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Gürtelpeiler
Portable Radio Direction Finder - wanted item

Gürtelpeiler, or Gürtelpeilgerät was a portable radio direction finder (RDF), used during WWII by the German secret services (e.g. Abwehr, Sicherheitsdienst and Ordnungspolizei) to track down clandestine (resistance) transmitters operating on German (controlled) territories. Developed in 1942 by the Nachrichten-Erprobungs- und Abnahmestelle (Communication Development Section) of the German Ordnungspolizei [1] as FuG.P.c, and built by Kapsch in Wien (Vienna, Austria) [2].

Like its suitcase-based predecessors, such as the Wien and Kapsch receivers, the Gürtelpeiler was intended for concealed operation. It was however, the first intercept receiver that was shaped to the body and could be carried under the operator's clothing, allowing it to be used on foot, driving a bicycle, or even when skiing [3].

The image on the right shows an original Gürtelpeiler [4] in the upside-down position, so that the text is readable. The receiver has two antenna's: (1) a fixed reference-antenna and (2) a loop-antenna that is carried around the neck.
  
Original Gürtelpeiler

Later portable direction finders and intercept receivers, such as the post-war Telefunken PE-484, and the Cold War Russian intercept receivers Filin, Soyka and Sinitsa, are clearly inspired on the design of the Austrian Kapsch Gürtelpeiler. They can all be hidden under the operator's clothing.

Very few Gürtelpeilers have survived and are now in private collections. In fact they are so rare, that the makers of the movie Soldaat van Oranje (Soldier of Orange), about the Dutch Resistance during WWII, used the post-war Telefunken PE-484 in a scene where a Dutch Resistance radio station is located. We are indebted to Austrian collector Günter Hütter [4] for granting access to a genuine Gürtelpeiler and for supplying a copy of the book Die Funkpeilung der Kurzen Wellen [3].

Wooden storage case for Gürtelpeiler Original Gürtelpeiler Rear-view of the Gürtelpeiler (body-side) Perspective view of the Gürtelpeiler Gürtelpeiler with antenna and connections
Storage case
When not it use, the Gürtelpeiler was stored in a wooden transit case, together with a range of accessories, spare parts and consumables. Various solutions were suggested, such as common suitcases, but in most cases the unit was stored in the purpose-built wooden transport case shown below. The case was constructed in such a way that all items were easily accessible.

The wooden storage had a large hinged lid at the front and a smaller one at the top. It had various compartments that allowed all items, including the main unit, to be stored neatly.

The receiver itself is stored in the largest compartment at the bottom. A series of spare valves (tubes) is stored in a narrow section at the top. The image on the right shows a typical wooden storage case for the Gürtelpeiler. The spare valves are clearly visible at the top. As they are all of the plug-in type, they can easily be swapped in the field, reducing repair times.
  
Close-up of the top section of the storage case

The following items were stored in the case [3]:

  • 1 Main unit, complete with valves (tubes), coils and batteries
  • 18 Spare coils
  • 1 Wooden box with 20 coils
  • 1 Set of spare valves (5 x 2.4 P-700 and 2 x 2.4 H-300)
  • 6 Spare transformers 2.4V/1.25mA
  • 10 Spare flashlight batteries of 4.5V each
  • 2 Charge Resistors (9 and 24 Ohm)
  • 4 Charge Cables (each with an Anode-plug and Battery-clip)
  • 6 Charge Valves
  • 1 Headphones
  • 1 Earphones
  • 1 Wrist watch-style meter (field-strength indicator)
Wooden storage case for Gürtelpeiler Empty storage case Storage case with front and top lid open Close-up of the top section of the storage case Close-up of the spare valves
Operation
During WWII, the Germans were increasingly dealing with clandestine radio stations. These were often agents that were dropped by the Allied forces (e.g. Great Britain) on occupied territory, but also resistance groups within Germany itself. In order to track down such clandestine radio stations, a series of radio direction finding (RDF) solutions were developed. The most common of these were mobile RDF station disguised as laundry trucks.

