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Bugs NERA NATO MI6
The device works at a frequency around 3.4 GHz and consists of a pyramidal feed
horn and a wave guide with a detector diode. The signal from the
detector is amplified and fed to a pair of
headphones and (optionally) to a recorder.
The VR-2 is powered by a regular 4.5V battery, that is installed inside the
grip at the bottom. Inside the wave guide is a
dielectic taper that
focusses the microwave beam in the same way as a lens focusses light.
The axial position of the dielectric taper can be adjusted with a
plunjer at the rear.
This also alters the frequency slightly.
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At the side of the battery compartment
is a 9-digit code (-25-101-1890), which is basically a NATO Stock Number
(NSN) of which the first four digits are missing. 2 The complete
number is NSN 5865-25-101-1890, which is described in the NSN database as
DETECTING SET, RADAR. It's group code (5865) reveals that it belongs to the
category of Electronic Countermeasures (ECM), Counter-Countermeasures (ECCM)
and Quick Reaction Capability equipment (QRC). This group code was also
used as a camouflage for dual-use equipment of which even the people on the
production line were not supposed to know the true purpose.
It is known that the device shown here was used in Germany between 1984
and 1989 by British intelligence service MI6 [1].
It is currently unknown when the VR-2/B was developed, but date codes
on the internal parts indicate that it was built in late 1962 or early 1963.
It is also likely that it was part of a series of devices that were developed
between 1952 and 1980 — probably with help from the
Norwegian Defence Research Establishment (FFI) —
in response to the discovery in 1952 of a similar device at the
residence of the American Ambassador in Moscow, which became
known as the Thing [4].
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According to the NSN database, the device was made for the German market.
The device shown here was used in Germany by the British intelligence service
MI6 and has German text on its control panel. This
was probably done to hide its real use by the British [1].
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Without the 4-digit prefix, an NSN is known as a National Item
Identification Number (NIIN) [7]. It uniquely identifies the item.
The 4-digit prefix only specifies the Supply Classification Group.
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PLEASE HELP —
At present, Crypto Museum only has a VR-2/B receiver in its collection.
We are still looking for the activation transmitter and for the actual bug —
the passive microphone. If you have additional information,
documentation or, better, the actual hardware, please contact us,
so that we can expand this page.
The diagram below shows how the devices were used. At the bottom left is
the activation transmitter (1) which comprises a klystron oscillator
and a feed horn. It illuminates the target from a distance of 500-600 metres
with a strong continuous wave (CW) microwave signal of a specific frequency.
A portion of this signal hits the concealed bug — a passive microphone (2) —
that is hidden in the target area. If the incident illumination frequency is
the same as the microphone's resonant frequency, it will cause the microphone to
resonate and (re)emit some of the energy.
The signal emitted by the bug has the same frequency as the illumination
signal, but is Amplitude Modulated (AM) with the sound picked up in the room
where the bug is hidden. It is intercepted by the VR-2 receiver (3),
which can be up to 1 km away.
Note that transmitter and receiver are at different locations to avoid
spillover from the transmitter into the receiver. They are typically placed
at 90° angles.
Note that such distances were possible as there were virtually no other
signals or sources of interference in the 3-4 GHz band and the time.
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The activation transmitter – used to illuminate the target –
is built around a klystron oscillator. It is housed in a rectangular enclosure
inside which the feed horn, the klystron, the HT power circuits, a timer
and the batteries are housed.
The timer was used for unmanned operation and allowed the illumination signal
to be transmitted only during specific times of the day. At the centre is the
klystron, which is used as a free-running oscillator. It has a knob by means of
which the frequency can be tuned somewhat.
The device is powered either by the internal batteries or by means of the external
12V DC power supply unit, which was stowed inside the top lid.
The transmitter is currently missing from our collection. The image on the
right shows an educated guess of what it looked like, based on the
recollections of an eye witness [1].
No photograph available
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The exact operation and construction of the actual bug — the passive element (PE) —
is currently unknown, and no surviving specimen has turned up so far.
From the description of a former MI6 operative however, we were able to
create the educated guess shown in the diagram below [1]. The device is
concealed inside a plastic cigar tube. As soon as the screw cap is
removed from the cigar tube, a spring ensures that the microphone end of
the device is raised above the tube.
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Educated guess of the construction of the passive element
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The microphone consists of a thin plastic cone that is suspended
from the top of a cylindrical frame. At the bottom of the cone is a metal
needle that enters a resonant unit. Any sound in the target area causes the
cone to vibrate and the needle to move in and out of the resonant unit.
