RD 54 TASK 5 PHASE I PROGRESS REPORT #2 - MODEL C

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03300A001600010025-5
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 8
• Document Creation Date: December 22, 2016
• Document Release Date: December 28, 2011
• Sequence Number: 25
• Publication Date: February 10, 1956
• Content Type: REPORT

Declassified in Part - Sanitized Copy Approved for Release 2011/12/28: CIA-RDP78-0330OA001600010025-5 """
RD 54 CONFIDENTIAL
TASK 5
PHASE I
PROGRESS REPORT #2 - MODEL C
10 FEBRUARY 1956
5 COPIES DISTRIBUTED AS FOLLOWS:
3 copies to:
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1 copy to:
ET
NF
DENTIAL
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RD 54
TASK 5
PHASE I
PROGRESS REPORT #2 - MODEL C
10 FEBRUARY 1956
OBJECTIVE:
To study and evaluate factors and components involved in the design of a
miniature infrared voice communicator. To plan and schedule the con4plete
task 5 for the production of Model C equipment.
DATA:
Scheduling.
Delays in the construction of the breadboard optical unit prevented
holding the study phase conference as originally planned during the week
of 23 January. Instead, it was held on 8 February.
Technical Study.
1. General:
The parts for the breadboard optical unit were completed and
assembled. In operation tests in the laboratory dark tunnel the
unit has performed very satisfactorily when used with a Model B
equipment. The push-to-talk switch for controlling the transmitter
lamp was found to be convenient and of definite value in lengthening
battery life.
While the value of simultaneous operation of the receiver and
transmitter during "find" is evident from theory, there may be
some field conditions in whidh the backscatter from the trans-
mitter would interfere with reception. The equipment has not yet
been taken into the field to evaluate these effects.
2. Range Tests:
A series of range tests were made using the laboratory dark
tunnel and the vacuum range optical attenuator. The breadboard
receiver and transmitter optics were 1-1/2" diameter, 1-1/2"
focal length systems similar to those used in the Model D equipment.
However, each was equipped with a 1" square aperture mask to
simulate the optics proposed for this equipment. Both apertures
were fitted with Jena type UG-8 filters of 2 mm thickness.
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A Kodak Ektron lead sulfide cell of 1 mm square size and a
3/4 watt lamp were used.
In tests made with a- Model B equipment a vacuum range of
about three- land-miles *as attained. This would indicate an
average clear weather (ACW) -range of about two miles. Since the
mirror in the repaired Model B prototype used in these tests was
not-up to production standards of quality, further tests will be
made- with -another mirror. It is expected that even better results
will then be obtained.
Tests of the Model C breadboard transmitter operating to the
Model C breadboard receiver indicated a vacuum range of about
1-1/4 miles which would give an ACW range of about one mile.
3. Optical System:
a. Lenses.
The results of the breadboard range tests confirm our
original predictions that 1" square apertures would be more
than adequate to achieve the specified minimum ranges. The
use of a square aperture was planned because of the greater
modulation linearity as compared with a round aperture. How,
ever, since under normal modulation the signal applied to the
galvanometer undergoes considerable clipping to increase the
average modulation percentage and to protect the galvanometer,
the question of minor additional -distortion introduced by the
modulation system may not be important. The effect of
harmonic distortion in the transmitted signal is minimized by
the limited high frequency response of the galvanometer itself
as well as the characteristic of the lead sulfide receiving cell.
To determine the effect of a square transmitter aperture
on overall system voice quality several listening tests were
performed in which both round and square apertures were used.
Preliminary tests indicate a relatively slight difference in
quality but further listening tests as well as quantitative
distortion measurements will be made.
If no significant improvement is obtainable with the square
aperture, round lenses will be used and the mechanical
fabrication problem will be greatly simplified. Otherwise
square lenses and mounts would be required or round lenses and
mounts with a square mask and its attendant loss in aperture
area.
