Jim K1IR wrote: (snipped)
. And, there was the noise. But, this time I wasn't
> going to start looking for external noises so quickly. Was there still a
> possible noise source in the shack or the house? I realized that I hadn't
> really powered down everything - the receiver was running off the UPS
hidden
> under the desk! I moved the receiver to straight ac power - and the noise
was
> GONE!
>
> The UPS was installed last summer as a protective measure against
lightning and
> other power failures [we have them frequently in my town]. I had just
finished
> telling the world how great the UPS was during the power glitch we
suffered on
> Sunday morning in the ARRL SSB contest, so the device was fresh on my
mind.
>
> The buzzing/hash noise generated by the UPS only appeared when a device
was
> plugged into it. It could be anything. And it would go away sometimes when
the
> device power was turned on - loading the UPS output. This had the feel of
a
> radiated noise from the device power cord. There were a number of
potential
> tests to perform, but the solutions were limited. So, I went straight to
the
> solutions, instead of messing around with testing. I took an old line cord
and
> wrapped most of it around multiple ferrites. I connected the stripped end
to a
> series line filter, and then fed that into a highly filtered
multiple-outlet
> strip with surge suppression. Plugged that into the output of the UPS and
> started testing for noise. Gradually, I added all the loads back to the
> filtered UPS output, and determined that these measures have completely
> eliminated the noise.
I have an APC UPS and have noticed nothing coming from it. I did have a
problem with a UPS sytems a number of years ago. There is a company on the
main street a few blocks from my house that has (still have) a big mainframe
with a UPS system as they need 100% up time as they process banking
transactions such as stockholder accounting and now home banking. I got
the Georgia Power Ex RFI investigator to come out and after looking
everywhere we drove into the business complex. Approaching the computer
center building the noise nearly blocked the local radio stations. The
company's building manager was hostile to anything so I got the IBM FE who
is a ham to approach them. Turns out the employees could only use FM in the
complex and even TV (both commercial and closed circuit) was affected. The
UPS firm came out and quickly found the problem.
Sometimes cleaning up a problem takes a lot of work. I nearly missed a
Mount Athos Dxpedition because of the noise which was S9+10DB with the beam
pointed NE toward both Greece and the firm.
73 Dave K4JRB
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