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SP-15   FSS-7
German spy radio set

The SP-15 is a self-contained modular spy radio station, developed around 1958 by the German Intelligence Service – Bundes­achrichten­dienst (BND) – and manufactured by Wandel & Goltermann. It was intended for espionage, diplomatic radio traffic, Special Forces (SF), clandestine or covert operations and Stay-Behind Organisations (SBO). Certain components of the SP-15 radio station were also used by partner organizations and agencies in other countries. In The Netherlands the SP-15 was also known as FSS-7 1 , which was actually the name of the valve-based transmitter.

A complete SP-15 radio station consisted of an FE-8 receiver, an FSS-7 transmitter, a burst encoder, such as the RT-3 or the GRA-71, 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 (right), the DC PSU (centre), the receiver (left), a morse key (front right) and various accessories. The set was often supplied with a burst encoder for high-speed transmissions in morse code, to minimize the chance of direction finding (RDF).
  
Typical SP-15 spy radio outfit

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 organizations (SBO) the various units were commonly stored in a metal container. The SP-15 was suitable for deployment anywhere in the world. It was also used by the US Central Intelligence Agency (CIA), for example in covert operations in the former DDR (East Germany) [7].

Around 1970, the SP-15 was succeeded by the SP-20 developed by Telefunken, but remained in use in some countries well into the 1980s. In The Netherlands, for example, the SP-15 was used until it was replaced in the mid-1980s by the digital RACAL PRM-4150. Eventually, all SP-15 units – in fact all clandestine sets in Europe – were replaced by the pan-European FS-5000 (Harpoon).

  1. The SP-15 or the FSS-7 transmitter, is sometime erroneously referred to as FS-7 or FFS-7.

SP-15 spy radio set Typical SP-15 spy radio station Typical SP-15 spy radio outfit Crystal operated transmitter
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SP-15 spy radio set
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Typical SP-15 spy radio station
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Typical SP-15 spy radio outfit
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Crystal operated transmitter

Available parts
Valve-based FSS-7 transmitter made by Wandel & Goltermann, also known as BN-22
TX
FE-8 receiver made by Wandel & Goltermann, also known as BN-58
RX
Alternative FE-9 receiver made by Wandel & Goltermann, also known as BN-48 or UHU
UHU
Mains AC power supply unit
AC
DC Power Supply Unit (12-24V)
DC
Various types of burst encoders Accessories and spare parts Dutch stay-behind (Gladio) outfit
NL
Special Forces webbing kit FSK Modulator for very high speed burst transmissions
FSK
Calibrator for the receiver
Cal
Transmitter   FSS-7 · BN-22
The transmitter of the SP-15 was developed by the Bundesnachrichtendienst (BND) around 1958 and manufactured by Wandel & Golterman (W&G) until 1962. In Germany it was known as FSS-7 or BN-22. It has two valves (EL95 for the oscillator and EL81 for the HF power amplifier) and one transistor (OC450) and is suitable for CW only.

Power output was 10W or 20W, switchable from the PSU (see below). The transmitter is crystal operated, but the Dutch version (FSS-7/NL) was later modified for use with a synthesizer.

 More information

  

Receiver   FE-8 · BN-58
The FE-8 receiver was developed around 1958 by the Bundesnachrichtendienst (BND) and was manufactured by Wandel & Golterman (W&G). It can be used in combination with the FSS-7, but also as a standalone receiver. Power is provided by an internal battery, or by an external source.

The receiver has two ranges (2.5-9.1 MHz and 9.1-24 MHz) with permeability tuning, resulting in a linear scale for both ranges. This receiver was also used with the later SP-20 radio sets.

 More information

  
FE-8 (BN-58) receiver

Receiver UHU   FE-9 · BN-48
For situations where the wide frequency range of the FE-8 was not needed, the smaller FE-9 was used, which covers the lower frequencies only (2-9 MHz). The reduced size and weight made it easier to smuggle the device into a country.

The FE-9 (codenamed UHU) is suitable for the reception of AM and CW (morse) signals. It was developed by the Bundesnachrichtendienst (BND) and built by Wandel & Golterman (W&G).

 More information

  
BN-48 (UHU)

AC Power supply
The SP-15 was supplied with a highly compact mains power supply unit (PSU) that was suitable for all common AC mains voltages in the world, between 95 and 235 V. It produces the LT and HT voltages for the transmitter.

It is slotted into the left side of the transmitter or, in the case of the modified Dutch FSS-7/NL, into the left side of the special junction box.
  
Mains AC power supply unit

DC Power Supply
When no mains AC network was available, it was also possible to power the SP-15 from a 12V DC source, such as the battery of a car. This was done by swapping the AC PSU for a DC one.

It contains a power inverter that converts the 12V DC input into 6.3V for the filaments and a HT AC voltage for the transmitter's valves. Like the AC PSU, it is slotted into the left side of the transmitter. It contains a relay to prevent the DC power source from being connected the wrong way around.
  
DC battery inverter

FSK Modulator   wanted
For burst transmissions at very high speed, such as the 1200 baud mode of the MMP burst encoder shown above, the existing keying methods were not adequate and this primitive FSK Modulator was developed as an alternative.

It was inserted between the crystal and the crystal socket of the FS-7 transmitter.


 More information
  
FSK modulator and crystal

Calibrator
The analogue scale of the FE-8 (BN-58) receiver can be calibrated with this external calibrator, that is connected to the receiver's antenna and ground sockets.