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The final choice of lens diameter will be made after the
lens shape has been decided. As large an aperture as possible,
within the basic size limitations, will be chosen. If a slight
increase in case thickness above the basic 1-1/2" dimension
is required for the lenses, the case can be flared out slightly
at that point.
b. Galvanometer and magnet.
Midwestern Instruments said they believe their Model 102
galvanometer can be modified to meet our requirements. Their
estimates predict a sensitivity of 12 ma. /inch at a 12" optical
arm. The coil resistance is estimated at 30 ohms. The
maximum safe continuous current would be 100 ma. while a
current of 170 ma. would be safe for a few seconds or less.
With an fl-1/8 system a peak angular deflection of about
12 degrees is required; this corresponds to a 5. 3 inch
deflection at a 12" optical arm. Thus, for the predicted
sensitivity a peak current of 64 ma. (5. 3 in. x 12 ma. /in.)
would be required. With a 30 ohm coil this corresponds to
about 62 mw average power requirement for 100 per cent
modulation. A power of greater than 300 mw would be re-
quired to exceed the maximum safe current of the galvanometer.
A modulator designed to produce 75 mw of power and capable
of at the most perhaps 125 mw would require no fuse in the
output circuit for galvanometer protection.
Some details as to the exact mechanical configuration of
the galvanometer must be settled and then a definite order can
be placed. Midwestern Instruments' quotation specifies a
fixed $300 charge for design modifications and a unit price of
$120.
Preliminary work has been done on the magnet and pole
piece design and sample quantities of magnets have been
ordered for testing.
c. Modulation indicator.
A neon bulb type modulation indicator, operated from the
modulation amplifi4r output, is impractical as: (1) the avail-
able audio voltage is not sufficient to strike a glow, and (2) the
neon bulb would waste too much power even if sufficient voltage
were available. Instead, a system will be used in which a small
portion of the visible modulated light from the galvanometer is
displayed at a small indicator window to provide an indication
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of modulation depth. A simple mechanical shutter will provide
for dimming and complete shut-off of the visible light.
A modulation indicator of this type has the additional
advantage of showing actual modulation of the light and there-
fore serves to check the galvanometer operation. It would
indicate the condition of the lamp and, indirectly, the batteries
by judging the brightness of the light.
d. Lamp.
Sample lamps of about 1/2 watt and 3/4 watt sizes have
been obtained and tested. As mentioned in section 2, the
reported ranges were obtained with the 3/4 watt lamp. Tests
were made with a 1/2 watt lamp show a signal reduction of
about 3 db as compared to the 3/4 watt. The lower power lamp
has essentially the same filament size and therefore operates
at a lower brightness. At this time the 3/4 watt lamp appears
to be a good choice in view of range and battery life requirements.
e. Cell.
The range tests discussed in section 2 were made using a
Kodak Ektron 1 x 1 mm lead sulfide cell. This is the sate as
those used in the Model B equipments. It appears to bt
entirely satisfactory and no change is contemplated.
f. Sights.
Open sights are recommended because of their simplicity
and small size. At night they would be superior to a small
telescopic sight of necessarily limited light gathering ability.
A dot of luminous material can be provided on the front sight
for night use.
4. Amplifiers:
a. Receiver.
A three stage transformer coupled amplifier has been
built in breadboard form. A 2N133 low noise type transistor
in the first stage has enabled the noise referred to the input to
be reduced to about 3 microvolts. The overall amplifier
voltage gain is in the order of 80 db. Temperature stabilization
is being investigated and at present the change in gain over the
temperature range of 0?C to 50?C appears to be satisfactorily
small. Power requirements for the amplifier are 4. 5 to 5. 5
volts at about 3 ma.
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b. Modulator.
There has been no further development of the modulator
amplifier during this period but additional components for test
have been ordered and received.
5. Batteries:
Two general types of batteries are required. One 15 volt
battery is needed for cell bias supply and four 1.2 to 1. 5 volt cells
are required for the amplifiers and lamp. For the cell bias, a
battery such as the Burgess Y10 or the Eveready 404E will be used.
