On Sun, 14 Nov 2010 19:49:28 -0600, Swingman wrote:

On 11/14/2010 7:23 PM, Leon wrote:
"marc wrote in message
...
Hey All,
I wonder if anyone out there notices this phenomenon when charging the
batteries on your cordless drills or other tools. I have three brands
of cordless drills. My oldest is a Dewalt 12 volt, followed by a
Bosch 14.4 and the most recent is a Festool 12 volt. When I am
charging the Festool we get some interference (buzzing/humming noise)
in any radio we play in the house, both AM and FM. The Bosch and
Dewalt do not cause this interference. Does anybody notice this?
Thanks in advance for your responses.

Marc


I have heard this can happen in older wired homes.... If your wall outlet
has equal sized holes that will permit you to plug in the appliance in
either dirrection, up or down, try unpluging the charger, rotate the plug
180 degrees, and replug.

On word ... "Ground Loop".

A perplexing problem that can have you chasing your tail. As Leon
suggests, switching the plug polarity can solve it, but often it does not.

On a wall charger with a three pronged plug, "lifting" the ground with a
two prong adapter might do the trick.

WARNING: The latter can be a shock hazard with case grounded
tools/devices, but I wouldn't worry too much about that with a battery
charger.

If neither of the above work, then you need to take a look at the
proximity of things like fluorescent fixtures, close by RF inducing
sources, the device, and its connecting wires, acting as an antenna, etc.

As a former recording studio maven and owner, I can tell you that
isolating the source of a hum on an electrical circuit can be as much an
art as it is a science.

No more than a battery charger is used, if the first two suggestions
don't work, I'd be tempted to live with it.

Good luck.
A good isolation transformer (like a OneAC) will usually solve the
problem if it is a ground loop - and often even if it is EMI coming
back the power lines. For the latter, a ferrite on the power cord
often helps too (on the AC cord of the isolation transformer)