amdx wrote:
I have an undercounter AM, FM radio. When I plug the power supply to my
laptop
into an outlet in the same room, the FM signal gets very noisy. Upon further
investigation, I found that just plugging the ac cord into an outlet and
holding it near the laptop causes the noise. Also holding the laptop near
the power cord of the radio causes the noise. Holding the laptop near the
radio doesn't cause the noise.
So I think the laptop is generating noise that gets induced into the ac
line.
I tried wrapping the radio cord about (ten turns) through a (junkbox)
toroid without any help to the problem. The toroid is 3" in dia. It's
probably an iron laminate core
(low frequency) so may not be right for filtering the ac line.
My next step is to go to Radio Shack and try to purchase some clamshell
type
line filters.
Any ideas to eliminate this noise from the ac line?
Mike


Some of these undercounter AM/FM sets use the power line as an
"antenna". If you look closely you might find an antenna screw with a
metal clamp going around the power cord. If this is the case, you are
likely creating an extension of that antenna by plugging in one end of
the computer power cord and placing it near the laptop (which is
undeniably an noise source).

The fix is to get a separate FM antenna for the receiver and mount it
outside or at least some distance from your computer. Having a balanced
300 ohm type antenna might solve the problem.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P