>was picking up the 2 meter RF and modulating it with whatever, creating wide
>CRAP that >spread over a considerable chunk of spectrum.
In some cases that's known as tunable hum. Probably not here, but
what happens may be similar:
diodes rectify the 120 v. line directly with no 60 cycle transformer
isolating them from the line. Therefore, they switch the sine wave
from the power outlet directly, and basically that DC is filtered and
then chopped at high frequency to a nice light weight toroid for the
voltage step down. That's a super simple overview of a switch mode
supply so please don't hijack the thread with picky corrections.
When a strong RF signal appears on the AC line to the power supply,
the diodes switch it too, and that RF gets re-radiated but with a 120
cycle hum modulating it that comes from the switching diodes. When
you drive under a pole pig drop with your car radio tuned to a nearby
strong AM broadcast station and briefly hear hum in the audio, you are
hearing the result of a computer power supply or some other cheap
supply modulating the RF. Tune away to an open frequency and the hum
and signal vanish. The fix is to bypass the diodes with capacitors
but that would cost the manufacturer a few cents per unit and who
listens to radio nowadays anyway? Just a bunch of old folks. Who
cares about them.
73
Rob
K5UJ
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