On 9/13/2011 7:16 AM, kc0hfl@cox.net wrote:
> Current set up Radio Flex 5000 driving the 374A
The problem is almost certainly at the Flex, and I'm guessing that the
difference is the additional power of the larger amp.
Assume a Pin One problem at the Flex, and add multi-turn ferrite chokes
to audio lines (mic, processing) and any other lines that plug into the
radio. Study http://audiosystemsgroup.com/RFI-Ham.pdf
There's another mechanism that SOUNDS like RFI, but is NOT. W8JI
alerted me to it, and I've duplicated it in my station. It happens when
you have a 12V rig with V- bonded to the chassis of a power supply, and
audio accessories that feed the radio powered from that 12V supply.
What happens is that varying DC current with modulation causes
modulation of the V- line by the IR drop, and that modulation is added
to the audio. It SOUNDS just like SSB detected by an AM detector, so you
think it's RF feedback
73, Jim Brown K9YC
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