Hello Brian,
I had a similar problem and went through the same procedures you are going
through. Since the source of the problem in not in your house, it is
external. I took a very small portable, tuned it to an AM frequency where
there is no station transmitting, and started walking the neighborhood
listening for noise. I found a tremendous buzzing noise about a half mile
from my house and it was coming from a cluster of 3 power poles. I could
not identify which pole it was exactly because they were within a street
width of one another. I sent a letter to our local power company, drew them
a map of where the noise was coming from, and told them about the problem.
They responded in about one week, checked the area of the poles and
replaced a lightning arrestor on one of the poles. The noise source in my
house dropped from S9 plus to about S3, a dramatic improvement!

If you locate, as close as you can, the source of the problem, chances are
very good the power company will take care of it. Best of luck.

Al KA5JGV
San Antonio, Tx.

Thanks Al. I was hoping I wouldn't have to hunt down power poles again. I'm
not sure if I'd get much response from the local utility company anyway. I
called this morning about all of the limbs and vines hanging over the lines
out here and they said that it was my problem. I'm not sure if that is the
case, but I will look into it. Anyway, I found that listening in sideband
makes it a little more bearable and without the sudden deafening buzz in my
ears every few kilohertz. I don't plan on being here much beyond a couple of
years and I will go out of my way to find a place out in the country my next
move.

-Brian