[Premium-Rx] Re: DSI 1250 RX

[Jerry T. Dowell]

The DSI receiver was probably the best TEMPEST test receiver, certainly up until 1991, when I left the TEMPEST test game. It was superior for that purpose to the WJ-8940B, its replacement whose number I forget, and the AEL ATTR. (The later was used extensively by the government and was the RX one had to use in the day-long hands-on test for TEMPEST ENGINEER certification by NSA.) The ATTR was easier to use for manual work than the DSI, however. The DSI, in the DSI-9000 system, was the first RX certified by NSA for automated testing. The RX was controlled by an HP workstation with sophisticated, classified software, first under the HP Basic operating system and later under the HP Pascal operating system.

The DSI was terribly unreliable. We had to have factory service certainly at least monthly, on occasion weekly. Nevertheless, it was quite a receiver. Not for general listening, however. Sensitivity was certainly poor by premium-RX standards (better than the ATTR, however) and skirt selectivity leaves a lot to be desired (a consequence of TEMPEST testing requirements for filter performance).

Jerry
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