Thermocouples and Meters in the TAC-1 Antenna Tower

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-02820A000300020006-0
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 4
• Document Creation Date: December 9, 2016
• Document Release Date: May 18, 2001
• Sequence Number: 6
• Publication Date: September 16, 1957
• Content Type: MF

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:24ORIL FOR THE FILE
it September 1957
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ABJECT: Thermocouples a in the TAC-1 Antenna Tumor
7EFEREHGE1 FEB 7-13P:
with regard to the referenced memorandum, the investigation of the
cause (a) of burned out thermocouples and meters was picked up as a
project. The following report contains the suspected causes of this
trouble and the results of the investigation.
About 15 August Masers. visited
the local reprtimo.resezief}on for
this visit was to get their comments on a burned-out thermocouple we
had with us and to find out if they had experienced any stmiler troubles
on these parts. Their answer was negative; they have bad no trouble
with either the thermocouples or meters:. These parts, they stetted, are
being used in many applications and without complaints of any sort. we
left the damaged thermocouple with them for factory inspection and repair.
On 1 August four new thermocouples and two meters were requisitioned
from stock to be used in the following test:
a) Determine if the thermocouples are wired correctly.
h) Check on the accuracy of the meters and thermocouples.
Check on the reeonant or parasitic circuits in the TAC-1
meter circuit.
d) Check on possible FP rectification in the meter circuit.
e) Test the ample tera and thermocouples in the TAC-1
for proper or improper operation if possible.
This investigation took place at the T&I Section, and
the results of the above test were indicative of good quality meters and
thermocouples, correctly wired in the circuits. There was no indication
of parasitics or faulty design of the TAC-1. Since the referenced memo-.
reed= suggest6many possible solutions to the problem, esch will be used
as a guide to expand the following points:
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The connections to the thermocouple were changed to provide
all possible combinations. Only one way is correct and this is
the way it is wired into the circuit.
" 11'
ensured us, and it was checked and found correct,
that only a slight inaccuracy of the meter would result in horizontal
versus vertical mounting of the thermocouples.
:_taasta.
The referenced morandum is correct insofar as using 600 ohms
.there the resistance in concerned. Hoeever, under certain conditions
the impedance of the tranymiesion line may he much higher OR lower.
Considering a 50 ohm line terminated correctly, and Pe 12S) 9 x 50
or 450 watts 3 amperes. Sow if the resistance were lower, the
indicated nower would be less at the same current, but since the
resistance is less, more current would flow, perhaps resulting in
a burned out thermocouple at say, 40 ohms.
Through use, it was found that the 3 ampere meter used in the
TPC-1 is a good Tait*. When tuning the TAC-1 a current reading of
one ampere is not uncomeon and at time this meter is very helpful
in tuning. Therefore, if a larger meter were used, say a 5 or 10
ampere meter, the indication on the larger eater may be too slight
to be any help while tuning with these lower currents. Zoom of the
values of the currents encountered are higher than 5 Inverse; pre-
cluding the installation of a 5 ampere meter eaaa so far nothing over
10 amperes has been noted.
P-4
the TAC-1 can handle impedance variatioa over 20 to 1,
it would be far better to adjust the antenna or transmission line
for s more correct match than to widen this impedance range of the
7PC-1 or increase its capacity by a further 1,-C combination. In
essence; what is outside the range of the TAC-1 should be brought
,)lore close, not increase the range of the TAC-1.
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V. 6
It is felt that the instruction
Teotjon II of the manual explains the
with a email amount of operating time,
able to adjust the TAC-1 with a minimum of
fashion. Perhaps it would be sufficient to
nett') its variable coupling and the tapped
sat up correctly on a very few settings but vi
to provide a smooth response when going through resonance. An
operator, with a minimum of time and the present instruction book,
should have no difficulty tuning the TAC-1 with a decent load. When
the load is highly reactive and outside the range of the TAC-1 no
further instruction would be of help.
TAC-1 is adequate.
nne tuners and
should readily
in the correct
hat the TAC-17
troll, can be
variation
la.12,Likutz.
It wee found that when operating the T
three ampere current reading, when the output
to a decent load (500 watt light bulb) the current was not aboo
high. It may be that when the operator finds himself reading a cur-
rent of three amperes with the transmitter on Talt and not in a
position to be able to construct a new antenna or correct the one
used, a thermocouple shunt would be in order. For this shunt, unless
remotely controlled, an extension of the RF leads to the thermocouple
ram a suitable switch would have to be made. A casual inspection
of the compactness sad general construction of the TAC-1 points up
he fact that it may be difficult to insert a shunt even though this
appears to be the most logical solution of operation with a high
current.
Conc?luNion
The TAC-1 a well designed equipeout
outlined in the instruction book. Opera
at a MitlinUM for this type of equipment and no
experienced by the operators to cause them to burn out
couples or meters by improper use. The meters and thermocou,
of high quality, accurate and are correctly wired in the eircuit.
A higher capacity meter would have to be in the order to 10 amperes
and this would preclude the use of same when tuning with the low
currents of one ampere or so. Good engineering practice would dictate
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the use of a better matched antenna and transmission line when
abnormal currents are present. Further, when experiencing these
abnormal currents, it should be pointed out that such a mismatch
to cause this trouble indicated:a very inefficient antenna and trans-
mission line system. However, when the antenna or tranamievion line
cannot be changed a thermocouple shunt seems to be the only solution..
6 of the project will be to undertake a study of the
mechanical construction of the TAC-1 with the ides of incorporating
a. shunt. If this proves feasible, a modification work order- will
be mAde.
Distribution:
Orig. & 1 - RES File
1 71 Off/Sli
V"-- Monthly Report
1 - RES Chrono
00-E
Inc/111111111111m0/E0U
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