----- Original Message -----
From: "Kevin Rowett" <n6rce@arrl.net>
To: <rfi@contesting.com>
Sent: Thursday, March 18, 2004 12:15 AM
Subject: [RFI] help IDing HF noise/interference type
The noise has the characteristic AC hum when an AM
demodulator is used, and
the motor
boat sound when an SSB dem is used. It clearly shows
up as harmonic
carriers. The carriers
appear to be about 10kHz wide.
I've tracked it as low as 1.8Mhz. The harmonics are
every 200kHz (pretty
precisely). Every
other harmonic is one to two S units stronger. The
signal strength
dimenishes with increasing
frequency. It extends we'll into the 20M band. I'm
sure it's present all
the way to 10M, perhaps
even 6M - it's just the signal level has fallen off
enough shorter than 20M,
that I can't detect
it quite as well.
It does start suddenly, like a switch is
thrown - I've been operating
a contest, and it will appear suddenly.
-------------------------------------------------------
---------
It sounds like a "smart" battery charger, although
the 200Khz spacing is a little wide. The ones I've
encountered are spaced about 70 Khz. These devices
are essentially switching power supplies, and are
murderously noisy.
Look for a kid riding around the neighborhood
on an electric scooter. These scooters are becoming
extremely popular, and are sold in auto parts
stores, such as Pep Boys and AutoZone. The chargers
run at 24 or 48vdc. I put a Radio Shack AC line
filter on the input of one in my neighborhood and it
didn't help at all. Fortunately, the scooter was so
poorly made that it totally failed in a few weeks,
so my problem has gone away.
Recently, I have begun to see "smart" 12V chargers
for cars in the ads.
Dave Hachadorian, K6LL
Yuma, AZ
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|