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Early radio bug
At the height of the Cold War, the
Russian Intelligence Agency (KGB)
used a variety of methods and equipment for eavesdropping on conversations
in hotel rooms, embassies, private homes, etc. The device shown below
was made around 1964 and was one of the first transistorized bugs.
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The image on the right show the Russian KGB bug.
The device measures 75 x 23 x 10 mm and is housed in a metal enclosure.
It has three contact pins to which the power supply and the antenna are
connected. The large black circle at the left is front of the
crystal microphone.
The electronic circuit
is extremely simple and consists of just one
(Germanium) transistor, a simple coil and a couple of passive components.
The resonance circuit
consists of an adjustable coil with four windings,
and a large capacitive (crystal) microphone connected in parallel.
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As the bug is based on a free-running oscillator, it is rather unstable
and sensitive to power variations. In order to avoid the so-called
hand effect, the transmitter is built inside a
metal enclosure.
Furthermore, the frequency is adjusted by moving a (grounded) core
towards the coil. As this core is grounded, a normal screwdriver can
be used for the frequency adjustement
at the side of the unit.
The adjustment can be locked by means of another screw that is located
at the top surface. Power is connected to the
two-pin terminal
at one of the short sides (right).
When picking up a conversation, the capacity of the crystal microphone
will vary slightly, causing variations in the frequency of the resonance
circuit. This will effectively result in a Frequency Modulated (FM) signal.
The KGB bug shown here was ideally suited for a wide variety of concealments,
such as a piece of furniture (e.g. the leg of a table)
or a decorative table piece. An external power source (e.g. a battery) was
connected to the 2-pin terminal
at the right, while a wire antenna was
connected to the single terminal
at the opposite side (above the microphone).
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 01 February 2014 - 09:46 CET
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