Portable intercept receiver
The A3B was a portable intercept receiver, designed by
Mason Engineering Inc. (USA) as the successor to the
Design of the A3 started in 1968, but it was not released until 1971.
Although the A3 was an improved version of the A2, the A2 remained in production
until 1990, and was sold alongside the A3 and later models, such as the
Design of the A3 is similar to the A2,
but with a number of significant improvements.
The rather (vulnerable) antennas are no longer
mounted directly to the tuning units, and the oscilloscope is much more
compact and user-friendly. Furthermore, the cableing is organized better.
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.
The oscilloscope is a separate unit.
All units are packed together in a nice compact leather case, allowing
the A3 to be carried around without attracting attention.
A separate 10 GHz (MWT-1) module was available as an option.
When present, it would be mounted with four velcro dots in the bottom
right corner of the lid of the leather case.
This option is not present with 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
A similar unit, with the optional 10 GHz extension present, was
as a public exhibit by the US Department of State,
Bureau of Diplomatic Security's,
Countermeasures Directorate at an exhibition in 2008
(see the rightmost image below).
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