Thanks for the good info on the doorbell transformer,Ive changed one out before,but didnt know the other stuff.Thanks for the info on that.
Interference is significantly reduce when raining and before everything dries up. Interference is most likely caused by an arc somewhere...and the moisture provides a conductive path instead of breaking down the air with an arc. This tells me the source is on a pole, not in a residence.
Doorbell transformers have a thermostat in them, to prevent them from overheating. They're often located in an attic where it's hot. The thermostat will flip back & forth, generating RF noise, and propagating it through the powerline to the pole and down the street. If the doorbell button is lit, you can see the flicker simply by looking at the button. Other common culprits are fish tank heaters and electric blankets; that have similar thermostats.
In this case, power was shutoff to the residence and the interference doesn't go away. The probable source was identified with an AM radio at 160MHz. Noise at lower frequencies (like AM broadcast, ~700khz) can propagate several blocks from the source down the powerline.
I am hoping to convince the power company to check two poles for loose/corroded hardware, ungrounded brackets, etc. And trim around the lines.
Thanks for the good info on the doorbell transformer,Ive changed one out before,but didnt know the other stuff.Thanks for the info on that.
Umm no the doorbell xfmr aint necessarily goin bad.
Back when the Co. used to care they had a group of engineer types that had a bunch of test equipment for this you would start out with an AM radio just off a station a bit to get in the area, then they had a bionic ear that was a parabolic microphone like they use at football games to hear the guys swearing from the sidelines. Usually that would find the problem the trick is if you found something fix it while listening to make sure it goes away whether it was a loose nut and bolt or a cracked insulator. They also used an infrared camera you see a leaking insulator especially after it rained.
No progress yet. Power company is getting engineering involved.
older glass ladder type HVLA's will cause interference in wet weather. Cracked pin insulators will also do this but are very hard to find. Another hard one to find is a copy machine heating element. it's more intermittent only when the copier is running.
Id bet the instrument I saw a guy using could get close,but may not find it....To this day I still dont know what it was called,but it picked up a bypass switch arcing that day and he said it cost around 10,000 bucks.Some NASA type of guy
Yes I'm a ham (geez we're easy to spot).
The parabolic dish receivers are high frequency (1 GHz+) AM receivers. They won't work if there are trees or anything else blocking your visual path.
There's also the hot stick sniffer which uses a ~1 MHz AM receiver. Very close to the HV obviously.
Both are expensive, but you can save lots of time and effort. Your other option is find the pole, check everything for corrosion and proper torque. Then start replacing things until it goes away.