Nacho wrote in message ...
Hello.

I need some help from you.

I live in a big city and shortwave is very noisy. But the main noise
comes from my own house, specially the computers.

I have been trying to reduce the interferences using ferrite and iron
powder chokes.

I have been playing with two kind of chokes: one is the typical toroidal
iron powder, painted choke, and the other is like a ferrite choke in a
hollow cylinder, divided in two part in a plastic case, that can be put
in a cable without disconnecting it.

Some noises are reduced best when I use the torodial choke (like in the
AC currect cable to the receiver) and other noises are reduced with the
cylindrical choke (like in the computer cables, specially the keyboard).

I prefer the cylindrial ones because it is much easier to put. For
keyboard cable, it works great, so I plan to buy some in a electronic shop.

Can you give me some recommendations about them? I want to buy some big
and some small (if they are cheap, I don't know the price). For the
keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more with one
cylinder the noise is reduced but doesn't disappear, as it is much nearer.

Any recommendation will be great.


Thanks a lot.

It might be well worth your time and saved money to find all the local
shops that work on PCs. A lot of dead PC subsystems will have ferrite
that can be used for RFI/EMI control. Most monitors have a big ferrite
choke on the video line. And have several more inside. Dead switch
mode power supplies often have several ferrite chokes inside them.
Even keyboards and mouse often have ferrite chokes inside. I have
salvaged many usefull pieces of ferrite from otherwise useless and
dead PC "stuff".
Even modern consumer devices like CD players, TV sets, heck, almost
anything
with a micro-controller inside will have at least one ferrite choke
inside!
Good luck and happy hunting!
Terry