[Amps] Switching Power Supplies

[Vic K2VCO]

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