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Short-wave converter
The BND SW Converter was a minature crystal-operated short-wave (SW)
converter, introduced in the late 1950s by the
West German intelligence
service BND,
for use by agents operating in the
DDR (East Germany).
The converter was a replacement for the
OG/BND SW Receiver,
and turned an ordinary domestic medium-wave (MW) broadcast radio
into a clandestine SW receiver
[1].
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A major shortcoming of the BND SW Converter was the rather strong signal
that was produced by its crystal-operated local oscillator (LO), that could
easily be detected with appropriate
direction finding (DF) equipment, and
made the unit liable to detection and discovery by the
DDR agencies.
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The photographs below were kindly supplied by collector Detlev Vreisleben
from Germany [2], and shows that some BND Converters were supplied with
a dummy battery with two wires, that allowed an external DC supply
(3 to 4.5V) to be used as an alternative to the internal 3V battery.
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The BND Converter is an extremely simple device that does not have many
connections and controls, as illustrated in the diagram below.
The unit is powered by an internal 3V battery that can (optionally)
be replaced by a dummy, in order to power it by an external source,
such as a 4.5V dry battery. It is
switched ON by inserting a plug in the
antenna socket
at the other side.
The output of the converter is available at the
3.5 mm jack socket at the
front, that should be connected to the antenna and ground terminals of the
MW receiver, using the supplied cable.
The crystal for the desired channel should be installed in the grey socket
at the top, whilst the circular grey dial should be set to a particular number,
as listed in the frequency/time table (see below).
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The BND SW Converter was introduced at a time when the
Cold War tension
between East and West had reached the point where East Berlin was about to
be separated from West Berlin and/or the borders were about to be closed
hermetically. In the past, the BND
had supplied a miniature SW receiver
to its agents in the DDR, but these were only suitable for the
reception of messages in morse code
(CW) and, hence, required the operator
to be an experienced radio telegraphist or a radio HAM. Furthermore, the
posession of a SW receiver was considered illegal in the DDR.
In order to overcome these problems, the BND started distributing the
miniature SW Converter, which allowed an ordinary MW broadcast receiver
to be used for the reception of verbal messages in the SW band. Initially it
was used in combination with valve-based receivers like the Weimar 4680
and the WWII leftovers like the Volksempfänger (people's radio),
but later it was also used with the first transistorized portable radios
like Sternchen when these became widely available.
The agent was supplied with a frequency/time table such as the one shown
above. He or she was required to listen to the specified channel
at specific times of a particular day, each week. To ensure that
the agent had found the correct frequency, each broadcast started
with a particular melody that acted as the station's identification.
Only messages that started with the
agent's callsign (RUF-NR) had to be taken down. All messages were coded
one-on-one, which means that they were coded
differently for each agent, using the unbreakable
One-Time Pad (OTP) code
[C].
Messages were sent in groups of 5 digits, separated by a space, eg. 35436.
The first group was the message indicator (Kenngruppe) and identified
which one-time pad
had to be used. The agent wrote the OTP series above the received digits
and then subtracted the two (modulo 10). The resulting digits were translated
into plain text by means of the table above. This particular translation table
is known as DEIN STAR.
Full decoding instructions
can be found here
[C].
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The converter was crystal-operated, and two channels in the Short Wave
(SW) radio band are known to have been used for this purpose by the BND:
DFC37 (3370 kHz) and DFD21 (4010 kHz). The block diagram below shows the basic
operation of the converter, which is known as a down converter.
This means that the crystal has to be 1500 kHz higher than the
reception frequency.
The circuit diagram below shows the rather simple construction of the
BND converter. At the bottom is a crystal oscillator built around an OC170
transistor. The output of this Local Oscillator (LO) is mixed with the
received signal in another OC170, and presented at the top right (Output).
At the top left is the 3V battery which is connected with its (+) terminal
to ground. The device is turned ON by inserting a banana plug in the
antenna socket of the device. Note that in some versions, the battery
could be replaced by a wired dummy
for connection to an external source.
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The BND Converter was suitable for common crystals with a pin distance of
12.5 mm. The socket on top of the device accepts crystals with thick and thin
pins.
As the device is a down converter, the crystal frequency has to be
chosen 1500 kHz higher than the desired frequency. For further details,
please refer to the frequency table below.
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As the Converter was used by agents operating in the hostile environment
of the suppressive DDR regime, it
was of the utmost importance to hide it properly, so that it would
not be found by the authorities during an unexpected search.
The image on the right shows one of the most beautiful concealments
that were used for the BND Converter, which is constructed from an
operational 'Liliput' kitchen boiler
(German: Durchlauferhitzer)
of the era. The Converter itself is stored at the centre, whilst the
crystals and the other accessories are stored at the top.
It was discovered by the East-German MfS 1 (Stasi) and was
documented in one of the reports of the Stasi's HA-IX department [D].
➤ Liliput promo
➤ Liliput concealment
➤ Liliput close-up
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The best possible concealments are often the most common objects that are used
every day, and that can be hidden in plain sight, such as the thermos
shown at the right. It consists of a glass bubble that
is mounted inside a cylindrical metal enclosure. By making the glass bubble
shorter than normal, an empty space becomes available at the bottom of the
enclosure, which makes it a perfect concealment container.
The image on the right shows that the Converter and all of its accessories
and paperwork, could be hidden inside the unobtrusive thermos.
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The image on the right shows how the
West-German intelligence service BND
and the American CIA
brought the Converter into the DDR. In this case it was
concealed in a children's toy, a wooden train,
but other concealments, such as DDR vegetable cans, were used as well.
