[Yaesu] 990 'feedback' w/12 V supply

[Brian Smithson]

I've always been running my 990 off the AC line until a few weeks ago when I
hooked it up to my 40A power supply to see if that would help with some
computer interference I was experiencing. It didn't, but I left it on the PS
for grins. All has been well until this weekend.

Sunday, I was casually operating sweepstakes and I noticed that I could hear
my own voice distored through the headphones when I transmitted. At first I
suspected my 15m dipole, but it happened on all bands on all my antennas.

I went backwards in time disconnecting accessories I'd connected, one at a 
time. The problem didn't go away until I disconnected my power supply and went
back to using the AC! Reconnecting all the accessories (keyer, external sp.,
CAT interface) leaving the power from AC still got rid of the feedback.

Question: Why would a 12V connection cause the 990 to do this? I have three
other things connected to the power supply: A NIR-12 DSP unit, a KPC-3 (off),
A Yaesu FT2200 (also off).

Any ideas?

Tnx es 73!
n8wrl
-Brian


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