As 'strange' vehicles were easily spotted in those days, portable solutions were developed that could be used in the vicinity of the transmitter. Once example is the Wien suitcase receiver. It would be carried on foot, by an 'innocent' traveller. The most perfect solution however, was the Gürtelpeiler, which was completely concealed under the operator's clothing, attracting no attention whatsoever. The operator would simply walk through the neightbourhood and turn his body to establish the direction of the transmitter.

Gürtelpeiler mounted on the chest of an operator [3] Same operator with his coat closed. The Gürtelpeiler is now concealed.

The images above show how the Gürtelpeiler was used. The leftmost image shows the receiver on the belly of the operator, with the antenna around his neck. The image on the right shows the same man with his coat closed. The receiver is now hardly noticable. Apart from standard head­phones, the receiver came with a much smaller earpiece as well; the co-called Lilliputhörer. A signal-strength meter, disguised as a watch and carried on the wrist, was used as an indicator.

The Gürtelpeiler came with two antennas that were selectable with a switch on the receiver's body. One antenna is a simple rod (Stab) that can be carried either upwards or downwards. It is used in close proximity of the transmitter (e.g. inside a building). The main antenna is a loop (Rahmen) that is carried around the neck. The direction sensitive loop consists of a coaxial cable of which the shield has a gap in the middle.

The Gürtelpeiler was suitable for ranges up to 3 km, depending on the situation (city, rural, etc.), but was most effective within a radius of 1 km around the (clandestine) transmitter. Its sensitivity is equal to that of the tripod-based R-30 (Kapsch) direction finder.

Circuit diagram
The Gürtelpeiler is a superheterodyne receiver, build around 7 valves (5 x RV2.4 P-700 and 2 x RV2.4 H-300). The circuit diagram of the receiver is given below. At the left are the antennas, with a switch for selection between the search antenna (rod) and the directive antenna (loop). The signal is first amplified (Rö1) and then mixed (Rö2) with the signal from the oscillator (Rö7).

Gürtelpeiler circuit diagram [3]

The next two valves (Rö3 and Rö4) are two IF stages, followed by a regenerative circuit (Rö5) and finally an LF amplifier (Rö6) that delivers the audio signal into 4000 Ohm headphones. The self-regenerative circuit (Rö5) was rather popular between 1920 and WWII [5]. It is commonly known as Autodyne. In German it is called Audion [6]. The last stage (Rö6) is the audio amplifier.

The Gürtelpeiler was suitable for frequencies between 3 and 20 MHz (15-100m), divided over 10 bands, each of which was selected by using two plug-in coils. One coil was used for the oscillator (Rö7). It allowed coarse tuning at the desired frequency. The other coil was part of the 1st stage (Rö1) and was used for fine tuning.

Wanted item
At present, Crypto Museum does not have a genuine Gürtelpeiler in its collection. If you have such a device available, or if you know of a sample that might be available, please contact us.

References
  1. Louis Meulstee, RDF Receiver 'Gürtelpeilgerät' FuG.P.c
    Wireless for the Warrier. Volume 4. September 2004. ISBN 0952063-36-0.

  2. Arthur Bauer, Some aspects of the German military 'Abwehr' wireless service,
    during the course of World War Two.
    Diemen (Netherlands), 15 September 2003. pp. 13-14.

  3. Hauptamt Ordnungspolizei, Die Funkpeilung der Kurzen Wellen. 1. Teil
    Radio Direction Finding on the Short Wave Bands. Part 1 (German).
    Chapter II-5, Das Gürtelpeilgerät. Berlin (Germany), 1943. pp. 94-102.

  4. Günter Hütter, Owner of the Gürtelpeiler featured on this page.
    Crypto Museum, Austria, June 2008.

  5. Wikipedia, Regenerative circuit
    Retrieved March 2012.

  6. Wikipedia, Audion
    Retrieved March 2012.
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© Crypto Museum. Created: Sunday 18 March 2012. Last changed: Wednesday, 22 March 2017 - 07:04 CET.
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