It is powered by an internal 6V battery, which is identical to the one used in the FE-8 itself. It was supplied with the SP-15 sets that were used in Germany.

 More information
  
FE-8 calibration device

RT-3 burst encoder connected to the FE-7 transmitter MMP connected to the FS-7 transmitter (SP-15)
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RT-3 burst encoder connected to the FE-7 transmitter
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MMP connected to the FS-7 transmitter (SP-15)

Accessories
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.
  

The rather cheap-ish morse key Morse check light Side-tone cable Roll-up antenna Crystal tuner Crystal storage box Contents of the crystal box
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The rather cheap-ish morse key
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Morse check light
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Side-tone cable
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Roll-up antenna
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Crystal tuner
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Crystal storage box
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Contents of the crystal box

Webbing kit
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.
  
The FS-7 transmitter inside one of the pockets

The complete webbing pack The complete webbing pack The complete webbing pack The complete webbing pack The complete webbing pack The FS-7 transmitter inside one of the pockets The FS-7 transmitter inside one of the pockets
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The complete webbing pack
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The complete webbing pack
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The complete webbing pack
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The complete webbing pack
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The complete webbing pack
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The FS-7 transmitter inside one of the pockets
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The FS-7 transmitter inside one of the pockets

Burst encoders
In order to reduce the chance of detection and interception by means of Radio Direction Finding (RDF), the SP-15 was often used in combination with a so-called burst encoder. It allows a pre-recorded message to be played back — commonly in morse code — at very high speed. As the transmitter is only on the air for a very short moment, there will be less chance to do a proper triangulation and locate the radio station, which would have endangered the entire operation.

Kurzsignalgeber
KSG
NATO-issue RT-3 burst encoder American GRA-71 burst encoder German Speicher (memory) burst encoder German MMP burst encoder
MMP
KSG Burst Encoder
In the early days of the SP-15, the burst encoder of the predecessor, the KSG-Sender, was used to send short messages of 20 to 25 digits in morse code. The KSG consisted of a metal disc in which a number of mechanically coded inserts had to be installed. A crank was then used to rotate it.

 More information
  
KSG with the crank in place

RT-3 Burst Encoder
The second 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
  
The RT-3 burst encoder. Click for additional information.

GRA-71 Burst Encoder
For a long time, the SP-15 was used in combination with the American military GRA-71 burst encoder that allowed the dots and dashes of the morse characters to be recorded on a piece of ferro-magnetic (audio) tape.

Especially for use with the SP-15, they were supplied in grey hammerite, rather than the usual black as used by the US Army.

 More information
  
CO-3A burst encoder as used with the GRA-71, in grey hammerite, especially for the SP15.

Speicher Burst Encoder   wanted
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
  
Speicher (memory) burst encoder

MMP Burst Encoder
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-backed CMOS memory and send them at various speeds between 15 and 1200 baud.

 More information
  
High-speed morse burst encoder MMP-B

Synthesizer   FSS-7
Modified FSS-7 used by Dutch Stay-Behind

In The Netherlands, the SP-15 was used for the national Stay-Behind organisation O&I (Dutch: Operatiën en Inlichtingen) during the 1960s and 1970s. O&I agents were given two green water-tight containers that could be burried underground, e.g. in the garden of their house. One of these contained a hand gun, ammunition, cash money and gold (the latter for bribing people).

The other one contained the SP-15 radio set, together with a wide range of accessories such as antennas, crystals, spare parts and a burst encoder. The image on the right shows a typical modified Dutch FSS-7 (SP-15) with synthesizer.

Around 1975, the set was given a mid-life upgrade by the addition of a synthesizer for the transmitter and a purpose-built junction box.

 More information
  
Complete setup with standard morse key

Speicher Burst Encoder   wanted
The Dutch Stay-Behind version of the SP-15 is known to have been used in combination with various burst encoders. Some of these have been on display at the Dutch Signals Museum [4].

The only known surviving FSS-7 container, which is now in the collection Museum Jan Corver, was found with the Speicher burst encoder shown in the image on the right.

 More information
  
Dutch FFS-7 (SP-15) set with Speicher burst encoder

References
  1. Helmut 'Jim' Meyer, HS0ZHK, My way to Ham - Radio and beyond
    Website QRZ.COM. Personal correspondence. Retrieved April 2013.

  2. Museum Jan Corver, Exhibition Secret Messages
    The Dutch version of the SP-15 was on display during this exhibition.

  3. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN: 0952063-36-0, September 2004.

  4. Museum Verbindingsdienst, Burst Encoders for Stay-Behind use
    Dutch Signals Museum. Photographed by Crypto Museum. 25 February 2009.

  5. Geschiedenis van de Sectie Algemene Zaken, Hoofdstuk VI, Consolidatie
    History of the Section General Affairs, Chapter 6, Consolidation. pp. 79 - 80 (Dutch)
    Describing the period May 1970 - December 1981. Dutch National Archives. Top Secret. Partly declassified and released in 2007 under the FOI Act.

  6. Armin Müller, Wellenkrieg
    ISBN 978-3-86153-947-6, June 2017. pp. 100—103.

  7. Detlev Vreisleben, Personal correspondence
    Retrieved May 2018.
Further information
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Crypto Museum. Created: Monday 03 August 2009. Last changed: Thursday, 22 November 2018 - 21:40 CET.
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