Saturday, September 28, 2013

Yes, It's That Time Of The Year...

...when I fire up the good old R-390A again. And it never lets me down. This one was restored to perfection with the invaluable help from Dallas Lankford, to better than specified performance (sensitivity is -115 dBm on AM, 6 kHz bandwidth,400 Hz tone and 30 % modulation). The stock filters were replaced with filters more suitable for MW DX, and the last modification involved an AM Synchronous Detector. Once the set is sufficiently warm, it's rock stable.
R-390A - still glowing

Dallas also helped make a complete inventory of valves, lamps and other parts that could come in handy during the next 50 years or so.

This R-390A is a relatively new one, manufactured in 1967. Its pre-Mjelde history is rather obscure, but there is reason to believe that it was one of the workhorses at a Norwegian Army Sigint facility. They were supposed to be demolished after completing service, but story has it that some operators who were also radio amateurs managed to save some of them. I bought it from a radio amateur in 2004.

The R-390A hasn't been among my most important DX receivers, however in many ways it's still a reference receiver for todays' SDRs. Although it can't compete with the versatility of SDRs, on single frequency monitoring it is still number one.

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