Topband: Wideband interference

[Tom W8JI]

> I've had many helpful private emails from folks who've seen/listened to
> what I posted.  An RFI occurrence may or may not have a characteristic
> fingerprint, but you're not going to know unless you ask around or search
> the Web for a similar recording.  If someone posted a recording of
> interference similar to what I've personally identified in the past, I
> could certainly respond with my past findings and potentially help them.

That's correct. Some signatures are easily identifiable as a source type. 
Some are not. If I were to guess, probably well over half are identifiable 
by characteristics as a likely source type. That still leaves many that are 
not.

You have to put yourself in an open frame of mind and consider everything.

Electric fences are easy as a group and type. Power lines are easy as a 
group and general type. Fish tanks or other things with thermostats are easy 
as a group containing thermostats. Switching power supplies are easy as a 
broad group.

Your noise appears to be on where people might be up and around, rather than 
on like clockwork as a certain outdoor light level. I'd rule an outdoor 
light out right away based on the times and the changing tone. It does not 
appear to be laundry or cooking related, based on time, duration, and 
changing sound. It does not appear to be home indoor light related because 
it is not steady sound when on. It doesn't cycle off and on with a period 
like a thermostat, so that rules out many things. It doesn't sound like a 
battery charger.

The noise I listened to did NOT appear to be periodic in change, but a 
randomly changing frequency pitch for variable periods.
This potentially indicates a load changing on something randomly over short 
periods, something used when people are likely to be up, but off when they 
are gone or doing something else. TV sets and video systems change supply 
loads like that, and fit the pattern. It might be something else, but lots 
of things can be ruled out based on the sound.

For me, it does help to have some idea what it might NOT be. That way I can 
drive past things I know it absolutely cannot be. Whatever it is, as Jim 
suggested, you will eventually have to DF it and then walk or drive that 
direction and find it. That is what ultimately matters.

73, Tom