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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].
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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, 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.
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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].
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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.
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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.
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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 increasingly had to deal with clandestine radio
stations. These were often agents that were dropped over occupied territory
by the Allied Forces, but there were also resistance groups within
Germany itself. In order to locate and catch such clandestine stations, a
series of mobile intercept and radio direction finding (RDF)
solutions were developed. The most common of these were mobile RDF stations
disguised as laundry trucks or delivery vehicles.
As 'alien' vehicles were easily spotted in those days — there were hardly
any cars on the road — portable solutions
were developed that could be used in the vicinity of the transmitter.
A good example is the Wien suitcase receiver.
It would be carried on foot, by an 'innocent' traveller.
The most perfect solution however, was the body-worn Gürtelpeiler,
which was completely
concealed under the operator's clothing, attracting no attention whatsoever.
The operator could 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 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 (German: Rahmen)
that is carried around the neck.
It is a direction sensitive loop made from 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 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.
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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 service,
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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© Crypto Museum. Created: Sunday 18 March 2012. Last changed: Wednesday, 30 September 2020 - 14:22 CET.
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![Gürtelpeiler mounted on the chest of an operator [3]](img/coat_open_full.jpg)
![Gürtelpeiler circuit diagram [3]](img/schema_full.jpg)