Someone in my neighbourhood got a new toy for Christmas, and when they play
with it I get a noise repeating precisely every 200 kHz from about 4 MHz
though to 30 MHz - some places worse than others - i.e. around 8 and 15 MHz
they exceed S9. I have sent audio and spectrum recordings to a specialist in
RFI, who was able to determine that it is a switcing power supply, but just
which one and for what is still unknown.

All wiring in my subdivision, including telephone and cable TV is
underground. Other than satellite TV antennas the only visible antennas or
feedlines within at least half a mile are mine. When spring comes I'll try
to localise it with a portable receiver. It is definitely none of my
immediate, within 200 feet, neighbours. I suspect a plasma TV.

In the meantime I just have to avoid multiples of 200 kHz when whatever it
is is being used.

Dave

"Edmund H. Ramm" wrote in message
...
In "DougSlug"
writes:

I understand about the noise and harmonics a switcher can generate, but
the thing is that my antenna is mounted outside on a mast 25 feet up.
All the wiring in my neighborhood is underground.

The neighbours' tv aerials are also underground? The neighbours'
inhouse mains wiring is underground?

It's not clear to me how I could be getting such strong interference
in this case.

The rf energy creeps up the coax' braid and along the mains wiring and
is radiated from there.

My neighbour once had a switch mode psu which pegged my rx' s-meter
on 80m and was still about S5 1km away (spikes 100Hz apart).

QRM from el cheapo switching psus can possibly be cured on a one by
one basis, as hopefully there aren't too many of them. As all and sundry
have at least one tv set at home, QRM from the line output stages has to
be endured or somehow be reduced at the receiving end (notch filter et
al).
If it's any consolation to you, the latter type of QRM will gradually fade
away as more and more flat-screen tv sets enter homes, and will be
replaced
by a much more horrible QRM when said flat-screen is of the plasma
variety.

73, Eddi ._._.
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