I wrote earlier in the week about a disturbing amount of power line noise. It had sprung up sometime in the last couple of weeks and was a deafening S9++ on 160m. Not good at all for the start of the low-band season.
A day later, I had an opportunity to try scope it out. I found the noise was readily apparent on an AM broadcast radio. In my car, I tried to find the noise, but found it diminished greatly when I left the driveway, and returned once I parked my car near the church. This mean that it was very local, it wasn't something propagating along the power lines in the front yard.
Getting a little portable broadcast radio, the noise was quite loud in the shack, but diminished as I walked to the church. This meant the noise was likely coming from the parsonage itself.
Next step was to flip every breaker off in the parsonage as I listened to the radio. Of course, once I flipped the very last breaker, the noise disappeared. Turning all the other breakers back on -- no noise. Then it was a matter of deducing what was being powered from that circuit breaker.
The circuit breaker in question, number 15, was powering a few outlets that supplied power to my internet router and other pieces of equipment on my wife's desk. A bit more unplugging found that the parsonage wiring wasn't the culprit, but something plugged into the wall. A bit more, and the cause was found -- it's a wall wart power brick that powers my AT&T Microcell.
When we got the Microcell back 3 years ago, the coverage underneath the parsonage's metal roof was extremely bad. Since then, it has gotten a little better. Until I can replace the bad power brick, we can live without the Microcell.
And no more noise on 160m. Hurray!