Hi I agree it could well be that coaxial but have a load of
There are two possible ways the radio is suffering interference,
either "conducted" or "radiated," according to Jim Nelson, senior
project engineer at Illinois-based Oneac, a company that makes
products that provide protection against power and data-line
"Conducted" means the interfering radio frequency noise is flowing out
the power cord of the PC and up the power cord of the radio.
"Radiated" means the interfering radio frequency noise is being
emitted directly from the PC or cables connected to it through the
air, just like a radio station.
"It's true that a PC sends a much weaker signal than any radio
"It is infinitely closer, as far as the radio is concerned, so the
noise wins," said Nelson
First, try a battery-operated radio in the same location and tune it
to your regular station. If the interference goes away the problem is
likely conducted, though this is no guarantee. The portable radio may
be better filtered.
If you think the problem is conducted, plug the radio into a different
electrical circuit than the one the computer is on.
Or try using a line filter on the PC and radio. Look for
transformer-based Uninterruptible Power Supplies (UPS) that filter out
noise and protect against surges. (Oneac makes them, said Nelson.)
Look for one that has built-in filters for Radio Frequency
Interference/Electro-Magnetic Interference (RFI/EMI) and that has high
isolation rating (in "db" or decibels).
If the problem seems to be radiated, first try repositioning or
re-orienting both pieces of equipment and their cords.
Some radios use the power cord as the antenna. The cables coming out
of the PC can work as antennas, too. A device at the end of the wire
doesn't need to be in use or even on for the cord to be a problem.
Turn the PC and radio on so you can hear the interference. Start
disconnecting the cords from the back of the PC one at a time to see
if one in particular is causing the problem.
The problem may be caused by several sources.
So the interference may diminish slightly if one cord is removed. You
can't pull the power cord, but it may be the source, so don't forget
it when you try some of the following suggestions provided by Nelson.
- If there are screws on any of the connectors make sure they are
tight, as some shielded cables require them for good grounding.
- If you suspect some of the cables going to your printer or serial
device are unshielded, go buy replacements that say shielded wire is
- If any cables are longer than they need to be, bundle and tie them
Don't roll them into a coil. Weave them back and forth as tightly as
possible and tie or tape them.
- Ferrite cores or beads in a cable can help at certain frequencies.
These look like a small cylindrical lump near the connector. Your
monitor's video cable probably has one.
Snap-on versions can be bought at places like Radio Shack. Try them on
the cables that you suspect.
They work best nearest the source (the PC main box), though sometimes
sliding them up and down the cable changes the effect.
If the hole in the bead is large enough, loop the cable more than once
to increase effectiveness.
- Sometimes long slots or breaks in the metal PC cabinet can act as an
antenna. Make sure the PC cover is seated properly and screwed on
tight, if you have ever taken it off.
If there are still long openings in the box try to seal them with
aluminium foil tape sold at heating and air conditioning suppliers.
Don't put the tape near electrical connections or use it where it
could fall on something that has power running through if it came
Also, be sure not to cover openings used for ventilation. The tape
trick is a last resort.
"It's rare that this is the source, but I've seen it work," said