This battery size is about 5/8" x 5/8" x 1-3/8" and weighs 1/2
ounce. At the normal cell current drain of 20 microamperes the
battery life at 70OF would exceed 3000 hours.
For the low voltage cells several types have been, considered
and tested. A 3/4 watt lamp was used as a load across two series
connected cells under test. A very low frequency transistor multi-
vibrator was built to form a test circuit for turning the load "on" and
"off" in about 45 second intervals. All tests were made at room
temperature.;
Mallory RM12R mercury cells gave two hour discharge periods
(to 1.9 V endpoint) for two successive days and a one hour period
the third day.
Samples of Gould Multi-Lite nickel cadmium storage cells of
AA size were purchased. Two of these were tested with the same
test setup as above. They gave two hours operation the first day
and about 15 minutes the second, before recharging was required.
Normally a 10 to 12 hour charge period at an 80 ma. rate is
required. When charged at this rate the cell can be overcharged
indefinitely. without harm, thus allowing the use of a very simple
charger. Although the manufacturer has not obtained enough data
at this time to state the ultimate life of the AA size cells they state
that the D size cell is good for approximately 250 charge-discharge
cycles. The cells are hermetically sealed, thus preventing
electrolyte leakage problems.
Eveready size AA dry cells were tested under similar load
conditions and 30 minutes of operation were obtained the first day,
20 minutes the second, and 10 minutes the third. Thus, although
giving very limited service life, they might be useful if other types
were not available.
Since all three of these battery types are in the same general
size range, it is thought advisable to arrange the mounting and
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contact clips in the equipment to accommodate all types so that
any available type may be used. The low voltage power require-
ments of the equipment will be met with four cells connected in
series. The series will be tapped at two cells to provide power to
the lamp at 300 to 350 ma while the amplifier will be connected
across the entire series and only require about 15 ma. Thus, when
the two cells powering the lamp are down they may be interchanged
with the other two which would still be near full capacity. A useful
increase in battery service can be obtained in this way.
6. Mechanical Considerations:
It appears at this time that the basic case dimensions of
6" x 4-1/2" x 1-1/2" can be maintained. However, at certain
points these dimensions will be exceeded by various projecting parts.
Thus the open sights will increase the 4-1/2" dimension slightly
at two points. Probably the lenses will increase the 1-1/2"
dimension slightly where the case may be flared out. The lenses at
the front or the control knobs at the back may increase the 6"
dimension somewhat. Efforts will be made to hold such increases
to a minimum however.
Estimates of the equipment weight indicate that it will be in the
neighborhood of 2-1/4 lb. Of this amount, about .7 lb. is allowed
for the case, chassis, etc.; .4 lb. for the batteries; and 1.1 lb. for
optical system and electronics.
A Rowi (Germany) no. 76 camera clamp has been obtained for
study. Its general features make it fairly good as an accessory clamp
for mounting the equipment. However, the clamp jaw opening of
1-1/8" is too small for many applications. An opening of 1-1/2"
would be more useful. Other clamps will be studied to determine if
a somewhat more versatile clamp is available.
PROGRAM FOR NEXT INTERVAL:
Additional vacuum range tests will be made with the breadboard Model C
and the Model B equipped with a different. mirror. If possible, some field
tests will be conducted as well. Further tests will be performed to
determine the effects of aperture shape on overall system distortion and on
the basis of these tests a decision will be made regarding lens shape. It
will then be possible to determine definite lens specifications and place an
order for their design and fabrication.
The order for the galvanometer modulators will be placed as soon as the
final details of mechanical design are settled. Further work on the magnet and
pole piece assembly design will be done.
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It is expected that the receiver amplifier circuit development will be
completed and work will start on the modulator circuit development.
Preliminary mechanical design can proceed as the questions regarding
lens size and shape and magnet design are resolved.
Report prepared by:
Report approved by:
CONITM.E TIAL
BECYZL~Y"~ 7
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