Note that this construction makes the microphone extremely sensitive to
other types of vibration, such as walking through the room, slamming a door,
or placing coffee cups on the table top.
It is currently unclear whether the actual device is a resonant cavity –
like the original Russian device – or an open dipole with a
capacitive load. In the former case, the moving needle alters the volume of
the cavity. In the latter case, the needle extends through the upper arm of
the dipole, half way into the lower arm. Its movement alters the capacity
between the two arms of the dipole.
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Possible construction of the passive element (cross section of the dipole)
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The microphone is constructed in such a way that it can be used in
radial as well as axial mode. In most cases the PE was used in vertical
position — it was typically hidden inside a table leg — in which case
the microphone is used in radial mode and sound enters it from the side(s).
In this mode, the microphone is omni-directional.
The diagram below shows how it was usually hidden:
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Passive element hidden inside a 1" hole in a table leg
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Note that the plastic cigar tube was not removed (only the cap).
It was also possible to use the PE as a contact microphone, in which
case the open end of the cone was attached to, say, a wall or a floor board.
In that case, the microphone is used in axial mode and is uni-directional,
but the sound quality is not as good as with a real contact microphone,
such as the CIA's SWM-25.
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Passive microphone used in axial mode (as contact microphone)
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In September 1952, a hitherto unknown type of
covert listening device (bug) was discovered at the residence
of the American Ambassador in Moscow. It was hidden inside a wooden carving of
the Great Seal of the United States that hang on the wall behind the
ambassador's desk.
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The carving had been given by the Russians in August 1945, to commemorate
the close friendship between the United States and the Soviet Union (USSR) during World War II (WWII) and the
subsequent defeat of Nazi Germany.
For more than seven years it had provided the Russians with the most sensitive
first-class intelligence.
The mysterious bug, which became known as The Great Seal Bug,
didn't contain any electronic parts and did not have its own power source.
As it was initially unclear how it worked, it soon became known by its nickname
— the Thing [4].
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Immediately after the discovery of the Thing, the device was
brought to the US, where it was investigated by the
Federal Bureau of Investigation (FBI)
and the Naval Research Laboratory (NRL). From several publications,
such as Peter Wright's book Spy Catcher [2]
and David Wise's book Molehunt [3], it is known that part of the
initial investigation was carried out abroad, including in the UK and the
Netherlands. It is also known that the CIA conducted its own investigation.
The final FBI/NRL report,
that was released on 1 December 1952
(declassified in 2019), contains a
detailed drawing of the bug
in which the dimension are given in centimetres rather than inches, which
reveals the involvement of a metric country [5].
The most likely candidates are the Norway and the Netherlands, both of which had
strong ties with the US at the time, and had the required technological
expertise. The Netherlands can be ruled out, as they were already involved in
the secret EASYCHAIR research program of the CIA, leaving
Norway as the most likely FBI candidate.
It is possible that the FBI research was partially carried
out at the Norwegian Defence Research Establishment
(FFI) in Bergen (Norway), which had been established shortly after WWII
in 1946. Many of
its scientists and engineers had escaped to the UK during the war, where
they worked on technological developments in the field of radio and radar.
The first post-war Norwegian radar systems were developed at the FFI and were
manufactured by NERA, which was co-located.
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The device featured here, was used in Germany by the
British intelligence service MI6
against various types of targets, both foreign and domestic.
This involved breaking into offices and homes when the target area was
abandoned, installing the bug (the PE), removing any traces of the
operation, leaving the target area and testing the bug. On the way to
the target area, the MI6 operative carried the PE in a cigar box
filled with real cigars, just in case he was ever checked.
He would then break into the building by means of
surreptitious entry,
inspect the target area and decide where to hide the PE. In most
cases it was hidden inside a table leg or inside a heavy piece of
furniture. The operative would partly disassemble a table or desk,
drill a hole of the desired diameter and depth, remove the cap from
the PE and install it in the freshly drilled hole.
The table was then reassembled and all traces of the operation (such
as wood chips and dust from the drilling) were removed. Note that it
was necessary to either drill an additional hole for the PE's
microphone, or leave enough of an air gap between the top of the table
leg and the table top, to allow sound to reach the microphone.
An example of a domestic target of the mid-1980s is KUKA Wehrtechnik GmbH in
Augsburg (Germany) [8]. From 1981 onwards, KUKA was one of the suppliers of
anti-aircraft equipment to the Germany Army and NATO. To ensure that KUKA
stayed within NATO guidelines and did not sell its technology to proscribed
countries, a bug was planted in its office [1]. KUKA Wehrtechnik was
sold in 1999 to Rheinmetall [8].
