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KSG-Sender   FS-8
Spy radio transmitter - wanted item

The KSG-Sender (KSG transmitter), also known as FS-8 1 , was a 7.5 Watt crystal-operated short wave (SW) clandestine transmitter, developed around 1957 by the German intelligence service, the Bundesnachrichtendienst (BND) and built by Hirschmann. The transmitter was intended for use by the German Stay-Behind Organisation (SBO, often referred to as Gladio), where it was used in combination with a mechanical burst encoder, the so-called Kurzsignalgeber or KSG (short message transmitter). The KSG-Sender 2 is also known by its BND designator EL-84 Sender [4].

The transmitter measures just 17 x 12 x 4 cm and is built around a single valve (tube). Despite its small size, it has a built in Power Supply Unit (PSU) that allows the device to be connected directly to the 110 or 220V AC mains. At the front right is the power plug. The 3-pin DIN plug at the left is for connection to the accompanying Kurzsignalgeber (KSG), an external electromechanical burst encoder [1].

Two banana-type sockets at the right side are for connection to the wire antenna (red) and a suitable counterpoise or GROUND wire (black).
FS-8 (KSG-Sender) from the former collection of Detlev Vreisleben [1]

The small device at the right is an optional Antenna Monitor that was used to assist when tuning the antenna for maximum power output. At the front are three knobs: a black one for selection of the desired frequency range, plus a red and a green knob for the built-in antenna tuner [3].

A suitable crystal for the desired frequency should be inserted into the socket at the front left. Two neon lamps and a small glow lamp are present for assistance during antenna turing. They are visible through small holes in the top of the case. The rightmost neon lamp (above the green knob was omitted from a later version of the transmitter. The initial version of the FS-8 was suitable for frequencies between 3 and 15 MHz (later enhanced to: 3 - 16 MHz).

The FS-8 was succeeded around 1960 by the FS-7, a more powerful transmitter (20W) with an external power supply unit, built by Pfitzner in Germany. The FS-7 became part of the SP-15 spy radio set that was used for more than two decades. During the first years of the SP-15, the Kurzsignalgeber (KSG) was still used as the burst encoder, until it was replaced by the RT-3.

  1. The name FS-8 has not officially been confirmed.
  2. Confusingly, some official BStU 3 documents [5] use the abbreviation KSG for Kurzwellen-Sendegerät (Short Wave Transmitter) rather than for Kurzsignalgeber (burst encoder). 'KSG' was used in conjunction with the FS-8 as well as with the later FS-7 (SP-15) transmitter.
  3. BStU is the Bundesbehörde für die Stasi-Unterlagen, the Federal Commisioner for the Records of the State Security Service (Stasi) of the former German Democratic Republic (DDR).

Burst transmitter
In order to minimise the chance of detection and interception, the FS-8 was supplied with a so-called burst encoder, a small device that allowed a pre-recorded messages to be played back in morse code at very high speed. This minimised the time 'on air', and hence reduced the risk of detection, interception and capture.

The image on the right shows the Kurzsignal­geber (KSG) that was designed to complement the KSG-Sender.

 More information

KSG with the crank in place

The FS-8 is extremely small considering its age, especially when we realise that the mains PSU is built-in. The image on the right [2] shows the interior, seen from the top. The AC transformer is at the rear right, with a neon indicator on top.

The only valve is at the far left. The image gives a clear view of the band selector and the antenna tuning capacitors. At the front right are the two banana sockets for the antenna and the ground (counterpoise). Both sockets are white here. In the foreground the DIN plug for connection to the KSG burst encoder.
Interior of the FS-8 (KSG-Sender) [2]

KSG-Sender Top view Interior of the KSG-Sender Interior of the KSG-Sender Front view Enclosure
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Top view
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Interior of the KSG-Sender
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Interior of the KSG-Sender
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Front view
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Models 1
  1. Frequency ranges: 3-4, 4-6, 6-10 and 10-15 MHz
  2. Frequency ranges: 3-5.6, 5.6-8.2, 8.2-13.2, 13.2-16 MHz
  1. Although no documentation has been found to date to support this, it is believed that there were two versions of the FS-8 (KSG-Sender), and that model 2 was the later one [1].

Wanted item
Crypto Museum are currently looking for a FS-8 to complement the KSG burst encoder in our collection. If you have one available, or if you know where to find one, please contact us. Furthermore, any additional documentation and real-life stories about the use of the F-8 (KSG-Sender) are most welcome.

  1. Bedienungsanleitung für K.S.G. 1
    Operating instructions (German) — Annotated. Date unknown.
  1. Kindly supplied by Detlev Vreisleben [1].

  1. Detlev Vreisleben, Images, documentation and backgrounds of KSG and KSG-Sender
    Personal correspondence. December 2014. December 2016.

  2. Günter Hütter, Interior of the FS-8
    Crypto Museum, July 2009.

  3. Bundesnachrichtendienst (BND), KSG Operating instructions (German)
    Date unknown, probably around 1957. 6 pages diary format. 1

  4. Helmut 'Jim' Meyer, HS0ZHK, My way to Ham - Radio and beyond
    Website QRZ.COM. Personal correspondence.

  5. BStU 000476, Kurzwellen-Sendegerät (KSG) älter Bauart...
    VVS JHS o001 - 70/88. Page 145. 1

  6. BStU 000477, Modernes zweiteiliges halbautomatisches Kurzwellen-Sendegerät (KSG)...
    VVS JHS o001 - 70/88. Page 146. 1
  1. Kindly supplied by Detlev Vreisleben [1].

Further information
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Crypto Museum. Created: Friday 05 December 2014. Last changed: Monday, 26 August 2019 - 08:45 CET.
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