hum from nearby high-tension wires?

I agree with Aball. If you have a metallic main incoming water line that should be your main earth grounding electrode. Call an electrical contractor and have him check all the earth ground connections, both ends.

Be careful messing with the earth ground connections. Sometimes a difference of potential, voltage, can exist between the ground wire/s, (grounding electrode conductor/s), and the earth ground/s, (grounding electrode/s).
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01-31-06: Steverw
>>"Jea48: maybe 80 feet high. Insulator about the height of a large owl or hawk (maybe a foot?) (I often see them sitting on the line)."<<
>>>>>>>>

Sure sounds like 69KV. No Kite flying near those lines.
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plastic water pipe. Sigh.

Turned out to be a loose connection.

There was no radio noise, even right under the wires.

But now I know a lot more about grounding, thanks for the advice.

Two things about so-called 'harmful' EMF - 1) The fields decrease at a square of the distance, i.e. if you double the distance away from the line, the field intensity goes down by 1/4, triple the distance 1/9, etc. So while there is detectable electromagnetic radiation below the lines, its pretty weak at ground level. 2) If EMF from power lines causes cancer,etc., why isn't there any epidemic among power company Lineman (there isn't). And no, I don't work for an electric utility. But there is No solid proof of EMF from power lines being harmful (unless, of course, you come in contact with one and are grounded)...

Steverw, have you called someone out yet to check your grounding?

What part of the country do you live?

With a plastic main incoming water line you should have a minimum of two 8ft ground rods. One wire coming from your main electrical panel to one of the grd rods and continuing to the next.
Minimum of 6ft apart, 8 to 10ft apart is better. Three or more ground rods is better.

If you have not called someone to come out yet, when you do have the electrician verify just how many grd rods you have. Unearthing the tops of the rods, cleaning and reterminating them as needed.

Depending on what part of the country you live, soil conditions is very important for the type of earth grounding electrode system you have. And depending how old your home is the electrician will be able to advise you what is now required by local codes for your area.

Also while the electrician is there have him check and tighten all termination in the main electrical panel.
Jim