Homepage
Crypto
Spy radio
Index
Glossary
USA
USSR
UK
Germany
Poland
Czechoslovakia
Hungary
Yugoslavia
OWVL
Stay-Behind
Special forces
Receivers
Other
Burst encoders
Intercept
Covert
Radio
PC
Telex
Telephones
People
Agencies
Manufacturers
• • • Donate • • •
Kits
Shop
News
Events
Wanted
Contact
About
Links
   Click for homepage
12-WG
Modular spy radio set - under construction

12-WG was a valve-based modular clandestine radio station, or spy radio set, developed in 1953 by Wandel & Goltermann in Germany for Organisation Gehlen (OG), the forerunner of the current German intelligence service, the Bundesnachrichtendienst (BND) [1]. The radios were typically used for agent communication (espionage) and for clandestine operations behind enemy lines.

The radio set was available in a 2-piece and in a 4-piece version, with the latter being the more common one as it was easier to hide. It could be powered directly from the AC mains virtually anywhere in the world with a voltage between 90 and 230V AC. Alternatively, it could be powered by a 6V motorcycle or car battery, which was most useful when operating behind enemy lines.   
Complete 4-piece 12WG set

The 12-WG had a long operational life and it took 10 years before all sets had been replaced by modern alternatives. The last units were decomissioned in 1963 [2]. The 12WG was succeeded around 1956 by the FS-8 (KSG) transmitter, that was also built by Wandel & Goltermann, and two years later, in 1958, by the more versatile SP-15 of which W&G only built the two receivers.

Complete 4-piece 12WG set Complete set with the metering unit (12WG/M) missing Receiver 12WG/E Transmitter 12WG/S Power Supply Unit (PSU)
Variants
  • 4-piece version
    This version consisted of the four units listed below, interconnected via Jones plugs and sockets that are integrated in the sides of the units. Due to the smaller size of the individual modules, this version is easier to conceal. Most of the surviving 12WG sets are of this type.

  • 2-piece version
    The version is electrically identical, but consists of only two modules: a combined receiver/transmitter and a combined PSU with metering unit. The two modules are interconnected via Jones connectors. This variant was less common than the 4-piece one.
4-piece version
The diagram below shows the various features of the receiver. The 3 - 16.4 MHz frequency range is divided over 3 bands that can be selected with the rotary switch at the bottom right. The large frequency scale allows accurate tuning and has an additional fine-tuning knob at the bottom edge. The dial has three scales, one for each frequency band, plus a 4th linear scale. The unit should be plugged into the PSU. Antenna and a headphones are connected at the top left.


The transmitter is about half the size of the receiver and is shown in the diagram below. It should be connected to the Metering Unit, which in turn is connected to the PSU. A suitable crystal for the desired frequency should be placed on the socket at the right and a wire antenna must be connected to the banana-type socket. Counterpoise must be connected to the Metering Unit, just like the morse key. After tuning the oscillator and the antenna, the transmitter is ready for use.


The diagram below shows the 12WG/N power supply unit (PSU). It is the central piece of the radio set and connects to the AC or DC power source, the receiver and the metering unit (which in turn is connected to the transmitter). The PSU can only be used together with the metering unit, as the latter contains parts of the PSU circuitry that could not be fitted inside the PSU's enclosure.



History
...

Parts
12WG/E - Receiver (Empfänger)
RX
12WG/S - Transmitter (Sender)
TX
12WG/N - Power Supply Unit
PSU
12WG/M - Metering unit 'Mouse' morse key AC mains power cable
AC
6V DC power cable
DC
Battery charging cable
Receiver   12WG/E
The receiver is probably the most sophisticated part of the 12WG set. It measures 15 x 13.5 x 5.5 cm and has the same form factor as the PSU. It can be tuned to any frequency in the 3 to 16.4 MHz range, divided over 3 colour-coded bands.

The big knob at the center is the frequency adjustement, which can be fine tuned with the aluminium wheel at the south edge. The knob at the left is for adjusting the volume. A small lever, just above the volume control, is for adjusting the amount of feedback. It should be tuned for maximum noise level.
  
