PROGRESS LETTER NO. 12 SYSTEM 3 CONTRACT NO. A-101

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81B00878R000300060019-8
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 12
• Document Creation Date: December 12, 2016
• Document Release Date: April 3, 2002
• Sequence Number: 19
• Publication Date: July 4, 1956
• Content Type: REPORT

Approved For Release 20UMCpTDP81 B00878R000300060019-8
Progress Letter No. 12
System 3
Contract No. A-101
4 June 1956 to 4 July 1956
CMCC Document No. 163X5. 7
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(This document contains a total of 14 sheets,
including this title sheet. )
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 Approved FoRelease 206WRETDP81 B008 8000300060019-8
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Paragraph Page
1-0. GENERAL. . . . . . . . . . . . > . . . . . . . . . . , . 1
2-0. SYSTEM DEVELOPMENT. . . . . . ? . . . . ? ? ? ? ? ? 1
3-0. FLIGHT TEST PROGRAM . . . . . . . . . . . . . . . . 2
4-0. TEST SET . . . . . . . . . . . . . . . . . . . . . . . . 6
5-0. PRODUCTION OF SYSTEM 3 . . . . . . . . . . . . . . . 6
7-0. PLANNING . . . . . . . . . . . . . . . . . . . . . . . . 7
(Results of Thermal Tests Appended)
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 Approved For Release 20 CIN-DP81B00878R000300060019-8
1-1. During the present report period construction of the prototype
system was completed and the major effort was expended in
evaluating, refining, and flight-testing the prototype system, and
on expediting the. production of the first systems to be delivered.
2-0. SYSTEM DEVELOPMENT.
2-1. A method of adjusting the lock-on duration has been added to
System 3. The lock-on duration may now be controlled by
inserting a resistor of appropriate value into a clip. By this means,
the lock-on duration can be set to any value between a minimum
of 50 milliseconds and a maximum of two minutes.
2-2. System tests indicated the presence of spurious responses.
These were reduced by adding decoupling filters, by improved
shielding, and by controlling local-oscillator voltages more
carefully. The presence of spurious signals required that the
lock-on sensitivity levels be raised during the test flights
described below. Lock-on was adjusted to function with a minimum
input signal, averaging about ten microvolts. It is expected that
further work will result in an increase of the lock-on sensitivity
toward the design goal of a three-microvolt lock-on level for all
channels.
2-3. Laboratory operating tests of subassemblies were made at
low and high temperatures. At the low end of the temperature
scale, the operation of some transistorized flip-flops became
faulty at component temperatures of -40?C. These reverted to
normal operation when the temperature was subsequently raised.
Since under normal operating conditions sufficient self-heating of
the receiver unit occurs and maintains component temperatures
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 Approved For Release 205ERTDP81 B008 8R000300060019-8
25X1 D
above 0? C, no difficulty is anticipated due to low temperatures. At
the high end of the temperature scale, the transistorized circuits
malfunctioned at component (passive) temperatures of 160?C. Since
system tests indicate maximum temperatures of 107? C, a margin
of safety exists.
2-4. Servicing information is being compiled on the system.
Typical oscilloscope displays have been photographed at a number
of test points on the various assemblies. These will appear in
the System 3 Instruction Guide.
3-0. FLIGHT TEST PROGRAM.
3-1. Three flight tests in the type C-47 aircraft have been
concluded. In the initial flight of this series, emphasis was placed
on temperature measurements and mechanical characteristics.
(See results of thermal tests appended. ) Two additional flights
were made in which a more comprehensive evaluation of both
mechanical and electrical characteristics was made. Although
the lock-on sensitivity of several r-f channels was reduced on the
first two flights because of the presence of some spurious responses,
the results of the flight tests were generally favorable in all other
respects.
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 25X1 D
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4-1. The breadboard model of the test set has been completed,
and the power supply unit has been constructed in finished form.
The layout of the r-f signal generator unit has been completed
and its construction is underway. The counter unit is presently
undergoing mechanical design. The first deliverable test set is
scheduled to be completed on 3 August 1956,
5-0. PRODUCTION OF SYSTEM 3.
5-1. Emphasis is being placed on the rapid completion of the
initial two systems to be used in actual field operations. All
encapsulated components have been assembled. Engineering
drawings have been released for production of the sweep assembly,
and the release of drawings for remaining subassemblies is
imminent, Except for some etched boards, all parts for the
initial two systems have been procured, The initial two systems
are scheduled to be completed on 8 August 1956.
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 Approved For Release 20S TDP81 B00q,78R000300060019-8
6-1. System 3A is the designation given to the modification of
System 3 in which the scan of the system is restricted to any three,
or any six of the 144 spectrum divisions into which the total 50
megacycle frequency range of System 3 is divided. This modifi-
cation is effected, during field use, by the replacement of the
second local-oscillator assemblies by substitute plug-in
assemblies. The basic design of this new assembly has been
formulated, and includes a rotary wafer switch which is used
to select either one or two of the sixteen second-local-oscillator
crystals present on each assembly. In addition, this assembly
includes a. switch to permit operation with one crystal, or with
any two adjacent crystals; and a switch to gate the desired r-f
head. Construction of the first breadboard model has begun.