The image on the right was shown in the East German newspaper Neues
Deutschland on 6 September 1959, in a
report about four Western agents
that had been traced and convicted in the DDR: Erich Keimling (38),
Gisela Gebhardt (26), Franz Brehmer (37) and Walter Huth (54) [4].
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Another beautiful concealment which was used by Western agents inside the DDR,
is described in Stasi documents now held by the BStU [G]. In the event,
the agent had a pair of hollowed-out wooden book supports that contained the
BND Converter, its accessories and the paperwork.
The two concealments were found on his bookshelf, acting as inconspicuous
book supports. Nevertheless they were discovered by the Stasi and became part
of their internal 'museum', as proof of capitalistic subversive activities [G].
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MfS = Ministerium fur Staatssicherheit (Ministry for State
Security), also known as Staatssicherheit, or Stasi.
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The BND converter featured on this page is not particularly well-built,
and is certainly not of the famous German manufacturing quality. Instead,
it seems to have been designed and built in a rush, probably due to the
situation in the DDR.
In the image on the right, an alternative design is shown,
that was probably
introduced later, and that is more in line with the general German
manufacturing standards. As the knob on the device was also used on the later
FSK-modulator of the SP-15 spy radio set,
we think it was made by either
H. Pfitzner or Wandel & Goltermann.
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An alternative SW converter, that was distributed by the British intelligence
agencies, is shown in the image on the right. It is similar in operation to
the BND Converter but is somewhat larger. It is shown here with two crystals
at its top left.
Like the other converters, quite of few of these were discovered by the DDR's
secret service, the Stasi, and are described in various reports.
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The BND Converter is housed in a black metal enclosure that measures
65 x 63 x 28 mm. The case consists of two shells of which the lower one
is held in place by a large bolt at the bottom. After removing this bolt
with a suitable screwdriver or a coin, the interior can be accessed.
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Inside the case is a brow pertinax board with rounded corners. It has
components fitted at both sides, but only the bottom side is visible
after opening the case. At the centre is a large adjustable capacitor,
which is made in Japan.
At the front left is a socket for connection of the antenna. When plugging
a banana plug into this socket, a switch at the other side of the board
is engaged and switches on the battery. The device is powered by a 3V dry
battery cell, that fits the battery holder at the top right. Note that the
holder might be damaged by leaking batteries.
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The brown pertinax board is held in place by three screws, two of which
are located at either end of the crystal socket and can be removed easily.
The third screw is located under the grey knob at the top panel, and
requires the knob to be removed first. The board should then be loosened.
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After removing the washer from the 3.5 mm jack socket, the pertinax
board can be removed from the case. Be careful not to damage any of the
extremely thin wires to the coils at either side.
The image on the right shows the top side of the board, which is usually
hidden from view. At the right is the grey crystal socket, whilst the
jack socket (the output) is visible at the left. At the bottom right is
the rather long power switch, which is controlled by the banana socket
at the other side. Power is automatically turned ON as soon as the
antenna's banana plug is plugged in.
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Although the BND Converter featured here is in very good condition,
especially considering its age, it should be obvious that it was designed
and built in a rush, probably under pressure of the political situation in
the DDR at the time. It is by no means built to the high quality
standards that the Germans are famous for.
This was improved in a later design,
of which the name is unknown.
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Type Crystal operated Input 3 - 6 MHz Output 1500 kHz ± 50 kHz (200 metres) Circuit oscillator, mixer (2 x OC170 transistor) Power 3V dry battery
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The BND Converter is a so-called down converter with an output
frequency of 1500 kHz, which means that the crystal frequency has to be
chosen 1500 kHz above the desired reception frequency. Two channels were
commonly used, known as 1 and 2. If interference was expected from
breakthrough of broadcast stations on 1500 kHz (i.e. the output frequency),
alternative crystals (1A and 2A) could be used, which resulted in a slightly
different output frequency.
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#
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Name
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Frequency
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Crystal
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Output
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Remark
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1
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DFC 37
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3370 kHz
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4870.00 kHz
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1500.00 kHz
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1A
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DFC 37
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3370 kHz
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4830.01 kHz
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1460.01 kHz
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Backup
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2
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DFD 21
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4410 kHz
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5510.00 kHz
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1500.00 kHz
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2A
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DFD 21
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4410 kHz
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5537.96 kHz
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1527.96 kHz
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Backup
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Document kindly provided by Detlev Vreisleben [2].
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- Louis Meulstee, BND SW Converter
Wireless for the Warrior - Volume 4, Supplement, Chapter 34-1.
Retrieved March 2017.
- Detlev Vreisleben, BND Converter documentation
Retrieved December 2014, March 2017.
- Len Scott, R Gerald Hughes, Intelligence, Crises and Security
Prospects and Retrospects. The Secret Service and the Berlin Wall.
2008, Routledge. pp. 186-187.
- ...und dann bekam ich den Decknamen 'König'
...and then I was given the covername 'King' (German).
Neues Deutschland (Newspaper). 6 September 1959. 1
- Bundesarchiv, Photograph of woman with Liliput kitchen boiler
Image 183-28773-0004. Retrieved March 2017 via Wikipedia.
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Document kindly provided by Detlev Vreisleben [2].
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© Crypto Museum. Created: Thursday 02 March 2017. Last changed: Tuesday, 24 December 2019 - 22:25 CET.
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![Liliput miniature in-line kitchen boiler promo. Bundesarchiv [5].](img/liliput_thumb.jpg "image # liliput_large.jpg"){kind=small}
![Liliput miniature in-line kitchen boiler promo. Bundesarchiv [5].](img/liliput_large.jpg)
