[Boatanchors] Peristent, annoying, intermittent, elusive QRN problem: help please!

Tue, 12 Mar 2002 19:15:11 -0500

Had that problem myself a few years ago. S9+20 noise from 10khz well
past 10 mhz, then nothing. Intermittent silences but generally round the
clock. First step was to disconnect the antennas - golden silence! Next
step was to take a portable BC/SW receiver and kill the main breaker for
the building. Again, with the power off, silence, so the problem was in
the building.

Next step, with the portable tuned to the noise, turned on the breakers,
one by one. Found one that killed almost all the noise when turned off.
This fed a refrigerator whose wall outlet had been fitted with a
SCR-equipped 'Power Saver', which had decided to live out the rest of
its (soon to be shortened) life as a broadband QRM generator.

Only a small bit of interference remained, and this was traced by the
same method, to a photocopier with some sort of always-alive circuit. An
IsoBar line filter solved that problem without opening the case up.

If your interference is generated in your own building, and you have
access to all of the electrical service, you can solve the problem
easily. Just start by killing the power, be methodical, and think out
your steps carefully.

Arthur Shulman

--------------------------------
John Starr wrote:

> I had a very similar situation some years ago that was very
> similar: persistent intermittent noise on/off like clockwork and
> only at night.  I eventually traced it to a electric warming mat
> with a bad bimetallic thermostat. Here is the story:
>
> My wife likes to get a head-start on her garden by growing
> seedlings in the house.  I rigged up an insulated box in the
> basement that had a fluorescent light and warming mat.  The
> light was on a timer and the warming mat was powered all of the
> time.  The timer was set to mimic daylight, on in the morning,
> off at night.
>
> During the day the fluorescent lamp kept the plant box warm
> enought so that the warming mat stayed off.  At night the light
> would go off, the box would cool down and the heating mat would
> cycle on and off.  Since the basement stayed at a relatively
> constant temperature, the heating mat cycle also stayed
> constant.
>
> I had a devil of a time locating the source of the noise since
> it was being radiated through the house wiring and so appeared
> to be everywhere.
>
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]]On Behalf
> > Of Will White
> > Sent: Tuesday, March 12, 2002 1:18 AM
> > To: BA
> > Subject: [Boatanchors] Peristent, annoying,
> > intermittent, elusive QRN
> > problem: help please!
> >
> >
> > I have a local noise problem I am hoping someone can
> > help me track down.  I hear
> >
> > S-6 or 7 loud, 'coarse' has on all HF bands, on all
> > frequencies, though the
> > intensity of noise diminishes somewhat on higher
> > bands.  On 40M, my main band,
> > it is all but intolerable, making QSOs with all but
> > the loudest stations
> > difficult, even at 12 WPM or so.
> >
> > The noise comes on for exactly 2' 15", and goes off
> > for exactly 1' 25". Over and
> >
> > over. I have timed it many times over two weeks.  The
> > noise is only there after
> > dark. Aha! But I have searched and searched for an
> > intermittent streetlight, to
> > no avail. I have gone about three blocks in all
> > directions from the house in
> > this search, and also looked for automatic
> > driveway/porch lights nearby, but
> > can't find any. What the &*%$ can this be!??  I am
> > really puzzled by the exact
> > timing, since it would seem that a streetlight
> > malfunctioning wouldn't do this,
> > and a driveway light might stay ON for a specific
> > time, but not off! HELP!
> >
> >
> >
> > --
> > Will White, KD7BFX
> > Seattle WA US
> > King County, Grid CN87tq
> > ITU Zone 6, CQ Zone 3
> > ***************************************************
> > "The wireless telegraph is not difficult to understand.
> > The ordinary telegraph is like a very long cat.
> > You pull the tail in New York, and it meows in Los Angeles.
> > The wireless is the same, only without the cat."
> >
> > - Albert Einstein
> > ***************************************************
> >
> >
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> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/boatanchors
>
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