Jeff Dieterle wrote:
I posted a few months back about this problem and have narrowed down the
root cause. The symptom are an overpowering hum at the low end of the am
band. It's being caused by a 3-phase distribution line. I can follow this
line in any direction for several miles any time of day with any of my
vehicles and get the interference. I contacted the power company and
supposedly they're going to look for the cause. Has anybody else dealt with
this type of problem?



Jeff,

This sounds like simple overload of the receiver by 60 Hz fields rather
than any sort of "interference", BPL or otherwise. I have certainly
observed this hum at times, and I suspect most people have.

For the most part power companies in the US are permitted to use 60 Hz
rather freely. There may be no chance for recourse.

It is possible that the 3 phases are not well balanced along this
stretch of line. One phase could be overloaded or close to overload.
That could lead to stronger 60 Hz fields. Power companies usually try to
maintain some degree of balance between phases, along with power factor
correction, but there are probably exceptions.

73,
Gene
W4SZ