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Portable Radio Direction Finder
- Wanted item
The Gürtelpeiler, or Gürtelpeilgerät was a portable
radio direction finder (RDF) that was used during WWII by the German
secret services (e.g. Abwehr, Sicherheitsdienst, Ordnungspolizei)
to track down clandestine (resistance) transmitters operating on
German (controlled) territories. It was developed in 1942 by the
Nachrichten-Erprobungs- und Abnahmestelle
(Communication Development Section) of the German Ornungspolizei [1]
as Fu G P. c.
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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.
It could be used on foot, on 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 finding-antenna
and (2) a loop-antenna that is carried around the neck.
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Not many Gürtelpeilers have survived the war and only very few are
known to be held in private collections. They are in fact 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 they track down
a Dutch Resistance radio station. We are indebted to Günter Hütter
in Austria [4] for giving us access to a genuine Gürtelpeiler and
supplying a copy of the book Die Funkpeilung der Kurzen Wellen [3].
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 German Gürtelpeiler. They can all be hidden under the operator's
clothing.
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When unused, the Gürtelpeiler was stored in a transit case, together with
its accessories, spare parts and consumables.
Various solutions were suggested, such as common suitcases,
but in most cases the unit was stored in a purpose-built wooden transport case.
The case was constructed in such a way that all items were safely and
neatly packed.
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The wooden storage had a large 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.
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The following items were stored in the case [3]:
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- 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)
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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.
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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 wrist watch, was used as a visual
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.
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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).
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 Gürtelpeiler was suitable for frequencies between 3 and 20 MHz
(15-100m), divided over 10 ranges that were selected by plug-in
coils. Two coils were used for each range. 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.
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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.
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- Louis Meulstee, RDF Receiver 'Gürtelpeilgerät' FuG.P.c
Wireless for the Warrier. Volume 4. September 2004. ISBN 0952063-36-0.
- Arthur Bauer, Some aspects of the German military 'Abwehr' wireless serice,
during the course of World War Two.
Diemen (Netherlands), 15 September 2003. pp. 13-14.
- 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.
- Günter Hütter, Owner of the Gürtelpeiler featured on this page.
Crypto Museum, Austria, June 2008.
- Wikipedia, Regenerative circuit
Retrieved March 2012.
- Wikipedia, Audion
Retrieved March 2012.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Tuesday, 18 March 2014 - 13:41 CET
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![Gürtelpeiler mounted on the chest of an operator [3]](img/coat_open_small.jpg "Gürtelpeiler mounted on the chest of an operator [3]")
![Gürtelpeiler circuit diagram [3]](img/schema_full.jpg "Gürtelpeiler circuit diagram [3]")