← Easy Chair
It is intended for checking transmitters (bugs) that operate in the
235 to 325 MHz frequency band and feature a 22 kHz or 40 kHz
subcarrier. It can perform a variety of tests and
provides several internal signals for further analysis.
The device is basically a low sensitivity receiver. Devices under test
can be connected directly to the input of the UVK-153, or can be placed
in its vicinity, in which case a ¼λ whip antenna should be
connected to the input socket. The device is housed in a metal
grey hamerite enclosure with a leather grip and a metal lid to cover
A prototype of the transmitter tester was released for evaluation in April
1981, together with preliminary handwritten instructions [A]. Based on
feedback from the CIA, the tester was further improved over the course of
the following years and was made compatibile with other CIA
This resulted in the final version that was introduced in 1984 [B].
The UVK-153 is housed in a
strong metal enclosure
that can be carried by the leather handle at one of the sides.
A removable cover
protects the controls and connections against dust and damage.
The device is usually placed horizontally on a desk and is
operated by internal batteries
that are installed in a
removable compartment at the top.
Six 1.5V AA-size batteries are required.
When testing a bug, it should be connected to the RF HIGH input
at the top left. Alternatively, a whip antenna can be installed at the
RF LOW input, whilst the transmitter is placed in its vicinity. The large
tuning knob should be set to the approximate frequency of the transmitter.
Next, the desired measurement
should be selected with the
function selector at the right.
Most tests can be performed with the
but all the relevant signals are available at the
lower edge for
further analysis by external test equipment, such as a frequency
counter and an oscilloscope.
- RF HIGH
Input for RF signals with a level between -15 and +15 dBm.
Primary used for closed circuit measurements, in which the
RF output of the transmitter is connected directly to the UVK-153.
- RF LOW
Input for RF signals with a level between -40 and -10 dBm.
Primarily used for short range air path measurements, in which the
¼λ whip antenna is used and the transmitter is placed in the
vicinity of the UVK-153.
- MON VIDEO
Shows the combined baseband noise and subcarier modulation, passed
through a 100 kHz low-pass bandwidth filter. Use an oscilloscope to
check the shape of the signal, which can be sinusoidal, trangular
or square wave.
- MON BASE
Shows the baseband noise within a low-pass bandwidth of 5 kHz, allowing
judgement of whether the noise is random, clipped, or has a (too) high
- MON SUB
Provides the filtered subcarrier modulation, either in a 15-30 kHz
bandwidth, or in a 30-50 kHz bandwidth, subject to the setting of the
22-40 switch. Allows exact measurement of the subcarrier frequency
by means of an external frequency counter.
- MON AUDIO
The recovered audio is available on this socket, allowing measurement
of SINAD, noise floor, or audio level compression, in conjunction
with external test equipment.
Standard 6.3 mm jack socket for a common 600Ω pair of
headphones with a PL55 connector. Allows monitoring of the demodulated
audio signal. The level can be adjusted with the PH LEVEL knob.
Indication of RF input level on the meter, in conjunction with the
continuous LEVEL adjustment knob. Operates only when the local
oscillator is tuned to within 10 MHz of the transmitter's
RF frequency. With the LEVEL adjustment fully clockwise, the meter
should show a more than midscale reading.
- FIF x1.0 MHz
The meter shows the difference between the transmitter's frequency (TX)
and the frequency of the local oscillator (LO). A midscale reading is
recommended during a test, which means that the LO is tuned 5 MHz
lower than the TX frequency. Can also be used to check frequency
deviation during pulling or pushing, also known as the
- ΔFSUB x10 kHz
The meter shows the transmitter peak RF excursion caused by subcarrier
modulation. A full-scale reading represents 100 kHz excursion.
- ΔFBASE x10 kHz
The meter shows the transmitter RF excursion caused by baseband noise
modulation. Note that the meter shows the average noise
voltage. A full-scale reading represents 100 kHz average
- FSUB x5 kHz
The meter shows the actual subcarrier frequency of the transmitter.
A full-scale reading represents a 50 kHz subcarrier frequency.
For a more accurate measurement of the subcarrier frequency,
a frequency counter should be connected to the MON SUB socket.
- ΔFAUDIO x1 kHz
The meter shows the frequency excursion of the subcarrier caused
by audio modulation. A full-scale reading represents a 10 kHz
The UVK-153 is known to be suitable for testing the following CIA bugs:
The block diagram below shows the basic operation of the UVK-153.
At the left are the RF inputs, of which one is an attenuated version
of the other. The latter is used for direct connection of a transmitter.
The signal first passes a band filter, and is then mixed with the
variable signal from the local oscillator (LO), into a 10 MHz wide IF
signal with its center frequency at 5 MHz.
The IF converts the signal into 0 - 150 kHz that is further processed
in the video circuitry and eventually the audio circuitry that reproduces
the original audio. At various stages, the signals from the IF, Video and
Audio stages are available on BNC sockets, for further external analysis.
The device is housed in a
metal grey hamerite case, that had formerly
been used as storage box for Russian multimeters and transistor testers.
The case measures 23 x 16.5 x 9.5 cm and was professionally modified for the
current task. They were probably obtained from a surplus store.
The interior of the UVK-153
consist of a double-sided
high-quality printed circuit board (PCB)
that is mounted to the rear of the control panel.
The PCB contains all electronic components, with the exception of the tuner,
which is housed in a
separate fully shielded case
that is mounted between the PCB and the battery compartment.
The image on the right shows a detail of the PCB with its first-class
components. From the images it should be evident that the UVK-153 was not
a quick-and-dirty bodge, but rather a professional test device used
for verification and alignment.
The front panel, with the electronic parts mounted to its rear side,
fits snugly inside the Russian case, and is fixated with four screws
at the edges of the control panel. The battery block should be
into the empty space above the control panel and is guided
by two vertical stubs.
- Concise Operating Instructions for Transmitter Tester
NRP, 23 April 1981. CM302627/K.
➤ follow up 26 August 1981
- Operation and Test Manual for UVK-153 Transmitter Tester
NRP, August 1984. CM302627/S.
- Environmental Test Report on UVK-153 Transmitter Tester
NRP, January 1985. CM302627/T.
- NRP/CIA, Collection of documents related to SRS-153
Crypto Museum Archive, CM302627 (see above).
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© Crypto Museum. Created: Thursday 18 May 2017. Last changed: Tuesday, 16 January 2018 - 15:25 CET.