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Spy radio set
The SP-15 is a complete radio station that was developed in Germany
in the early 1960s by Wandel & Goltermann for the
Bundes Nachrichtendienst (BND). It was intended for agents,
special forces (SF) and stay-behind organisations
(Gladio).
Certain components of the SP-15 radio station were also used by the
organisations of other countries.
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A complete SP-15 radio station consisted of a receiver (FE-8),
a transmitter (FS-7),
a burst encoder (RT-3), an AC mains power supply unit
a 12V battery power supply unit, various battery chargers and a box
with various accessories, spare parts and tools.
The image on the right shows the transmitter (left), the burst encoder
(front), the 12V battery PSU (right, bottom) and the receiver (right, top).
Different configurations of the SP-15 were used in other countries
(see below).
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For use by agents, the radio set was usually packed in a leather
suitcase. For the Special Forces a special webbing unit
was available, allowing the units to be carried on the chest.
When used by stay-behind organisations (Gladio) the various units were
usually stored in a water tight container.
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The receiver was developed by the German manufacturer Wandel &
Golterman (W&G) in 1958 and was given the designator BN-58.
W&G is widely known for the production of high-end electronic test
equipment such as audio and HF spectrum analyzers.
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The BN-58 is one of the first small receivers that was completely
transistor-based. It featured very low power consumption.
The double conversion superheterodyne receiver has an IF of 1.635 MHz
and covers 2.5-24MHz divided over two ranges.
This receiver was used again in the late-1970s, with the newer
SP-20 spy set.
 More information
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Transmitter FS-7 (FSS-7, BN-22)
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The transmitter of the SP-15 was developed by Pfitzner
in Germany and was called FS-7.
It has two valves (EL95 for the oscillator and EL81 for the HF power amplifier)
and one transistor (OC450) and is suitable for CW (A1, morse) only.
The transmitter is also known as BN-22.
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Maximum power output was 10W or 20W, switchable from the PSU (see below).
The transmitter is crystal operated and the frequency is determined by a quartz
crystal which is inserted in a socket on the front left of the unit.
Some units were later modified for use with an external synthesizer
(see below).
As the transmitter does not produce a tone when sending morse, the morse
key can be connected to the transmitter and the receiver simultaneously.
For this purpose, the receiver has a so-called side-tone input
at the rear.
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The transmitter covers 2.5-24MHz in 6 colour-coded ranges.
The 4 knobs at the front of the unit each have a differently coloured arrow
and a table on top of the unit is used to determine the settings for each
frequency range:
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- 2.5 - 3 MHz (orange)
- 3 - 4 MHz (blue)
- 4 - 5 MHz (yellow)
- 5 - 8 MHz (green)
- 8 - 14 MHz (red)
- 14 - 24 MHz (brown)
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The images below give a good impression of the build-quality of the
transmitter. Both valves are clearly visible and the last image shows the
circuit diagram that is found inside the lid.
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A morse key (or keying device) can be connected to the transmitter in two
different ways. The standard method is shown in the leftmost drawing below.
It is suitable for speeds up to 100 baud. In this mode a transistor (OC450)
is used for switching the cathode of the oscillator (EL95), whilst the PA (EL81)
keeps running. A side-tone signal is available for the receiver (using the
supplied T-connector).
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Connection of a manual key (left) or the RT-3 burst encoder (right)
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When using the RT-3, however, a different connection should be made in the
5-pin DIN plug. As a result, the oscillator is kept running, whilst the
screen-grid voltage of the PA (EL81) is switched by the RT-3. This allows
speeds up to approx. 800 baud.
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The SP-15 came with a large number of accessories, some of which are
shown here.
The most remarkable one is the surprisingly cheap looking morse key,
made of a rather poor quality plastic.
In use, the key is not as bad as it looks as it's rather heavy.
Furthermore, the plastic is shielded on the inside.
Other accessories include antennas and cables.
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Help requested: There is one particular item found with an SP-15
radio set, of which the precise purpose is still unclear.