The remainder of KUKA — in particular the industrial robot business —
was bought in 2016 by the Chinese company Midea Group [8].
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Rumour has it that a Passive Element (PE) even ended up in one of
Adolf Hitler's desks [1].
US forces had secured the desk from the Reichs Chancellery 1 in Berlin
at the end of WWII, and had brought it to the Allied
Headquarters in Heidelberg [9] as a trophy — one of the spoils of war.
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In Heidelberg, the desk was used by subsequent American commanders, starting
directly after the war with General Patton. Knowing that the British Forces
were being spied on by the US – despite being allies –
the British decided to do the same, and place the US commander under
surveillance.
One night, when the desk was at the workshop of the 21st Support Command
in Mannheim-Seckenheim to be repolished, an MI6 operative was able to get
access to the workshop. There he drilled a hole in the rightmost vertical
timber, just below the top, and covertly installed a PE.
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It is currently unknown what happened to the desk and whether the bug is
still inside it today.
In 2006, a desk that alledgedly came from Hitler's appartment in München
was auctioned in the US. It was said to have been purchased by a private
collector from a government auction in the early 1970s [10].
As it was sold before the PE was installed, this desk in an
unlikely candidate.
Another Hitler desk was rediscovered in Germany in 2014 [11]. It
reportedly came from Hitler's bunker in Berlin 1 and was held for many years
by the US military. In 1996 it was handed over to the German authorities
and placed in a government storeroom in 2000, where it was rediscovered in
2014. It is quite possible, if not likely, that the latter is the actual
desk in which the bug was hidden by MI6 in the mid-1980s.
It is unclear however, whether the bug is still present...
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The accounts differ. Some sources say that the desk was taken from
Htiler's Bunker in Berlin, whilst others claim that it came from
the 'Eagle's Nest' in Bechtesgaden [12]. Our eye witness recalled that it
was probably recovered from the Reichs Chancellery in Berlin [1].
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Below is the circuit diagram of the VR-2/B receiver taken down from the device
in the Crypto Museum collection. It is built around one OC44 and five 2N346
transistors, all of which are Germanium PNP types. At the far left is the detector
diode (D1), which is mounted inside a wave guide with an
optimum frequency around 3.4 GHz.
Q1 to Q5 are all 2N346 Ge PNP transistors with a hFE of 20.
The last transistor (Q6) is an OC44 Ge PNP transistor with a hFE
of 100. It is used here as an Automatic Volume Control (AVC) by feeding back
a portion of the counterphase of the output signal to the base of Q5.
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The interior of the VR-2 can be accessed by
removing the feed horn from the
front, and the knobs from the rear panel, after which the wave guide can be
separated from the brass enclosure
by means of a screw driver.
This may take some effort as the interior is firmly held in place by the
friction between the silicone gasket around the entry port of the wave guide,
and the enclosure.
The image above shows the interior of the device once it's extracted from the
enclosure. A 6-transistor electronic circuit
— the actual receiver — is
mounted to one side of the wave guide. The input from the
detector diode is
at the right, whilst the output transformer is visible at the left. The
detector diode is held in place by a knurled cap at the right.
At the other side, the wave guide has a longitudinal
slot into which a thin carbon card can be inserted by means of a knob at the
rear. This is a so-called card attenuator that allows strong signals
to be suppressed.
The unit is constructed in such a way that the interior can be removed
without disconnecting any wires. The battery compartment is connected to the
circuit by means of a slide contact that mates with the (+) terminal from the
battery. The (-) battery terminal is connected via the enclosure.
When reassembling the unit, an index stub near the entry port of the wave
guide must mate with the index notch in the threaded ring of the enclosure,
to ensure that it is correctly orientated.
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When we received the microwave receiver featured on this page in May 2023,
it was in unknown condition. A first test with an improvised battery
produced noise in the connected headphones, which was hopeful. After opening
the unit, the next test consisted of measuring the voltage over the detector
diode, which was as expected, and taking down the circuit diagram from the PCB.
Once that was done, the voltages at all terminals of the transistors were checked,
to see if they were within expected ranges. As this appeared to be the case,
the unit was assumed to be fully functional. In order to test the detector
however, it was necessary to determine the average operating frequency.
This was done by first finding the cut-off frequency of the SHF part.
