On Apr 29, 5:55�pm, "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

So, is it conducted noise or radiated noise?
The solutions are different.

If conduted, you can stop it with filters.
If radiated, you can stop it with shielding.
If both, you need both solutions.

It "sounds" to me like the radio is the problem, not the laptop, or
the laptop power supply.
Also, it's likely the weaker the FM station, the more noticable this
could be, depending of course on the type of detector the radio uses.
For AM, the noise could be horrendous!

An obvious thing to try: See if you have more than 1 branch circuit
available (in the kitchen, I presume??) If so, plug 'em in on
separate branches and see if this helps. (Note: Won't solve radiated
noise, but might help with conducted - and to me, that seems to be the
problem.)

Unless of course, I totally mis-read your post.

You can also do this test with an extention cord from another branch
circuit elsewhere in the dwelling. Even though the two branches have
at least some components in common, the separation can create enough
losses to lower the conducted emissions to acceptable levels.

Good luck.
-mpm