On Sun, 22 Aug 2004 02:58:27 -0500, Ron Hardin wrote
(in article ):

The usual hum source is nonbypassed diodes in the wall wart, which
provide a nice RF ground when they conduct and none when they don't,
thus changing the antenna system 120 times a second when there's an
instant that they're all not conducting at once.

Even if you ground the radio yourself, they still change the antenna
system, though usually it matters less the more grounded the radio is.

One test is whether the hum changes if you hold a hand on the radio,
improving its RF ground a bit.

The fix is a wall wart with bypassed diodes,

I've got six or seven wallwarts from TadioShack and have never had a
problem.

or NiMH batteries, which
are good enough these days so you don't really need the wall wart.
Just swap a battery set when needed.


Absolutely, we use NiMH on my wife's radios which are liable to be
anywhere in the entire household.

Except: I just don't like doing that with AA's cuz they're so small (in
"playtime") that I don't like jerking them in and out so often.

So I use a "C" cell "battery holder" from RShack and one of their $3
cords and plug the thing into external DC power.

Ron's probably already figured out why I specify "C" cells rather than
"D" but in case anyone is wondering, 2 or 3 sets of rechargeable "D"
cells cost a buncha $$$. If ya got no problems with spending $$$, find
out who is a good electrician in your area and get him/her to run you a
dedicated and filtered/shielded outlet(s) for your radio gear (and
another for your computer gear as long as you're going to the bother
[grin]).


++ Gray //