Prototype models are scheduled to be completed on 15 September
1956.
7-1. During the coming report period, the major effort will be
directed toward the following objectives:
a. completion of development work on System 3 -- The
principal task, here, is to reduce spurious responses.
b. production of the initial two deliverable systems
c. completion of the first deliverable System 3 test set
d. completion of the pre-prototype breadboard model of
System 3.A
e. completion of all flight testing
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 Approved FoRelease 2c5 MAN DP8160087000300060019-8
Preliminary Tests of System 3 Cooling
System 3 (and 3A) is provided with essentially two distinct means
of cooling which may be described as follows:
a. A method in which the dominant heat transfer is by
more or less continuous conduction through metal paths
extending from the heat producing components to the
outer skin structure of the aircraft -- The heat
transfer from the skin is, of course, by convection to
the atmosphere, which is the ultimate sink. This
method will be used during normal flight operation of
the receiver.
b. A method in which the dominent heat transfer is by
forced air convection effected by means of a portable
blower -- By means of suitable rubber hose connections,
the space within the top cover is pressurized by the air
delivered from the blower. The cover serves as a
plenum chamber to distribute the cooling air which
passes through the chassis and over the components.
The air is then discharged through a suitable opening
in the bottom cover. This system is to be used during
ground checking of the receiver in the aircraft, and
during bench servicing.
The two systems described have been given preliminary field
tests in the type C-47 laboratory airplane. A summary
tabulation of the results appears below and these appear to be
satisfactory. Inasmuch as under actual flight conditions, skin
temperatures are expected to be 50 to 60 degrees Centigrade
less than the results show, the various component temperatures
observed will be reduced by a like amount. For this reason, a
column of corrected values, based on this fact, is listed.
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 Approved For Release 20f RETP81 B00878RP00300060019-8
Test results clearly indicate that the blower has ample capacity
to permit the System to operate safely under severe conditions
of altitude (of the base site), air, temperature, and dust.
Temperatures corrected for a high-elevation base site on a
very hot summer day, are given. The assumed conditions are
also indicated.
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 Approved Fa please SIC RETDP81 800870000300060019-8
Item
Location of Thermocouple(s)
T
Terminal (Equilibrium) Temperature
Degrees Centigrade
As Observed
Corrected to
t'mated actual
Ili lht conditions
1
Center of main chassis plate
89
37
2
Tube shield of second local-
oscillator assembly
109
57
3
Tube shield of third local-
oscillator assembly
104
52
4
Resistor shield of third local-
oscillator assembly
107
55
5
Tube flange of preamplifier
71
19
6
Tube shield of i~-f assembly
98
46
7
Tube shield of r-f assembly,
bands 3, 5, 8
80
28
8
Power supply rectifiers
62
10
9
Power supply chokes and
transformer
68
16
10
Aircraft skin adjacent to
receiver
32
-20
11
Edge (flange) of chassis
plate
48
-4
Notes on above summary:
The receiver was mounted in box bracket similar to the bracket to be used
in the operational aircraft. The material was 1/8 inch thick 2S aluminum
alloy mounted in a fuselage window cut out in the skin so as to be directly
exposed to the slip stream.
The corrections are based on an assumed skin temperature of minus 200C
as indicated by item 10.
SECRET C
Test Results of
The Conductive Method of Cooling
(Cooling During Flight)
Date: June 13, 1956 Time: 1700 to 1930 (approximately)
Flight: South from Los Angeles, California, to approximately
25 miles north of San Diego, California, and return
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 Approved Foa= R lease 20 DP81 B00878 00300060019-8
Test Results of
Blower Cooling
(Forced-Air Cooling During Ground Tests)
Date: July 3, 1956 Time: 1100 to 1230 (approximately)
Place: C-47 test airplane at Los Angeles
Item
Location of Thermocouple(s)
Terminal (E uil:ibrium Tem erature
Degrees Centigrade
As Observed
Corrected as
noted below
1
Center of main chassis plate
40
76
2
Tube shield of second local-
oscillator assembly
45
81
3
Tube shield of third local-
oscillator assembly
43
69
4
Resistor shield of third
local-oscillator assembly
50
76
5
Air of i-f assembly
41
77
6
Tube shield of i-f assembly
45
81
7
Aircraft skin adjacent to
receiver
34
70
8
Edge (flange) of chassis plate
36
72
9
Air inlet to blower
27
49
10
Air discharge from blower
41
67
11
Mean rise through blower
and receiver
14
18
Notes on above summary:
The corrected temperature values are based on the following assumptions:
a. An altitude at test site of 5000 feet above sea level.
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 Approved For Re ease 200SEC-RETP81 B00878R 00300060019-8
b. An atmospheric (hence blower air inlet) temperature
of 49?C (120?F) .
c. Test is conducted in shade under awning or other similar
structure thereby eliminating sun load. It should be noted, however,
that with the aircraft in strong sunlight, the corrected terminal
temperatures would probably be increased by less than three degrees
centigrade.
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