The unit shown in image #5 below,
fits the crystal socket of the FS-7 transmitter. The crystal itself
can be plugged into a socket on the unit. A rotatable knob at the front
of the unit is probably used to tune the crystal. And then there is a
piece of shielded cable that has no connector at the other end...
If you know what this is, please contact us.
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Two different versions of the DC power supply unit were available
(12V and 24V) but only one of these was supplied with the SP-15
radio station.
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The version shown here is for use with 12V batteries, e.g. as used
in a car. It contains a power inverter with a fairly small transformer
and two PNP Germanium power transistors (AUY22, AD105 or TF90).
The power supply was used to set the maximum output power of the
transmitter. A switch at the front panel allowed selection between
20W and 10W (i.e. full and half power).
The pictures below give a good view of the interior of the PSU.
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A relay was used to prevent the unit from being connected the wrong way
around. The circuit diagram is glued inside the lid. At full power,
the PSU would draw approx. 8A from the battery.
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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-15.
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-15 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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For use by special forces and reconnaissance units, a special webbing
pack was developed that allowed the various units to be worn on the
chest. The webbing pack had a pocket for the transmitter and power
convertor and another one for the receiver and the accessories.
Power for the set was delivered by a separate (heavy) battery belt
that would be worn around the waist.
The belt contained 10 rechargeable NiCd batteries of 1.2V/10Ah each.
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SP-15 with Synthesizer (Dutch Gladio)
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In the Netherlands, the SP-15 was used for the local stay-behind
organsiation O&I (Operatiën en Inlichtingen) during the 1960s
and 1970s.
O&I agents were given a water tight container that contained
the SP-15 radio set, together with a wide range of accessories
such as antennas, spare parts and a burst encoder (see above).
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Most Dutch SP-15 sets have been destroyed in the early 1990s, when
much of the Dutch stay-behind organisation was dismantled. Only two
complete sets are known to have survived. One is on plublic display
in the Royal Dutch Signals Museum and the other one was shown in
the special exhibition Secret Messages
in Museum Jan Corver in 2008, where we were able to have a closer
look.
The image on the right shows the green water tight container and some
of its content. Note the additional syntesizer unit at the right.
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It is likely that the transmitter initially was crystal-driven, just
like the German SP-15, but that it was later converted for use with
an external synthesizer. Evidence has been found in the Dutch National
Archives, that the synthesizer was added in the mid-1970s.
A complete set consisted of the following items:
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As explained above, the transmitter was modified at some point for use
with an external synthesizer. The standard transmitter (FS-7) has a socket
for a crystal on the front left of the unit.
The image above shows a modified transmitter of which the crystal
socket is removed and closed with a small aluminium plate, held in place
by two small bolts. The modified transmitter was designated FSS-7
(Frequenz Synthesizer Sender).
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The connections of the socket on the left of the unit
have been modified in order to support the external synthesizer.
A small black interface box (IFS-7) was added in between the PSU and the
transmitter, and the new synthesizer was connected to the front of it.
The image on the left shows the complete setup.
The morse key, or the burst encoder, was connected to the black box
as well, rather than directly to the transmitter.
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The IFS-7 (black box) also had a built-in calibrator and a crystal socket
at the front, allowing the old crystals to be used instead of the new
synthesizer.
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Most of the Dutch SP-15 radio stations were equipped with the
Speicher burst encoder.
More information
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Inside the container were two grey boxes with tools and accessories.
Each box was closed with a canvas strap to avoid the contents falling out.
Inside the boxes were the standard tools, such as srewdriver and pliers.
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Various adapters were supplied to allow connection to a variety of mains
(lamp) sockets. Two wire antennas were supplied, one for the receiver and
one for the transmitter, the latter being of the roll-up type (visible in
the image on the right).
Other accessories were earphones, fuses, insulators, test cables, audio
cables, insulation tape, earth (ground) connectors and a rechargeable
pocket light.
Detailed images below.
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© Copyright 2009-2011, Paul Reuvers & Marc Simons. Last changed: Wed,31 Aug 2011.11:46:43
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