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Spy radio set
The SP-20 was developed in the late-1970s in Germany by Pfitzner and
AEG Telefunken
as a replacement for the aging valve-vased SP-15.
It was used as a true spy radio set that was used by a number of
Stay-Behind Organizations in Europe (Gladio)
as well as by the Special Forces of the German Army.
The two versions can be determined by their colour, but are
otherwise identical.
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The SP-20 consisted of a transmitter, an antenna tuner, a receiver, a synthesizer
and accessories.
Messages were transmitted in
morse code by means of a manual key or
a burst encoder.
Various burst encoders have been used with it.
The image on the right shows the military version of the SP-20 that was
used by German Special Forces (SF). All units are painted in the standard
NATO olive green colour.
It is shown here with the RT-3 burst encoder.
The version used by stay-behind (Gladio)
was grey and was used with a variety of morse burst encoders.
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Most SP-20 units have been found without a matching receiver.
Although the manufacturer developed a digital receiver for the
SP-20, only a limited quantity was built and it was never put into
large scale production. Instead the old FE-8 receiver,
that was supplied with the SP-15 spy set, was used.
All units are housed in a similar case of approx. 155 x 105 x 32 mm,
except for the (older) FE-8 receiver (see below). A similar case
was later used for the Speicher burst encoder.
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The S-6800 transmitter was developed by AEG Telefunken and is fully
transistorised.
It is both crystal and synthesizer operated and is suitable for
CW (morse) and FSK (frequency shift keying). The maximum ouput power
is 25W.
Note the two rigs on top of the unit, allowing it to be attached to
the ASG-6800 antenna tuner (see below).
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The ASG-6800 antenna tuner was designed for use in combination with the
S-6800 transmitter. Like the transmitter, it was manufactured by AEG Telefunken
in the mid 1970s (1975-1977).
The tuner was connected to the transmitter by means of a short coaxial
cable with an SMB-connector at both ends.
At the bottom it has two rigs that allows it to be slotted onto the
S-6800 transmitter (see above).
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Initially, the S-6800 transmitter was crystal operated. Later, an external
synthesizer unit (KS-30) was developed by Pfitzner. This was probably
early in 1983.
It was added to all existing SP-20 stations and connected to the transmitter
via a multi-pin connector on the left. A rather long cable was supplied to
connect the KS-30 to the S-6800.
The sythesizer allows a frequency coverage of 2-24MHz in steps of 1kHz.
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The SP-20 radio set in the above image is shown without a receiver.
Although a suitable digital receiver, in a similar case, was developed
by Pfitzner, it was never put into production.
Instead, the FE-8
receiver of the older SP-15 (1958)
spy set was used.
 More information
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Each SP-20 unit came with a set of spare parts, tools and accessories.
In most cases, these were packed in a sturdy 'lunch box' with a canvas
strap to prevent the contents from falling out.
The image on the right shows an example of such a toolbox. It contains
a screwdriver, pliers, insulation tape, ceramic antenna insulators, etc.
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The antenna tuner makes it possible to use virtually any type of antenna
with the S-8600 transmitter. In practice, a long antenna wire was used on most
occasions. The antenna, and a suitable ground, are connected to the left
side of the tuner, via 2 banana-type sockets.
The images below show some of the typical wire antennas that were supplied
with the SP-20. Please note that transmitter and receiver each needed a separate
antenna.
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The SP-20 was also used by German Special Forces. The military version
of the spy set was housed in olive-green cases and could be worn on the body
by using a special canvas webbing kit with two plastic cases, as shown
in the image on the right.
Each plastic case had two pockets, allowing all units of the spy set to
be transported easily. The plastic cases could be attached to a canvas
waist belt, which was held in place by suitable shoulder straps.
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In order to minimise the risk of detection during a transmission,
a burst encoder was often used in combination with the SP-20.
The burst encoder allowed a pre-recorded message to be played back
at very hight speed, so that the transmission was kept as short as
possible.
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The first burst encoder to be issued with the SP-20 was this
electro-mechanical RT-3 unit.
A small military-grade metal box that allowed a message of
25 characters to be stored mechanically. Once on-air, the message
was played back by operating a hand crank.
Later, more advanced burst encoders were issued, such as the
GRA-71,
MMP
and Speicher.
More information
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The Speicher (Eng: memory) was a fully electronic burst encoder
for sending numbers at high speed in morse code. It was powered
directly from the mains and was housed in a similar case as the
SP-20 spy radio set.
The Speicher was probably issued in the 1970s to replace the
rather limited RT-3.
Eventually it was replaced itself by the
more advanced MMP.
More information
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The MMP was a fully electronic high-speed (1200 baud) burst
encoder that was used with both the
SP-15 and the SP-20 spy sets.
The MMP replaced older devices, such as the mechanical
RT-3,
the American AN/GRA-71
and the early electronic Speicher.
It could hold more than 1000 letters and numbers in its battery-bakced
CMOS memory and send them at various speeds between 15 and 1200 baud.
More information
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Monday, 01 April 2013 - 08:17 CET
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