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Professional radio bug
The Mactron bug was a professional miniature crystal-based transmitter
built in the early 1990s by Mactron in Oosterbeek (Netherlands). The
device was intended for bugging
(eavesdropping on conversations) and for covert operations,
primarily by government agencies such as the police.
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The device measures 51 x 15 x 16 mm and was often housed in a black
box along with a 9V block battery. The circuit consists of a
varicap-based modulator, a crystal oscillator and an amplifier
that delivers a Frequency Modulated signal with an
output power of 150-200mW.
The Mactron bug operates in the 140-170MHz range for which ordinary
scanner crystals were used. The device shown here operates at
approx. 142 MHz.
For eavesdropping on a conversation, a sensitive electret
microphone is needed, which should be connected via an external
amplifier.
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Thanks to the small form factor, the Mactron bug was suitable for a
wide range of applications. It was sometimes used as part of a larger
bug, such as the purpose-built telephone bug shown below.
It could also be used as a homing device, for
example when tracking the vehicle of a criminal in the days when GPS
was not yet available.
The Mark II version of the Mactron bug was sometimes supplied
as a test transmitter with bug tracing equipment like the
Scanlock ECM.
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In the late 1990s, a bug was discovered in the telephone exchange of a
company in The Netherlands. It was a professionally designed, purpose-built
eavesdropping device that was connected to the company's central office line
(CO) and transmitted all of its conversations.
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At the heart
of the telephone bug was a Mactron FM transmitter with a short
helical antenna. It was mounted on a piece of full-copper PCB,
along with the other components of the circuit.
At the top right is a current transformer that allowed the telephone line
to be tapped without drawing any current from it or disturbing its impedance.
Furthermore, the bug transmitted only when the telephone line
was engaged. For these reasons the device remained undetected for a long time,
and allowed many conversations to be recorded before it was finally discovered.
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The company involved, became increasingly suspicious after more and more critial
information about recent developments had leaked to their competitors.
Although the remote line check, that was carried out by the telecom provider,
did not reveal anything,
investigators later discovered the bug when physically checking the lines
and the exchange system.
When studying the image above, it becomes clear that the bug was a one-off
that was built especially for this purpose. It also becomes clear that the
person who built it was a professional who knew what he was doing.
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The initial version of the Mactron bug (shown above) was not
suitable for the direct connection of a microphone. If it was
used for eavesdropping on a conversation in, say, a room, an
extra PCB with a pre-amplifier had to be installed between
the microphone and the transmitter.
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As a result, the Mactron bug was only suitable for applications
where a line-level signal was available, such as the telephone
bug described above, or when audio was not required, for example
when tracing a car or a person.
Especially for bugging rooms with the purpose of recording
human voice, an enhanced version of the bug, known as the
Mactron Mark II was released. It featured a very sensitive
two-stage audio amplifier that allowed virtually any type
of microphone to be connected to its input without any
further components or adjustments.
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The Mactron Mark II was slightly longer than the initial version,
but was still small enough to be built inside many different
concealments. As these types of bugs are driven by a quartz crystal,
they are extremely stable. Furthermore, the RF output of these
bugs is remarkably clean.
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For simple eavesdropping tasks, the Mactron Mark II was also available
in a black plastic case, with space for a standard 9V battery and
a wire antenna. This version was also used for training puposes,
such as sweep teams that had to be trained on a
Scanlock
or a Delta-V bug tracer.
The image on the right shows a complete Mactron Mark II bug.
As the unit does not have a built-in microphone, an external one,
such as the plug-on electret microphone shown here, is always needed.
Alternatively, a
wired body microphone (e.g. phonak) could
be used instead.
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A small external microphone was often used for covert operations
and on infiltration tasks. The transmitter was then hidden on the
body, safely protected by the operator's clothing, whilst the
microphone was installed in a position where it could pick up the
sound of the conversation.
The interior of the cased version of the
Mactron Mark II is very straightforward; it just
contains the
Mark II PCB, the 9V battery
a switch and a connector for the microphone. To make the circuit
more stable and robust, and to protect it from prying eyes, it was
covered in hard brown epoxy.
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Although in most cases eavesdropping involves recording or transmitting
a (voice) conversation in a room or in a car, this is not always the case.
One example is when you want to follow (track) a person or a car, or when
you want to retrieve (trace) a package, such as a money transport.
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Especially for tracking and tracing applications, Mactron released onother
variant of their famous Mactron Bug: the Mactron Beacon.
Like the Mactron Mark II it is slightly longer than the original Mactron
bug. Instead of the microphone amplifier of the Mark II, a
HEF 4010 IC
is used to create a timer with a duty cycle of 25% (1:4).
Every four seconds, the transmitter is turned on for approx. one second
an is then switched of for three seconds. This was done to save power
and allowed the beacon to transmit at full RF power for several days
on a single 9V battery.
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As the Beacon's PCB has the same form factor
as the Mark II PCB, it can be fitted inside the same enclosures and
concealments.
When on the air, the Mactron Beacon transmits a silent carrier, making it
difficult to trace the transmitter based on the strength of it audio signal.
For these types of bugs, the interceptor would normally use a sensitive
Single Side Band (SSB) receiver. By tuning slightly off-channel, the receiver
produces an adjustable tone (beat). The volume of this tone is a measure
for the signal strength of the received signal.
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Mactron was an electronics and security company that was based in
Oosterbeek (Netherlands). The company was established in the late
1980s and specialized in video surveillance equipment for banks,
such as the Dutch ABN-Amro bank. A special department of Mactron
developed and built high-end security products in low quantities,
the so-called specials, such as the Mactron bug featured
on this page and the succesful Necktie Bug
that was used for covert operations.
Around 1990, the company attracted additional capital and moved
to a new building where sufficient space was reserved for the
various activities. New personnel was attracted and various new
products were developed. In 1992 however, the company faced bankrupcy
after an alledged fraud by one of its new directors and bad
strategic decisions. The company was subsequently liquidated,
leaving the original owner empty handed.
Parts of the old Mactron eventually went to a new owner.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Sunday, 19 May 2013 - 00:19 CET
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