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Mason A-3CS
Integrated surveillance receiver - wanted item

The A-3CS is a fully self-contained surveillance receiver, developed and produced in the early 1970s by Mason Engineering Inc. in Fairfield (Connecticut, US). It was the successor to the A-2CS and was effectively a combination of the standard Mason A-2 and the Mason A-3, enclosed in an aluminium container, with all plug-in units and accessories integrated and permanently wired.

The A-3CS is similar to its predecessor, the A-2CS, but contains some improvements. First of all the scales on the individual tuning units had returned from the original design of the A-2.

To the right of the antenna socket at the top left, an extra socket was mounted, allowing multiple external (active) antennas to be connected simultaneously. Furthermore, a portable MPR-1 unit could be connected to some A3C-S units. By using the MPR-1 as the primary receiver, it was possible to process subcarrier signals. The A3C-S was then used as the second demodulator.
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The A-3CS consists of a aluminium container with a removable hinged lid. Inside the lid is a black metal plate that can be used as a base mount for several indoor antennas. All controls and connections of the A-3CS are at the front panel. The unit is fully self-contained and can be powered by the AC mains as well as by an internal battery or an external 12V DC power supply. All power connections are at the far left of the front panel, behind the metal grip.

The bottom half of the front panel is taken by the 11 tuners. A rotary switch at the bottom row, between tuner 3 and 4, is used to select the appropriate range. The top half of the front panel holds the various indicators. At the top left is a digital frequency counter with a 5-digit red display. To its right are two S-meters: one for the HF signal and one for the LF (audio) signal. Below the S-meters are two green fosfor CRT screens: one for the RF spectrum and one for analysis of the LF signal.

The antenna input is just below the frequency counter at the top left. To its right is an expansion connector. It allows multiple (active) antennas to be connected simultaneously. On some A-3CS models, a selector switch is present between the antenna input and the expansion connector. It allows a portable MPR-1 receiver or the later MPR-5 to be used as the input.

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Help required
We are currently awaiting additional background information about the Mason A-3CS. It will be posted on this page as and when it becomes available. In the meantime, if you have any information about this receiver and/or its use, please do not hesitage to contact us. Also, if you have worked with this receiver, we would like to hear from you. Any information you supply to us, will be fully referenced to yourself, unless you wish to remain anonymous.

At present, we do not have a Mason A-3CS in our collection. If you have a spare one, or if you know where to find one, please let us know.

  1. Anonymouse, A-3CS receiver shown above
    Received April 2013. Crypto Museum #500418.

  2. Anonymous, Mason A-3CS with German front panel
    Received March 2009.
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Crypto Museum. Created: Saturday 27 February 2010. Last changed: Friday, 08 September 2017 - 21:23 CET.
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