Receiver 12WG/E

Transmitter   12WG/S
The transmitter is housed in one of the smaller enclosures. It measures 8 x 13.5 x 5.5 cm and is built around a single valve. It is crystal-operated and is suitable for frequencies between 3 and 15 MHz, divided over 4 bands. Apart from the band selector, it has knobs for adjusting the crystal oscillator and for tuning the antenna, both of which should be used in combination with the separate 12WG/M Metering Unit.

A suitable wire antenna should be connected to the banana socket on top of the unit.
  
Transmitter 12WG/S

Power Supply Unit   12WG/N
The PSU is a vital part of the 12WG, at it provides the HT and LT voltages for the receiver and the transmitter. It measures 15 x 13.5 x 5.5 cm and is the heavyest module of the set. It contains the transformer, for AC use, and a vibrator pack, which is used when powering the set from a 6V DC source such as the battery of a motorcycle.

The PSU has three sockets: one for the metering unit (west side), one for the receiver (south side) and one for the power cable. The latter is located at the east side of the unit and is marked with a red dot. Cable wiring is specified below.
  
Power Supply Unit (PSU)

Metering Unit   12WG/M
The small module that sits at the top left of the complete radio set, is the so-called metering unit. As the name suggests, it contains a meter and a rotary switch to select what you want to check: the Anode voltage (HT), the 6.3V filament voltage (LT) or the antenna current.

The metering unit is connected to the PSU and the transmitter, and handles the power, antenna and morse key lines to the transmitter. Unfortunately, the metering unit is missing from the set in our collection.
  
12WG/M Metering Unit. Photograph kindly supplied by Detlev Vreisleben [2].

Morse key
Surviving 12WG radio sets have been found with a variety of morse keys. Although the 12WG did not come with a purpose built morse key, it was commonly supplied with a wartime 'leftover', such as the Ta.P. Wehrmacht key shown here.

This key came with a 1 metre long rubber cable with a 2-pin plug at the end. This standard Wehrmacht plug has a pin distance of 19 mm and directly fits the morse key socket of the 12WG/M unit.
  
Ta.P. Wehrmacht morse key

Alternative morse key
Another example of a morse key that was frequently issued with the 12WG, is the TKP or Maus (mouse). It came in two variants: with a circular knob and with a half-moon knob. They were typically issued with spy radio sets during the war, but were more difficult to operate than the Ta.P. Wehrmacht keys.   
German WWII 'mouse' type morse key

AC power cable
The 12WG can be powered directly from the AC mains, in virtually any place or country in the world with a mains voltage between 90 and 230V, selectable with a rotary selector on the PSU. The cable shown in the image on the right was supplied with every 12WG unit as standard.

The cable is fitted with a Hirschmann 2-pin mains plug that fits most of the mains wall sockets in continental Europe. For other countries, the power plug had to be replaced by a local one. The wiring of the AC mains cable is available below.
  
AC mains cable

6V DC power cable
Alternatively, the 12WG could be powered by a 6V DC source, such as the battery of a car or a motorcycle. Especially for use in rural areas, in which no mains AC network was available, the 12WG was often supplied with a 6V motorcycle battery, in which case the PSU was used as a power-inverter.

The cable shown on the right can be used to power the 12WG from a 6V DC source. The wiring of this cable can be found below.
  
6V DC power cable

Battery charging cable
When the 12WG was issued with a 6V DC motorcycle battery, the battery had to be recharged regualarly, which was generally done from an AC mains wall socket using the cable shown in the image on the right.

The cable connects to the AC wall socket as well as to the battery, which is then charged. Note the 0.7Ω current-limiting resistor in the (+) line. The wiring of the charge cable is given below.
  
Battery charging cable

German WWII 'mouse' type morse key AC mains cable Battery charging cable
Interior
Each of the four (or two) units of the 12WG consists of a front panel - to which all components are mounted - and an enclosure in the form of a black metal case shell that is affixed to the sides of the front panel. The case shell has ventilation holes and can easily be separated after removing the screws around the edges of the front panel. Note that the case shell may bind somewhat.

