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FBA Peiler
Nahfeldausforschungsgerät
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Near-field direction finder
The FBA-Peiler 1 , or Nahfeldausforschungsgerät, was a portable near-field
direction finder, developed in the early 1960s by the
Fernmelde Betriebsamt (FBA) in Vienna, at the time part of the
Austrian state-owned telecom operator ÖPT.
The device was intended for finding radio and television interference (QRM)
and clandestine transmitters, such as spy radios
and radio bugs.
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The device has a frequency span of 3 - 145 MHz and consists of a
small hand-held receiver (the direction finder)
and 15 frequency plug-in units.
The actual receiver measures 9 x 17 x 3 cm and is housed in a white plastic
case, similar to a 1960s portable radio. It is fully self-contained
in that it is battery powered, has a wire antenna and a leather
carrying strap with a wired crystal earphone that delivers the audio
to the operator.
The entire kit is nicely packed in a
robust metal carrying case
with a leather grip at the front.
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The case of the FBA-Peiler is constructed in such a way that the device can
easily be hidden under the operator's clothing [1].
All one has to do is select the appropriate coil unit (i.e. frequency plug-in)
and adjust the variable capacitor on the receiver to the desired frequency.
The device is suitable for direct reception
of AM signals and FM signals that have a sufficient AM-component.
In addition, a 1000 Hz tone can be injected directly at the receiver's
input, so that the receiver can be used for the detection of transmitters
with AM or FM modulation, or no modulation at all. After detection, this produces a 1000 Hz tone of which the strength varies with the strength of
the intercepted signal. This feature is extremely useful when in close
proximity of the transmitter.
It is currently unknown how many FBA direction finders were built,
but given the quality of the cases, the building style of the electronics,
the presentation of the manual and the known serial numbers (199, 303),
it seems reasonable to assume that it was built in small quantities,
probably a few hundreds. As they were only
used by special services and agencies, not many units have survived
once the receivers were decomissioned.
At present, only three surviving units are known.
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Peiler is the German word for Direction Finder.
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Controlling the receiver is pretty straightforward. All controls are on
the left side of the device. After installing the
selected frequency plug-in coil
on top of the receiver,
the unit is turned on by turning the sensitivity adjustment away from
its null-position (a click indicates that the receiver is switched on).
The earpiece should now produce noise and the tuning knob is used
to select the desired frequency. A slide switch allows the 1000 Hz
generator to be activated (slide upwards).
In close proximity of a transmitter, the plug-in coils act as antennas.
When further away, an external wire antenna can be connected to the side
of the coil unit. When homing in on the transmitter, the optional 1000 Hz
tone can be used for guidance. By reducing the sensitivity of the receiver
each time you get closer to the transmitter, locating the transmitter will
be very easy.
The receiver is designed to be worn on the left side of the body, with the
leather strap over the right shoulder. This way the controls are facing
towards the front and can easily be manipulated with the right hand. A simple
wire is used as antenna, so that it can be hidden inside the clothing.
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- 100-145 MHz
- 75-100 MHz
- 50-75MHz
- 36-50 MHz
- 28-36 MHz
- 24-28 MHz
- 19-24 MHz
- 15-19 MHz
- 12-15 MHz
- 9.5-12 MHz
- 8-9.5 MHz
- 6-8 MHz
- 5-6 MHz
- 4-5 MHz
- 3-4 MHz
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A standard 4.5 flat-pack battery is used to power the device.
This is roughly the size of three 1.5V AA-size cells. The image
on the right shows the actual receiver, which resides in the upper
section of the case. At the top are the two terminals for the frequency
plug-in unit. They are placed assymetrically, so that the coil plug-in
can not be inserted the wrong way around.
At the left side are the sensitivity potentiometer and the tuning
capacitor. The three OC75 germanium transistors of the 3-stage
amplifier are 'floating' side-by-side at the centre.
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The circuit diagram of the receiver is surprisingly simple.
At the top left is the tuned circuit that is responsible for tuning to
the desired frequency. It consists of a
removable coil and an adjustable
capacitor. The optional 1000 Hz homing signal (T1) is injected via a diode (D1)
directly to the tuned circuit, thereby modulating the incoming signal in AM.
After detection (D2), a 3-stage amplifier (T2, T3 and T4) delivers just
enough signal to drive a crystal earphone.
The circuit is powered by a standard 4.5V flat battery and takes
just 8mA even with the 1000 Hz generator on.
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FBA-Peiler (Nahfeldforschungsgerät) circuit diagram [1]
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The FBP-Peiler is supplied in a professional
sturdy green hammerite metal carrying case
with two locks and a leather carrying grip at the front.
Inside the top lid is the circuit diagram
with some directions on how to use the receiver,
plus a list of the frequencies covered by each plug-in unit.
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The bottom part of the case contains a pre-shaped polystyrene (PS)
block with velvet lining. A large bay is reserved for the actual
direction finder and has a storage area for the leather carrying
strap with the earphone underneath it.
The 15 frequency plug-in coils are each labelled with a letter of
the alphabet (A-O). They are nicely arranged around the receiver,
each with their two contact pins mating with two holes in the PS bottom.
The image on the right shows the interior of the carrying case after
the receiver has been removed. The earphone is still visible.
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Also visible in the storage area is a
short piece of wire with a banana-plug
at the end. It is used as a concealed antenna and should be connected at the
side of the frequency plug-in. The length of the antenna is relatively short
compared to the wave length, which reduces the sensitivity of the receiver,
especially below 6 MHz [2]. In practice this was not considered a problem
however.
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Transmitters operating on such low frequencies
generally use a lot of transmission power. Besides, the device was intended
for use in the near-field (at close proximity of the transmitter)
in which case the antenna length doesn't matter.
Because of the small quantities in which the receiver was built,
it doesn't have an official model name or number. Instead it was called
FBA-Peiler or Nahfeldausforschungsgerät.
Each device does have a serial number however,
plus the abbreviation of the department (Stelle) that used it.
The image on the right shows the tag.
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According to the tag,
it was used by the 'FU' department of the
Fernmeldebetriebsamt (FBA) in Klagenfurt, and has serial number 303.
Another FBA-Peiler, from the collection of Günter Hütter in Austria [4]
carries a slightly different tag.
It has serial number 199 and
was apparently used by the 'FÜV' department of the Fernmeldebetriebsamt (FBA)
in Innsbruck (Tirol, Austria).
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FBA
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Fermelde Betriebsamt
Former Austrian Communications Service, reponsible for the deployment, operation,
exploitation and enforcement of telephone and telegraph lines. Part of the
Austrian state-owned Post and Telegraph service ÖPT.
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ÖPT
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Österreichische Post- und Telegraphenverwaltung
Former Austrian state-owned Post and Telegraph service [3].
Known as PTV and ÖPT.
(Wikipedia)
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© Crypto Museum. Last changed: Tuesday, 21 August 2018 - 05:27 CET.
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