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Unidentified spy radio set
Minature valve-based spy radio set

It doesn't happen very often, but here we have a Cold War spy radio set of which the origin is a mystery to us. For this reason we are asking your help in identifying it. The set is described in Louis Meulstee's book Wireless for the Warrier, Volume 4 [1] as the 'French 1950s Miniature', but recent research has revealed that it most likely is not French but probably East-European.
The modular spy radio set consists of three small identically sized metal boxes, each of which has a top lid and measures approx. 16.5 x 8.5 x 6 cm. A complete set consists of a mains power supply unit (PSU), a transmitter (TX) and a receiver (RX). At least two different versions of the set have so far been identified.

The image on the right shows two different versions of the transmitter and a (modified) receiver, as they were found by Crypto Museum in Austria in 2013. They are described in more detail below, along with a complete set.
Three units from the Crypto Museum collection: a receiver and two versions of the transmitter.

As you can see in the image above, the set came in two colours: black wrinkle paint and green wrinkle paint. The receiver covers a contiguous frequency range of 3.5 to 8 MHz. On the crystal-operated transmitter, this is divided over two ranges, marked I and II (or 3 and 6 on the later version). The only known photograph of a complete set is this one, made by Rudolf Staritz [2]:

Photograph of complete set. Kindly supplied by Rudolf Staritz [2]. Click to enlarge.

The same photograph is also shown in the book Wireless for the Warrier, Volume 4 of 2004 [1]. From top to bottom it shows the PSU, the transmitter and the receiver. The transmitter is connected to the PSU by means of 5 wires. The receiver gets its power from the transmitter via a 3-wire cable. Looking closely at the above photograph, it appears that the lower two units have a black case, whils the case of the PSU is green. Also note the two hearing aid connectors (a black and a white one) on the front panel of the PSU. They were probably for the Type 2 transmitter.

Unfortunately, the origin and the current whereabouts of the above set is unknown. For several reasons it was thought at the time that it was made by (or for) the French intelligence agency, mainly because of certain acccessories that were found with it.
Transmitter Type 1
As we have identified two different types of transmitter, we will call the one that we think is the oldest one: Type 1. It has banana-type connectors for the PSU, the morse key and the receiver, and is built around a single DLL101 valve (tube) made by Tungsram. It is housed in a black wrinkle paint case. Detailed photographs of this version of the transmitter and its interior below.

Older model transmitter (type 1)

This transmitter has two frequency ranges, marked I and II, that are selectable with a slide switch at the bottom right. At the bottom left is a 5-wire cable with banana-type plugs at the end, for connection to the PSU. The wires are labelled with the voltages: -1.4, +1.4, -180, +180 and +90.
Transmitter Type 1 Transmitter Type 1 Front panel Close-up of the meter, revealing the serial number 303104 Interior Interior Bottom view Close-up of the valve

Transmitter Type 2
The other type of transmitter was probably made at a later date, as it is built around two DLL101 valves. For this reason we have dubbed it Type 2. It is housed in a green wrinkle paint case and uses old 3-pin hearing aid-type sockets for connection to PSU, morse key and receiver. This type of connectors is very uncommon for spy radio sets, but allow quick and faultless connection.

Newer model transmitter (type 2)

Note that the two sockets at the top left have different colours, This was probably done to avoid mistakes when connecting the PSU, which has two identically coloured plugs (see below). Like with the Type 1 transmitter, the serial number is written on the scale of the meter, but note that the meter is made by VEB RFT, an East-German manufacturer. Also note that the tuning indicator lamp is made by RFT and that some resistors are made by Czechoslovakian manufacturer Tesla.
Transmitter type 2 with top lid removed Transmitter type 2 with top lid removed Front panel Close-up of the meter Interior Interior Tuning lamp (made by RFT in East-Germany) Resistors (made by Tesla in Czechoslovakia)

Receiver Type 1
The receiver in our collection is housed in a black enclosure and has a serial number starting with '30', which is why we think it is the earlier model (which we have called Type 1). It gets its power from the transmitter and although the receiver shown here has a 3-pin hearing aid-type plug, the bakelite casting of the old 3-pin plug is still present. It was modified for the Type 2 transmitter.

Older model receiver (type 1)

The receiver is built around three miniature battery valves: 2 x 1T4T and 1 x 3S4T. It consists of an RF stage, a regenerative detector and an AF output stage. For CW reception, the detector can be brought into oscillation [1]. Check out the images below for further details.
Type 1 receiver with type 2 connector Receiver connected to a type 2 transmitter Front panel Interior Interior Regeneration control Bottom view Tuning capacitor and scale

Unfortunately, we do not have an original PSU in our collection, so the only image of it that we can show is the one from the complete set shown at the top of this page. We assume that this is the later version (type 2) as it appears to be housed in a green enclosure. Furthermore it has connections for the older transmitter (type 1) as well as two 3-pin hearing aid plugs (a white one and a black one) that are probably intended for connection of the newer transmitter (type 2).

Newer model PSU (type 2)

The PSU is suitable for virtually any AC mains voltage in the world, selectable between 100 and 230V in 10V steps, by means of the rotary selector at the centre.
Serial numbers
Each of the units has a serial number that is impressed on the inside of the front panel. On the transmitter, it is also written at the center of the white scale of the meter. On the receiver it is written at the low end of the frequency scale. The following serial numbers are currently known:
  • 303033
    TX type 1
    Photographed by Staritz [2] (complete set)
  • ?
    TX type 1
    Photographed by Staritz [2]
  • ?
    PSU type 2
    Photographed by Staritz [2]
  • 303075
    RX type 1
    Crypto Museum collection
  • 303104
    TX type 1
    Crypto Museum collection
  • 4020
    TX type 2
    Crypto Museum collection
It is possible that the serial numbers of the type 1 sets all start with '30' and that '40' was used to identify type 2 sets. It is also possible that the type 1 sets were all black and that the type 2 sets were all green, although this is uncertain due to the limited number of units that have survived.
Please help
Please help us identifying this clandestine radio set, by providing as much information as possible. If you know in which country the set was built, by who it was used, if you have any documentation or if you know a collector who has a similar set, please contact us.

So far we have identified components from the following countries:
  • DDR (East-Germany)
  • Czechoslovakia
  • Denmark
  • USSR
  1. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004

  2. Rudolf Staritz, Photograph of complete French 1950s Miniature set
    Obtained via [1], September 2015.

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