Warning: in the section below, the interior of each of the four units and their circuit diagrams are discussed in more detail. Note that these circuit diagrams have been recreated by ourselves, as the original ones contain too many mistakes. The same is true for the pinout of the 8-pin Jones sockets that are used for connection between the units. Do not trust the original circuit diagram.

Power Supply Unit
The interior of the PSU can be accessed by removing 4 screws, one at each side of the case, and then removing the case shell. This may take some effort, especially if the PSU has never been opened before. Please note that the PSU can not be used standalone, as it is not complete.

All components are mounted to the front panel, which is made of 2 mm thick aluminium. The PSU has three 8-pin female Jones-type sockets at its sides, one for the power source, one for the receiver and one for the metering unit.

Inside the PSU is a large transformer, a vibrator unit, the mains voltage selector, a large selenium diode (the red square at the front) and several smaller components. The image on the right shows the interior of the PSU, which is upside down, shown from the corner of the voltage selector. At the front left is the receiver socket.
  
PSU interior, seen from the south-west corner

The aluminium cylindrical can at the top right, is the vibrator unit, which is used to convert the 6V DC voltage from an external battery into AC, which can then be used to drive the transformer. The vibrator runs at 115 Hz and is mounted in a socket, so that it can easily be replaced in case of a defect. Note that the 6X4 rectifying valve, which is part of the PSU circuit, is not mounted inside the PSU itself but in the metering unit, probably due to lack of space.


PSU interior, seen from the south-west corner Voltage selector Vibrator Vibrator removed Power socket Coil detail Connector to metering unit Bottom view of the PSU with vibrator removed
Metering unit   12WG/M
The metering unit is a rather strange unit, which connects the transmitter to the PSU. It is used for checking the voltages and the antenna current, but also contains the PSU's rectifier valve, which could not be fitted inside the PSU itself. The unit also holds the socket for the morse key.

The interior of the metering unit can be accessed by removing just three screws from the sides of the unit, after which the case shell can be removed. Please note that the metering unit is missing from the 12WG set in our collection, so we have to rely on images that were kindly provided by Nico van Dongen, who has the unit but without the original enclosure [4].

The image on the right shows the interior of the metering unit as seen from the bottom, with the 6X4 rectifier valve at the top (here at the left). The valve is mounted on an aluminium bracket, and is located below the fuse holder and the pre-heat switch.
  
12WG/M interior - bottom view

Note that some capacitors have been replaced and that the reproduction enclosure is made of PCB material. All other parts are original. As the metering unit was completely missing from our 12-WG unit, which appears to be rather common, we had to extract it from the full circuit diagram, in order to build a replica of it. The diagram with the correct pinout of the two Jones connectors is shown below. The layout of both Jones connectors is given further down this page.


Metering unit in reproduction case. Photograph kindly supplied by Nico van Dongen [4]. Metering unit in reproduction case. Photograph kindly supplied by Nico van Dongen [4]. 12WG/M interior. Photograph kindly supplied by Nico van Dongen [4]. 12WG/M interior. Photograph kindly supplied by Nico van Dongen [4]. 12WG/M interior. Photograph kindly supplied by Nico van Dongen [4]. 12WG/M interior. Photograph kindly supplied by Nico van Dongen [4].
Receiver   12WG/E
The interior of the receiver can be accessed by removing five screws from the sides of the case and removing the case shell. This may take some effort, especially if the unit has never been opened before. The best approach would be to lift the front panel at the Jones connector end.

The image on the right shows the interior of the receiver after the case shell has been removed. All components are mounted to the front panel, including an aluminium sub-frame that hold the four valves and several other components.

The receiver is a superheterodyne, consisting of a mixer, oscillator, IF stage with regeneration, detector and AF amplifier. It is suitable for the reception of AM and CW signals. The receiver is connected to the power supply unit via an 8-pin Jones connector, of which only 4 wires are used. Power (HT and LT) is supplied via this connector.
  
