Diathermy was mentioned in the longwire exposure thread and made me think of
this long standing problem here in northern IL..

For some years now, there has been interference on the local 2M repeater
(145.41) which sounds just like the diathermy I used to hear on 10M long
ago. I could tell that it was a crude 60/120Hz. modulated signal which
swept through the repeater input frequency.
It is easily readable on the input over an area at least 3x3 miles. No one
has had the time to spend and I (with some pretty good equip) only went out
a few times (can't spend a lot of time on the way to work... & when I'm
off, it isn't very active), but have limited time as well.

.. It is more active in the morning rush hour and rarely later in the day
and probably never on weekends.


It has to be some kind of RF heating machine, right? Plastic sealing?


Here is a full symptom account to show that I know what characteristics it
has.
I took a spec analyzer out and could see the signal sweeping down at least
five MHz. (where I had it set at the time). I can hear it sweep through
sometimes slowly and sometimes quickly. It so happens that it conveniently
slows down and comes to a stop right around the repeater input - sometimes
ON the input, but spends no more than 2-3 seconds if it happens to stop
there AND stay on long enough. It has a variable time "on"and doesn't
always make it to the input freq.
Now that the repeater is using CTSS full time (last Sept or Oct another
fulltime input spur appeared!) , it doesn't bring up the repeater. However,
you can hear it as it comes into the input across the freq -- if it is
strong enough it will eventually capture and the station talking will go
away, PL detect dies, the beep goes, then this reverses as it continues
through the input freq.

--
Steve N, K,9;d, c. i My email has no u's.