Colin Lamb wrote:
> I have the Icom 751A with a built in supply. It does just as Tom
> says. People on frequency do not complain about the hum - but the
> white noise off frequency is substantial. This is definitely a rig
> that neighboring hams do not appreciate.
I had a borrowed 751 (not the A model) with the built-in switching
supply for a time. It generated enough noise on receive to interfere
with weak signal reception. I sent it to ICOM, and they fixed a bunch
of stuff, but not the noise. They 'couldn't hear it'. It never
occurred to me that it was the power supply, and I returned it to its owner.
This field day, I had a computer monitor with an external switching
supply. I could reduce the noise with ferrites, but not entirely
eliminate it. We lived with it. We also had a little clip-on lamp with
a 12v halogen bulb, and of course, a switcher to power it. It generated
a tremendous amount of wideband noise, and no amount of ferrites had
significant effect. Luckily I found a 120v incandescent fixture, or we
would have had to operate by the light from the monitor.
Unfiltered, unshielded switchers are everywhere lately. What a pain in
the butt!
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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