Time wise it could be an RF drier for resin.
Lexan for one has to be thoughly dried before molding which would be around
start of the shift. If the top is not fully closed or the electrician has
left the rear panel off then the R.F. would get out. The bottle used has
about 6Kv on it at about .4A so even without an antenna the interference can
be widespread in the area that you mentioned.
Art
"Ed Price" wrote in message
news:jaoXb.72863$fD.59039@fed1read02...

"Steve Nosko" wrote in message
...
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.



Plastic sealing, using dielectric heating, is often done with the ISM at
27.125 MHz. Loading of the machine might (but isn't supposed to) pull the
frequency. The 5th harmonic is a long way from the 2-meter band, and so is
the 6th. If the RF source is quite close to the repeater, maybe you are
seeing an image response to the 5th harmonic.

You don't need to have a heavy-industrial setting; I once tracked some RF
unhappiness in Milwaukee to a neighborhood shop making vinyl auto tops.

Ed
wb6wsn