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BS-5000
Modular base station for FS-5000 - Wanted item

BS-5000 was the name of the base stations of the SY-5000 secure communication systems. It was capable of receiving and processing encrypted messages to and from FS-5000 field stations. It was used by stay-behind organisations, Special Forces (SF) and intelligence agencies. As the base station consists of a number of products, it comes in many variations under various names.

The FS-5000 field station was capable of sending digital data at very high speed (2000 baud) over a narrow-band HF radio channel, using a sophisticated technique called Vestigial Side Band modulation (VSB). This was done to minimise the risk of Radio Direction Finding (RDF or DF). It takes the FS-5000 transmitter just 0.8 sec. to send a typical 55-character message.

Communication path between BS-5000 base station and FS-5000 field station

Creating a VSB-signal is relatively straight-forward, but it requires a very complex and sophisticated decoder at the receiving end. For this reason the receiver uses 'ordinary' single-channel SSB-modulated Frequency Shift Keying (FSK) at a speed of just 75 baud. As a result, direct communication between two FS-5000 field stations is not possible. An FS-5000 field station can only communicate with a BS-5000 (or the later BS-7010) field station.

Block diagram of the BS-5000 Base Station

The image above shows the block diagram of a typical BS-5000 base station. At the heart of the base station is a PR-5000 Central Processing Unit (CPU) and a KG-5000 Crypto Unit, that allows incoming and outgoing data to be decrypted and encrypted in real-time. The teleprinter is used to control the CPU, whilst a separate terminal (Televideo 955) is used for entering messages, cryptographic keys and RX/TX frequencies. Note that the RX and TX antennas have to be 150 metres or more apart in order to avoid interference.
 
Practical configuration
Please note that the above block diagram shows internal model numbers that were issued especially for the FS-5000 project. The block diagram is based on the information given in the user manual and is used for a technical and functional explanation only. It does not represent the actual configuration of the base station, which was largely built from existing parts.

Actual implementation of the BS-5000 Base Station

In reality, the base station consisted of separate transmitters, receivers, modems and other equipment from various manufacturers. The block digram above shows an example of a practical implementation of the BS-5000 base station, built from standard off-the-shelf products.
 
For reception, the highly acclaimed Telefunken E-1800/A receiver was used. This receiver was also sold under the AEG, TST and DASA brands. At the time it was the only receiver with a Digital Signal Processor (DSP) that was capable of demodulating VSB signals. A Telefunken Echotel modem was used for modulation and demodulation of the digital signals, as well as for encryption and decryption of the data. All components were controlled by a single PC that could also be used as a data-entry terminal.

For transmission, a standard Rohde & Schwarz XK852 transceiver is used. This is a heavy duty transmitter with a configurable output power of up to 100 W. The image on the right shows the interior of a mobile base station as it was shown in the 2006 Telefunken brochure [4]. The various parts are mounted in the 19" rack at the center.
  

At the top is the transmitter and, immediately below it, a Telefunken E-1800 receiver. The middle part of the rack contains the ECHOTEL and ARCOTEL modems. In the bottom section are further transceivers and power supply units. The controlling PC is at the far left. This semi-permanent (mobile) station was also used with the HF-7000 radio set. The image above was taken from the old HF-7000 brochure [4]. Funnily, the image in the brochure was erroneously mirrored.
 
EKASUS
As the behaviour of the HF radio bands changes continuously (propagation), the suitability of a certain frequency for long distance communication depends on a number of circumstances, such as time of the day (or night), time of the year, temperature, distance, etc. This requires a complex table of usable radio channels that changes continuously. For this reason, the BS-5000 station was often equipped with multiple E-1800/A receivers, all controlled from a central PC.

Later implementation of the BS-5000 Base Station

The E-1800/A receivers were later replaced by the fully digital PC-based E-2000LH-5 receivers that were also manufactured by Telefunken. At some point, Telefunken even introduced the EKASUS, a PC-based frequency management system with built-in propagation prediction. A similar system was later used with the HF-7000 radio set and became known as EKS-7000 [4].
 
Wanted
At present we have no photographic image of a complete BS-5000 or BS-7010 base station. It is possible that some countries used different base stations than the one described here. It is also possible that it was known by a different name or number. If you have any additional material, documentation, information, or - better - a complete base station, please contact us. For our demonstration setup, we are also looking for an E-1800/A receiver.
 
References
  1. Feldstation FS-5000M, Technisches Handbuch, Teil 1, Beschreibung
    Field Station FS-5000, Technical Manual, Part 1, Description (German).
    March 1994.

  2. Feldstation FS-5000M, Technisches Handbuch, Teil 2, Bedienungsanleiting
    Field Station FS-5000, Technical Manual, Part 2, User Manual (German).
    March 1994.

  3. Telefunken Racoms, HF Gerätefamilie 7000
    12-page full-colour brochure (German). April 2009. Retrieved August 2010.

  4. Telefunken Racoms, HF Gerätefamilie 7000
    12-page full-colour brochure (German). April 2006. Retrieved May 2013.

Further information

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