I recently found a modest-level signal on various HF bands,
20 to 50 kHz apart. I finally got annoyed with it enough to
start flipping breakers in my house. Finally got to the breaker
for the shack, and low and behold, the noise *changed*
when I hit that breaker -- it didn't go away, but it got less
and sounded somewhat different.
It turned out to be a Tripp-Lite UPS that I just bought
for the shack computer (model OmniSmart 1050 PNP) --
it was generating the noise, and when it lost power, it still
generated noise, but was less and sounded different.
My other UPS (Tripp-Lite BC Pro 850) does not appear
to have this problem.
Moral: just because you turn even the main breaker off,
doesn't mean that everything is really off.
And if anyone has ideas on taming a noisy UPS,
I'm all ears.
--
Dave NØRQ
----- Original Message -----
From: "Scott Ginsburg" <k1oa@comcast.net>
To: <rfi@contesting.com>
Sent: Monday, June 14, 2004 8:50 PM
Subject: [RFI] need ideas on hunting down QRN-like noise source
>
> I'm currently plagued with two sources of HF RFI, and for the
> moment am concentrating on locating one of them. Any help
> I can get from the RFI sleuths on the list would be greatly
> appreciated!
>
> The noise in question showed up about a month ago, and appears
> as a combination of white noise and random, rapid static crashes.
> The static crashes, or bursts, sound a lot like heavy QRN.
>
> It is typically the loudest on 14 MHz, and can be heard from 7-24 MHz
> when it's at its worst, with peaks on 14 MHz of 10 over S9. I hear no
> buzzing when listening on AM. My noise blanker has no effect.
>
> Its presence can't be correlated with weather. I hear it on both wet
> and dry days, wind or no wind.
>
> It seems to peak from a certain direction when I listen on my HF log
> periodic. I've driven the neighborhood streets (up to 2 mi away) with my
> 706 and hamstick in the car and can hear what I think is the noise in
> certain locations, but never loud enough to be a "smoking gun". I
> verified it's not coming from my house, by killing power and listening
> in the driveway on my 706 to the noise.
>
> Early morning is typically very quiet. At 6:30 AM local time I usually
> hear only silence, or a few weak bursts of noise which sound like the
> problem. It typically peaks by noon. I almost always hear it in the
> evening and at night.
>
> Any hints anyone might have as to what a possible source might be or
> the best way to continue trying to track this down would be
> appreciated.
>
> 73,
> Scott, K1OA
>
>
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