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Digital spy radio receiver - wanted item

KE-30 was a small receiver, built around a digital frequency synthesizer, developed in the early 1980s by Heinrich Pfitzner GmbH in Bergen-Enkheim (Germany) as part of a revised version of the SP-20 spy radio set, known as Projekt 928. Some prototypes were built but the receiver was never taken into large-scale production. Instead the existing FE-8 (BN-58) remained in use.

The enclosure of the KE-30 receiver is identical to that of the KS-30 frequency synthesizer. It has the same controls and the same 5-digit LED display. The only difference is that the space at the right hand side of the front panel, is taken by a LED-bar signal strength indicator, whereas the KS-30 has a 20-pin socket in this position.

The image on the right shows one of the very few KE-30 prototypes that have survived. 1
KE-30 receiver is grey enclosure with dark front panel [x] WANTED ITEM

Development of a revised version of the SP-20 spy radio set, known as Projekt 928, was started in the late 1970, and the new system was planned for release in or around 1983. It consisted of the existing S-6800 transmitter, the ASG-6800 antenna tuner (both made by AEG Telefunken) and KS-30 frequency synthesizer (to replace the crystals) made by Heinrich Pfitzner GmbH.

New in Project 928 was the digital KE-30 receiver, that was aimed to replace the existing FE-8 receiver. The FE-8 was developed by Wandel & Goltermann in the late 1950s, and had already been used with the SP-15 spy radio sets. When the SP-20 replaced the SP-15 in the mid-1970s, no good alternative for the FE-8 was found and so it was issued again with the SP-20.

Pfitzner was comissioned to develop the new KE-30 receiver, which was ready in 1983. Despite the fact that several prototypes had been built, the receiver was never taken into large-scale production, as orders for development of the pan-European FS-5000 had already been given.

  1. Please note that this receive is not part of our collection. We have no information about the current whereabouts of it. Crypto Museum are currently looking for a KE-30 receiver for its collection.

Block diagram
The simplified block diagram below, is based on the original Pfitzner documentation, and shows roughly how the KE-30 works [1]. The device is built around a PLL synthesizer that is very symilar to the external KS-30 synthesizer — also made by Pfitzner — that was used in combination with the S-6800 transmitter. Both that synthesizer and this one, have a TXCO frequency of 74.97 MHz.

The received signal, in the 2-24 MHz range, is first led through a band-pass filter followed by a 32 MHz low-pass filter, and then mixed with the variable (77-99 MHz) frequency from a digital PLL synthesizer. The resulting 75 MHz IF signal is then mixed with the TCXO frequency of 74.97 MHz, resulting in a second IF frequency of 30 kHz. This 30 kHz signal is further processed in a TCA440 AM receiver IC with built-in AGC (Automatic Gain Control) and a free-running oscillator at 30 kHz. The output of the TCA440 is then demodulated and amplified to headphones level.

The second IF frequency of 30 kHz was very common for professional receivers of Telefunken and Pfitzer at the time. In fact, the circuit and the chosen frequencies are very similar to those of the contemporary Teletron TE-704 short-wave receiver, which was also manufactured by Pfitzner.

At present, not much is known about the circuit diagram and the internals of the KE-30 receiver, but fortunately we received the photograph below from Louis Meulstee [3], which shows the upper section of the device's interior. By examining the various components and their position, in combination with the block diagram above, we are able to make a few educated guesses.

Upper section of the KE-30 receiver. Photograph kindly supplied by Jim Meyer [1].

At the bottom left is the RF input connector and the RF input filter, which consists of a switchable band-pass filter and a 32 MHz low-pass filter. At the bottom right is the VCO (Voltage Controlled Oscillator) that is a crucial part of the frequency synthesizer, which is located at the bottom side.

The upper half of the picture shows the 2nd IF stage, with the TCA440 Automatic Gain Control (AGC) and probably the audio amplifier. At the top right is a five-stage 30 kHz IF filter that sits between the output of the 2nd mixer and the input of the TCA440. The board at the bottom side (not shown here) contains the PLL circuit – with the TCXO and the dividers – and the control logic.

Help wanted
At present, no further information about the KE-30 receiver is available to us. If you can provide additional details, please contact us.

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

  2. Siemens, TCA440 AM Receiver Circuit (datasheet)
    Date unknown.

  3. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004. Personal correspondence January 2018.
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Crypto Museum. Created: Sunday 04 September 2016. Last changed: Monday, 14 September 2020 - 08:56 CET.
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