Receiver interior

The connector also provides the receiver with a sidetone signal from the transmitter, so that the operator can hear his own morse when transmitting, regardless of the receive frequency. Head­phones and antenna should be connected at the receiver's front panel. Ground is connected to the metering unit. The full circuit diagram of the receiver is given below. Note that it differs from the original diagram that was supplied with each unit, as the latter contains quite a few mistakes.


Receiver interior Receiver interior Valves Connector to the PSU Band selector Volume adjustment capacitor Tuning capacitor Receiver interior - bottom view
Transmitter   12WG/S
The interior of the transmitter can be accessed by removing just three screws from the sides of the unit, and then removing the case shell. This may take some effort, especially if the case has never been opened before. The transmitter is only connected to the Metering Unit, from which it receives the power and which holds the socket for the morse key and the antenna current meter.

The transmitter circuit inside the 12WG/S is very simple and consists of a single 6AQ5 valve, a large coil with several taps, a tuning capacitor, a crystal (socket) and a few passive components.

The image on the right shows a bottom view of the transmitter, seen from the south-east corner. At the front is the 6AQ5 transmitter valve,with the large coild just behind it. The crystal socket is visible close to the edge, just left of the valve socket.
  
Transmitter interior




Transmitter interior Transmitter interior Transmitter valve Connector to the metering unit Antenna matcher band selector Band selector Transmitter tuning capacitor Transmitter interior - bottom view
Restoration
Most of the surviving 12WG radio sets, were released through official government surplus sales in Germany during the 1970s and 80s. Unfortunatly, the metering unit is often missing from these sets, probably as it was thought to be the transmitter. As the laws of the 1970s did not allow a person to possess a transmitter without a proper licence, they were ordered to be destroyed.

The same is true for the 12WG in our collection, that came as a three-part set. Luckily complete sets were available in some museums, such as the Technisches Museum in München (Germany). Furthermore, Dutch collector Nico van Dongen [4] has a complete set, albeit without the original enclosures. From photographs supplied by him and others, we were able to reconstruct the metering unit. In a joint effort with Austrian collector Günter Hütter [5], who also owns an incomplete 12WG set, we were able to recreate an operational authentic metering unit.

Valves   Tubes
 
PSU
Circuit Valve Remark
Rectifier 6X4 Double rectifier
 
Transmitter
Circuit Valve Remark
Oscillator/PA 6AQ5  
 
Receiver
Circuit ZO-47 Remark
Mixer / LO 6J6 Double triode
IP amplifier 9001  
AF amplifier 9001  
Stabiliser 0B2  
Connections
The various modules are interconnected by means of 8-pin Jones connectors, which were very common in the era in which the 12WG radio set was developed, and which can still be obtained relatively easy today. Note that the power cable has a female Jones plug at one end, which can be VERY DANGEROUS when touching the pins whilst the other end is plugged into the mains wall socket. Furthermore, this cable should ONLY be plugged into the PSU socket that is marked with a red dot. Always insert the Jones plug into this socket, before connecting the cable to the mains.

Power Supply Unit   12WG/N
The diagram below shows the pinout of the power input socket at the right side of the Power Supply Unit (PSU), when looking into the socket. Note that the red dot on top of the PSU, marks the top side of the socket. When powering a 12WG, check out the cable wiring diagrams below.

  1. 0V DC in
  2. 6V DC in (from battery or vibrator)
  3. 6.3V out (from vibrator)
  4. Mains AC in
  5. 6V in (from battery)
  6. Mains AC in
  7. 6V out (to battery)
  8. 0V out (to battery)
Transmitter
The diagram below shows the pinout of the female socket on the 12WG/M metering unit into which the transmitter should be plugged, when looking into the socket. This is the same layout as on the soldering side of the female connector at the north side of the transmitter itself.

  1. 0 V (ground)
  2. 6.3 V
  3. 400 V
  4. 400 V
  5. Morse key
  6. -
  7. Antenna current
  8. Antenna current
Receiver *
The diagram below shows the pinout of the female receiver socket on the PSU, when looking into the socket. This layout is identical to the solder side of the female connector at the north side of the receiver itself. Note that the original circuit diagram shown the wrong pinout of this socket.

