"micky"

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.


** You will need to get a portable FM radio and walk about with it to find
where the source is.

Anecdotes:

1. Once had spike noise interference visible on the scope on my workbench -
it began in the early evening and was at a very steady rate of once in 6
seconds. On a portable AM radio, the clicking noise was very clear. I
tracked it down to a small, flashing, red neon sign in the window of a
pharmacy 60 metres away.

2. Had interference on TV at about the same time, visible only on VHF
channel 2 ( 63 to 70 MHz) - the colour would drop out regularly ( every 5 -
10 seconds ) and noise bands appeared. The problem was only there during the
day on work days.

Turned out to be a RF plastic welding machine on 27.12 MHz in a factory 200
metres away. The particular TV was known to be vulnerable to CB radio when
tuned to channel 2.

3. High frequency RF suddenly appeared on my scope one day while doing
testing at full sensitivity ( 5mV /div). It disappeared after 15 minutes but
then returned the next day. Turing up the time base speed showed it to be a
steady signal on 29 to 30MHz.

Switched on my radio scanner and soon found that my upstairs neighbours had
bought themselves a cordless telephone transmitting both ends on the
conversation on 30.15 MHz.


.... Phil