Thanks to everyone who replied. On a related note, I found something at home that probably answered my question. Lately I noticed that there was a weak carrier centered on 144.390. This was causing my APRS IGate to not transmit because it sensed that the channel was busy. It took a long time to find the source which turned out to be my APRS IGate computer. Further investigation showed that it only happened when certain combinations of programs were running. Any other combination of running programs created no interferenc anywhere in the 2m band. Further investigation with a spectrum analyzer confirmed this. I then tried using my frequency counter to get an exact frequency only to find that it generated another half dozen spikes throughout the 2m band.
So I think the answer is that just about anything electronic is a potential source of my interference and sometimes the source is so bizarre that you would never suspect it. 73, Bruce
