy Approved for Release 2012/05/29: CIA-RDP78-03642A000300010001-6
Test Points
A. C. Voltage (mv) +10%
(f=1 kc)
D. C. Voltage (volts) +10
%
Resistance (Ohms) +20%
No Signal In
100?v Signal
Pos. Meter
Neg. Meter
In
ad to Gnd
Lead to Gnd.
Ql
2 (c611) to *1(gnd)