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The SHF part of the receiver consists of a feed horn, a wave guide with
a dielectric taper and a detector diode. The cut-off frequency of this
device is largely determined by the longest inside length of the waveguide,
denoted as 'a' in the diagram above.
For the fundamental mode, the cut-off frequency
is calculated with the formula below. In this case, the value of 'a' is
38.75 mm, whilst 'c' is the velocity of light (~ 3 x 108) and
εr — the permittivity of air — is approx. 1.
In reality, the cut-off frequency is lower due to the effects of the
dielectric taper,
but the precise effect is currently unknown. To determine
the optimum frequency, an antenna was connected to a signal generator
and placed in front of the generator's feed horn. The frequency
was then gradually lowered until a maximum strength signal was detected in
the receiver. This appeared to be around 3.4 GHz, depending on the
axial position of the dielectric taper (i.e. the plunger).
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In 1952, this bug was found at the residence of the American Ambassador
in Moscow (Russia), hidden inside a wooden carving of the Great Seal
of the United States. The wooden carving had been presented by the Russians
as a gift in 1945, as a token of friendship after WWII.
It was the first application of a resonant cavity microphone as a covert
listening device, and is also known as 'the Thing'.
➤ More information
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One of the first people to investigate the Russian resonant cavity
— The Thing, or a copy of it — on behalf of the British intelligence
service MI5,
was British engineer Peter Wright.
It took him 10 weeks to discover the operating principle.
In the following year (1953), he developed a similar system for MI5
under the name SATYR. It used modified British umbrellas as
the transmit and receive antennas.
➤ More information
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As part of the EASYCHAIR research, the
Dutch Radar Laboratory (NRP)
also tried to develop a fully passive resonant cavity microphone.
Initially they didn't succeed, but between 1964 and 1965 they managed to
produce a reliably working device, that was illuminated by a pulse transmitter.
The image on the right shows two variants of the device — for 1100 and
360 MHz respectively — that are presented in the original CIA report.
➤ More information
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Device Microwave AM receiver Purpose Reception of passive microphone Manufacturer NERA ASA, Bergen Country Norway Users NATO, MI6 Year 1963 (est.) Operational 1963-1990 (est.) NSN 5865-25-101-1890 Frequency 3.4 GHz Transistors 6 (5 × 2N346, 1 × OC44) Supply 4.5V DC (flat pack battery) Dimensions 490 × 200 × 156 mm Weight 2235 g
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The device is known under the following names:
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- VR2 B
- Detecting set, radar
- NSN 5865-25-101-1890
- NIIN 251011890
- NE3BVR2
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The following people have contributed to this page:
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- Simon Hemour
- Paul Reuvers
- Marc Simons
- Peter Wright [1]
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- Peter Wright (ex-MI6), 1 NERA VR-2/B microwave receiver — THANKS !
Personal correspondence.
Crypto Museum, May 2023.
- Peter Wright (ex-MI5), Spycatcher
1987-1988. ISBN 0-440-29504-1. pp. 24-xx.
- David Wise, Molehunt
10 March 1992. ISBN 978-0394585147.
- Paul Reuvers & Marc Simons, The Thing (The Great Seal Bug)
Crypto Museum, 18 September 2015 (updated 14 May 2023).
- Paul Reuvers & Marc Simons, EASYCHAIR (covert listening devices)
Crypto Museum, 12 January 2016.
- J. Edgar Hoover to John W. Ford
Drawing and Photographs, Russian Resonant Cavity Microphone
FBI. 1 December 1952. Released to a
selected group on 4 December 1952.
Declassified and approved for release by the FBI on 24 April 2019
persuant to E.O. 13526.
- Wikipedia, NATO Stock Number
Visited 12 May 2023.
- Wikipedia, KUKA
Visited 14 May 2023.
➤ German version
- Wikipedia, Headquarters Allied Force Command Heidelberg
Visited 15 May 2023.
- Hitler desk could sell for half a million
Evening Standard, 4 September 2006.
- Found, Hitler's old office desk:
But piece of 1937 furniture will never be sold, say German officials
Mail Online, 1 June 2014.
- Hitler haul is give back
Sunday Mail, 4 January 1998.
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Not to be confused with the ex-MI5 officer Peter Wright, who was the
author of the book Spy Catcher [2] and the developer of the
SATYR covert listening device. The two are not related.
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© Crypto Museum. Created: Tuesday 28 March 2023. Last changed: Tuesday, 02 January 2024 - 14:14 CET.
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![Hitler's desk from his Berlin bunker, found a a storeroom of the German Government in 2014. Copyright AP. [10]](img/ah_desk.jpg)
