"Robin Cassidy VK3AYZ" wrote in
message om...
Are you using a switch mode power supply to run your radio's?

You can get modulation products produced by switching noise on the supply
rail.

Why do switchers have such a reputation in ham radio?

I realize it's possible to hose up a switcher design pretty thoroughly, (you
can also make a 7805 into about a 2W transmitter on 160M if you're not
careful), but I've never seen the sorts of problems that I keep hearing
associated with them..

BTW, I design switchers, and use them for power supplies in low noise
systems, without shielding or other expensive "voodoo" of any kind.

When designed properly, they are very efficient, and very nearly "silent".