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CIA NRP EC URS-1 →
An EC device
is a covert listening device (bug)
of a passive nature,
which means that it is powered by a strong RF signal that is transmitted
from the listening post. In CIA/NRP terminology, such a device was known
as a passive element or PE.
Both the activation signal and the PE operated in the 370-390 MHz band,
which means that in a two-antenna system at the listening post, the antennas
had to be separated as far as possible, and sufficient spillover attenuation
is necessary. In a single antenna system this attenuation is generally
provided by the antenna's duplex unit.
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As the PE is powered by a remote RF signal, it operates at a very low
power and transmits a very weak signal in the order of 100 µW. To guarantee a
proper reception of this weak signal at the LP, it was important to carry
out a site survey with the TEC, prior to installation of the PE,
preferably at the actual target site.
Note that the path attenuation or path loss is applicable
twice: once on the high-power activation signal from the LP to the PE,
and once on the PE signal back to the LP.
TEC was intended for studies on the propagation of radio signals over
an obstructed path, but was also considered a valuable tool for training
CIA technicians when preparing for an operation.
Based on the way the board of the unit's internal receiver is built,
all TEC units were hand-made.
As the device shown here is marked as Mark II, we assume it was the
successor to an earlier one.
In 1977, the TEC Mk II was succeeded
by the more advanced URS-1 path loss survey system.
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The receiver is the largest part of the survey system. It is fully
self-contained and is housed in a blue metal enclosure, with all controls
and connections at the largest surface (front).
The receiver is powered by a Mallory TR-135R 6.75V
battery 1 that should be installed in a slot at the right.
An adjustable neck strap
is provided to allow the receiver to be operated with both hands free.
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The interior of the receiver can be accessed by removing the non-recessed
screws from the edges of the front panel and removing the lid of the
battery compartment at the right. The front panel
can now be removed from the case shell.
All internal parts and sub-assemblies are mounted to the
inside of the front panel,
as shown in the image on the right. The rectangular blue box
at the top left holds the IF and AF stages of the receiver.
The RF stage, the local oscillator (LO) and the mixer are mounted in the
rectangluar aluminum unit at the front left.
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The remaining space is taken by the controls, the
battery holder and
the dB-meter. In the above image, the lid of the IF/AF section has been
removed in order to show the circuit board.
Judging from the
manufacturing method
of this circuit board, each TEC unit was completely hand-made.
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This was an industrial stacked mercury battery, that was also used
in military equipment, where it was known NSN 6135-00-801-0587.
Mercury batteries are illegal for domestic use today.
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A small handheld transmitter
is provided as an RF energy source for performing calibrated
path loss measurements. It produces just 100 µW of RF energy
and is powered by a Mallory TR153R 4.05V battery that is
installed at the bottom.
The entire solution is built inside
one half of a ½λ dipole antenna
and weights just 100 grams. The transmitter operates in the
370 to 390 MHz range and can be modulated with a 1500 Hz tone.
The frequency can be adjusted by means of a
slider
that is located close to the feed point.
The design is similar to an
EC target element.
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The installation was supplied with a reference antenna that should be
connected to the TEC receiver.
The antenna consists of a 300 Ω
½λ folded dipole, with a 90° corner reflector.
The antenna could be fitted on a
tripod or held in the hand using the
supplied grip, which is actually a modified
screwdriver.
The hinged relector could be folded in such a way that the entire antenna
could be stored on top of the receiver
when the installation was in transit.
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AF
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Audio Frequency
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CIA
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Central Intelligence Agency
United Status intelligence agency.
➤ More
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EC
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Easy Chair
CIA codename for the super-secret project to develop covert listening devices
based on the principle of the
Russian resonant cavity microphone,
also known as The Thing.
The name EASY CHAIR is also written as EASYCHAIR.
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IF
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Intermediate Frequency
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LP
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Listening Post
Common expression for the monitoring station. In the case of a PE, this
is also the position of the activation transmitter.
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NRP
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Nederlands Radar Proefstation
Dutch Radar Laboratory, at the time located in Noordwijk (Netherlands).
➤ More
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PE
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Passive Element
NRP name for derivatives of the resonant cavity microphone.
In this sense, passive means that it does not have its own local
power source.
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RF
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Radio frequency
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TEC
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Test Easy Chair
Test equipment for Easy Chair installation.
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- Manual for TEC - Mk II
14 June 1963.
- Operating Manual - TEC Mk I
Date unknown.
- Technical Manual - TEC Mk I
Date unknown.
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- Anonymous, TEC Mk II survey receiver
July 2016.
- NRP/CIA, Collection of documents related to TEC
Crypto Museum Archive, CM302457 (see above).
- Wikipedia, Corner reflector antenna
Retrieved January 2017.
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© Crypto Museum. Created: Wednesday 04 January 2017. Last changed: Monday, 26 December 2022 - 12:19 CET.
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