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Mason was an American manufacturer of miniature probe receivers, that
were used to trace bugs (miniature spy transmitters).
The company was founded in the early 1960s by Francis (Frank) G Mason
and all equipment in the early years was developed by himself.
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Mason Engineering Inc. was based in Fairfield, Connecticut (USA),
where all equipment was assembled by some 60 employees.
The company developed a wide range of TSCM equipment
(Technical Surveillance and Counter Measures) and for more than 30
years, they were one of the key suppliers to governments all over
the world. Well-known bug finders were developed, such as the
Mason A2, A3 and the MPR-1 shown here. Later versions, such as the
MPR-5 are still widely used by specialised TSCM companies around
the world.
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In the early 1990's, the tide turned against Mason, when both Frank Mason
himself and the company were prosecuted and convicted for breaking the
FCPA
[1]
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after he supposedly tried to bribe German Government officials when trying
to win a large contract with the West German Military Intelligence
Service (MAD). At the moment, the company does not appear to exist
anymore.
Despite all this, Mason can be considered one of the pioneers of
TSCM equipment and his receivers are beautiful examples of clever
engineering; way ahead of their time.
According to a former Mason employee
[2]
, most of the
design and engineering work was carried out by Frank Mason himself,
and all electronic and mechanical parts were built in-house.
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As far as we know, the A2 was the first mini probe receiver developed
by Frank Mason in the mid-1960s. The brochure that is available for download
below, was issued in 1966, so it is likely that the A2 was introduced in
the same period.
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Optically, the A2 is one of the most interesting receivers of the Mason
family. The unit is stored inside a leather suitcase, together with all
of the accessories and plug-in units (see below).
The main unit consists of a very small receiver with a rather large
oscilloscope display unit bolted on top. The various plug-in units
are attached to the right of the receiver. In the images below,
the receiver is shown with the 70 - 295 kHz module attached to it (yellow).
Each unit is identified with a unique colour as is clearly visible
in the images.
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The display unit, bolted on top of the receiver, is basically a panorama
viewer. The green fosphor screen is on the right of the unit and the valve (tube)
is mounted under an angle, to enable the user to view its display without
turning the unit on its side. Later versions, such as the Mason A3, were
supplied with a small mirrow that allowed the display to be viewed directly.
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Over the years, the A2 (see above) was modified and improved a few times and
different models of the A2 were issued. One such example is the the A2C-S,
a complete self-contained receiver in an aluminium case.
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The A2C-S is functional identical to the A2, but rather than supplying a series
of separate plug-in modules and accessories, all relevant components have been
combined in an all-in-one solution. Instead of using patch cables to select a
different frequency range, a built-in selector switch is used, which is visible
at the bottom centre of the front panel.
Furthermore, the two functions of the green oscilloscope have been
split into two separate displays, allowing both the HF and LF spectrum to be
monitored simultaneously.
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The unit can be powered directly from the mains (115 or 230 Volt) or from its
own battery unit that is hidden inside the top lid of the aluminium case (see
the images below). The telescopic antenna is connected to one of two sockets
in the upper left of the unit, depending on the frequency range that needs to
be monitored. As with all Mason receivers, a wide range of different antennas
should be available, as each frequency band has different requirements.
Please note that the frequency scales are missing from the individual frequency
modules. Instead, the unit is equiped with the digital frequency readout (behind
the antenna).
Apparently, this was not a good idea, as the scales returned on later models,
such as the A3-C.
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In 1968, Mason started the development of the successor to the A2-series,
the Portable Receiver A3, which was introduced in 1971.
Like with the A2, a number of smaller changes and improvements were
issued over the years, finally leading to the A3B shown below.
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The design of the A3 is similar to the A2, but a number of significant
improvements are clearly visible. The (vulnerable) antennas are no longer
directly mounted to the tuning units and the oscilloscope is much more
compact and user-friendly. Furthermore, the cableing is much better
organised.
The oscilloscope is mounted vertically inside the lid of the case,
with the display facing upwards.
It is held in place by four velcro dots.
A small hinged mirror is present at the top, to allow the display
to be read easily by the user (see image).
The separate tuning sections are no longer supplied as separate plug-in
units, but are mounted together in a single case. Short patch cables are
used to connect a tuning unit to the receiver. The receiver itself is
housed in a separate metal case, seated behind the tuning units.
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All units are packed together in a nice compact leather case, allowing
the A3 to be carried around without attracting attention.
A separate MWT-1 10 GHz module was available as an option.
When present, it would be mounted with four velcro dots in the bottom
right of the lid of the leather case.
This option is not present in the A3B shown here, but the outlines are
clearly visible as cut-outs in the green foam.
The additional unit covered all frequencies between 2 and 10 GHz
in two ranges (2-5 GHz and 5-10 GHz).
The A3B was very popular with the US intelligence agencies and also with
the agencies of various European countries. The unit shown here has been
used for many years by the United States Information Agency (USIA).
A similar unit, with the optional 10 GHz extension present, was
revealed
as a public exhibit by the US Department of State,
Bureau of Diplomatic Security's,
Countermeasures Directorate in 2008 (see the rightmost image below).
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Mini Probe Receiver MPR-1
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The MPR-1 was developed around 1980. It's a small modular design
that can be enhanced at will. The basic unit consists of the Mini
Probe Receiver itself (MPR) and a tiny green oscilloscope.
A small metal frame was used to hold the two units together.
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The MPR-1 could be used for a very wide frequency range and separate
plug-in modules were available for each different frequency band.
In second image below, the MPR-1 is shown with a plug-in module that
covers 800-1600 MHz.
In all, 12 different plug-in frequency modules were available,
spanning a very wide frequency range from 20 kHz
to 10 GHz (!)
The main unit was packed in a sturdy unobtrusive case, together with
the frequency modules and various accessories, such as a power supply,
cables, antennas, headphones and user manual.
The unit in the image on the left, is packed inside a Samsonite
attaché case that was commonly used in those days.
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The MPR-1 is a very sensitive receiver, capable of finding very small
and weak bugs, but the wide frequency span of each module also has its price.
When 'sweeping' a room, one has to be careful when using multiple MPR
units with the same frequency plug-in, as the radiation of the receiver's
local oscillator is strong enough to 'confuse' your collegues.
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Mini Probe Receiver MPR-5
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The last member of the Mason family was the MPR-5, developed in the 1990s.
Cosmetically, it closely resembles its predecessor the MPR-1 (see above).
The small receiver has similar looks and the outer dimensions are identical.
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But there are some important differences.
First of all, the controls of both the receiver and the display unit are
slightly different. New on this model is the addition of a narrow frequency
counter with LCD readout, mounted in between receiver and display unit.
The most striking difference however, is that the adjustment controls have
been moved to the receiver unit, whereas on earlier units (MPR-1) each
plug-in unit had its own controls. The new design is more cost-effective
and has a far more accurate adjustment.
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Despite the fact that Mason went into liquidation in the late 1990s,
the MPR-5 still is considered one of the most modern and useful mini
probe receivers of the analog era. It is still widely used today by TSCM
companies all over the world.
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