I was disheartened last week to find a "buzzing" noise in my otherwise
perfect Orion starting in the 10m SSB frequencies and continuing all the
way up the band. Both RX's, happens with antennas connected or
disconnected or even deselected. This weekend I started pulling cables
to eliminate possible problem areas. Imagine my surprise as I pulled the
RCA plug out of the +13.8 V jack in the back and the buzz stopped! What
was it? It appears to be a cheap "Y" cable that I used to power both the
#310 cooling fan and the light in the 238B tuner. If I plug just the fan
without the "Y", no noise. Same for the tuner. If I plug just the fan
through the Y cable, the noise returns, and is originating in the fan
(noise follows the fan spin-up when power is applied, and stops
immediately when the power is removed.) I plan to build my own cable and
will probably add some bypassing there that is effective at 28 MHz. Most
likely no one else will see this problem, but I wanted to post this on
the off-chance that they do.
73, Duane
Duane Calvin, AC5AA
Austin, Texas
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