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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 as the 'French 1950s Miniature' [1], but recent research has revealed that it most likely is not French but probably East-European.

The modular radio set consists of three small identically sized metal boxes, each of which has a top lid and measures approx. 165 x 85 x 60 mm. A complete set consists of three units: (1) mains power supply unit (PSU), (2) transmitter (TX) and (3) 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. In addition, we found a more or less complete set in Bulgaria in 2022.
  
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 (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 Mark 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) a French intelligence agency, mainly because of certain acccessories that were found with it, but this now seems unlikely.


Transmitter Mark 1
As we have identified two versions of the transmitter, we will call the one that we think is the oldest one: Mark 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 in Budapest (Hungary). It is housed in a black wrinkle paint enclosure. Photographs of the interior can be found below.

Older model transmitter (Mark 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
A
×
A
1 / 8
Transmitter Type 1
A
2 / 8
Transmitter Type 1
A
3 / 8
Front panel
A
4 / 8
Close-up of the meter, revealing the serial number 303104
A
5 / 8
Interior
A
6 / 8
Interior
A
7 / 8
Bottom view
A
8 / 8
Close-up of the valve

Transmitter Mark 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 Mark 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 connector is very uncommon for spy radio sets, but allow quick and faultless connection.

Newer model transmitter (Mark 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 Mark 1 transmitter, the serial number is written on the scale of the meter. Note that the meter as well as the tuning indicator lamp are made in East-Germany (DDR) by VEB RFT.

Most of the parts inside the device cannot be attributed to a particular manufacter, but it is certain that the dark red resistors are made by Czech manufacturer Tesla, whilst the bright green resistors are made by Ленинградский завод No. 130 (Leningrad Factory No. 130) in Russia.

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)
B
×
B
1 / 8
Transmitter type 2 with top lid removed
B
2 / 8
Transmitter type 2 with top lid removed
B
3 / 8
Front panel
B
4 / 8
Close-up of the meter
B
5 / 8
Interior
B
6 / 8
Interior
B
7 / 8
Tuning lamp (made by RFT in East-Germany)
B
8 / 8
Resistors (made by Tesla in Czechoslovakia)

Receiver Mark 1
The receiver in our collection is housed in a black enclosure and has a serial number starting with '303', which is why we think it is the earlier model (which we have called Mark 1). It gets its power from the transmitter and although the receiver shown here has a 3-pin hearing aid-type plug, the bakelite shell of the old 3-pin plug is still present. It was modified for the Mark 2 transmitter.

Older model receiver (Mark 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 details of the interior.

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
C
×
C
1 / 8
Type 1 receiver with type 2 connector
C
2 / 8
Receiver connected to a type 2 transmitter
C
3 / 8
Front panel
C
4 / 8
Interior
C
5 / 8
Interior
C
6 / 8
Regeneration control
C
7 / 8
Bottom view
C
8 / 8
Tuning capacitor and scale

PSU   wanted
Unfortunately, we do not have an original PSU in our collection, so the only image 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 (Mark 2) as it appears to be housed in a green enclosure. Furthermore it has connections for the older transmitter (Mark 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 (Mark 2).

Newer model PSU (Mark 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 have been recorded:

S/N Module Version Case Remark
303033 TX 1 Black Photographed by Staritz [2] (complete set)
? RX 1 Black Photographed by Staritz [2] (complete set)
? PSU 1/2 Green Photographed by Staritz [2] (complete set)
? PSU 1/2 Black Crypto Museum 1
303075 RX 1 Black Crypto Museum
303077 RX 1 Black Crypto Museum 1
303104 TX 1 Black Crypto Museum
4020 TX 2 Green Crypto Museum
4111 RX 2 Missing Crypto Museum 1
4112 TX 2 Black Crypto Museum 1
It is possible that the serial numbers of the Mark 1 sets all start with '303' and that '4' was used to identify Mark 2 sets. Note that the Mark 1 units have a 6-digit serial number, whilst the Mark 2 units have a 4-digit number. In both cases however, the actual serial number consists of the last three digits.

  1. Found in Bulgaria.

All-in-one set   wanted
In 1992, the radio set shown in the image below was photographed, most likely by Rudolf Staritz in Germany [3]. The design of this radio set is very similar to that of the individual units shown above. The same knobs are used and the typeface of the engraved text is identical, which suggest that it was made by the same agency. Some of the knobs may have been swapped later in life.

The radio is housed in an aluminium case with leather grip, visible at the bottom, and consists of three modules: PSU, receiver and transmitter. At the right is a compartment for the cables.

It seems to be more advanced, and probably more powerful, than the miniature units shown above. Receiver and transmitter each have three frequency bands (rather than one or two).

The serial number is written on the scale of the meter of the PSU and is probably 0619.
  
All-in-one radio set. Click for a close-up [3].

We have no information about the current whereabouts of this radio set, but if you know someone with a similar set, please contact us, as it might give us the possibility to investigate it further.


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
  • Hungary
  • Russia (USSR)
  • United Kingdom (UK)
  • United States (USA)
References
  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.

  3. Unknown author (probably Rudolf Staritz), All-in-one radio set
    Obtained via Heinz Lissok. Retrieved June 2012.
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Crypto Museum. Created: Sunday 27 September 2015. Last changed: Saturday, 14 May 2022 - 06:13 CET.
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