  1. 0 V (ground)
  2. 6.3 V
  3. 215 V
  4. Sidetone
  5. -
  6. -
  7. -
*) Important: the pinout of the receiver connector shown here is different from the one shown in the original circuit diagram. The circuit diagram is wrong. The one shown here is correct.

Metering unit
The diagram below shows the pinout of the female socket on the PSU to which the metering unit is connected, when looking into the socket of the PSU. This layout is identical to the solder side of the male connector at the east side of the metering unit.

  1. 0 V (ground)
  2. 6.3 V
  3. 215 V
  4. Sidetone
  5. Trafo D
  6. Trafo B
  7. Trafo C
  8. Trafo A
Cable wiring
Mains AC power cable
When connecting the PSU to the AC mains, use the wiring diagram below. The PSU is suitable for AC mains voltages between 90 and 230V, but ensure that voltage selector in the bottom left corner of the PSU is set to the correct voltage before the PSU to the mains. Also ensure that the metering unit is connected before powering the PSU, as it contains the rectifier valve. Do not forget the loop wire between pins 2 and 3. It is necessary to supply the 6.3V to the filaments.

Mains AC cable wiring, when looking into the power socket on the PSU.

6V DC battery cable
The 12WG can also be powered from a single 6V DC source, such as the battery of a car or motorcycle, in which case the transformer is used, in combination with an electromechanical vibrator, as a step-up converter. When powering the 12WG from 6V DC, the cable should be wired as shown below. Do not forget the loop wire for the filaments between pins 2 and 5.

6V DC cable wiring, when looking into the power socket on the PSU.

Battery charging cable
The 12WG was sometimes supplied with a small motorcycle battery that allowed the set to be operated in remote areas where no mains power was available. In such cases it was necessary to recharge the battery from time to time, which could be done with the existing PSU. Especially for this purpose the cable below was supplied. Note the 0.7 Ω power resistor in the (+) line.

Battery charging cable wiring, when looking into the power socket on the PSU.

Technical specifications
Valves
  • Receiver
    1 x 6J6, 2 x 9001, 1 x OB2
  • Transmitter
    1 x 6AQ5
  • Metering Unit
    1 x 6X4
Dimensions
  • Power Supply
    15 x 13.5 x 5.5 cm
  • Receiver
    15 x 13.5 x 5.5 cm
  • Transmitter
    8 x 13.5 x 5.5 cm
  • Metering Unit
    8 x 13.5 x 5.5 cm
Documentation
  1. Betriebs- und Fehlersuchanleitung für 12 WG
    Operating manual and trouble shooting guide (German).
    OG 1 date unknown but probably 1953. 17 pages.

  2. Inbetriebsnahme des 12 WG 2
    12WG Commissioning guide (German).
    OG 1 date unknown but probably 1953. 1 page.
  1. OG = Organisation Gehlen (Gehlen Organization) → Wikipedia
  2. Document kindly supplied by Jim Meyer [6].

References
  1. Detlev Vreisleben, Information about the 12-WG
    Personal correspondence. August 2015.

  2. Bundesnachrichtendienst (BND), Vitrine 11, Typ 12 WG
    Si 90/1219. 11 September 2006. Kindly supplied by [1].

  3. Louis Meulstee, 12 WG
    Wireless for the Warrior - Volume 4, Supplement, Chapter 53-1.
    Retrieved May 2016.

  4. Nico van Dongen, Photographs of 12WG/M Metering Unit interior
    Obtained May 2016. Reproduced here by kind permission.

  5. Günter Hütter, Reconstruction of the 12WG/M enclosure
    July 2016.

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

  7. Jan Bury, Operation Stonka. An Ultimate Deception Spy Game
    Cryptologia, Volume 35, 2011, Issue 4.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
© Crypto Museum. Last changed: Saturday, 01 October 2016 - 06:33 CET.
Click for homepage