Reducing Intereference in Your Speakers?

PolicyWonk asks: "I just bought a new stereo, a Sony CMT-EP707, into which I intend to plug my laptop when watching DVDs, and my iPod when listening to music. When I first turned the stereo on I was horrified to hear interference from a local radio station, as well as a general hum emanating from the speakers. The hum and the radio emissions are audible even when the stereo's volume is set to 'min' and irrespective of what setting the stereo is on (i.e. Tuner, CD, or MD), or what input is (or isn't) plugged into the stereo. (I have tried my laptop, iPod, and no input). That means that during a quiet pause in a movie, or the intro to a song, this background noise is clearly audible. No amount of moving the speakers around the room, or plugging the stereo into different grounded outlets seems to fix the problem. I've checked my outlets, and they appear to have a ground connection, but I live on the fifth story of a circa 1900 apartment building in Manhattan, so it's anyone's guess what happens to the wires once they are in the walls. Anyone have any good solutions for reducing or eliminating interference from nearby radio sources?"

Comments

How-To

[the eric conspiracy]

http://www.aca.gov.au/publications/info/cbradio.ht m

Done. Now we can close this topic.

RFI

[Detritus]

It is common for the unshielded speaker wires on audio systems to behave as antennas. The received signals are coupled into the final amplifier stage of the device that is driving the speakers, where they are detected and converted into audio frequency signals that you can hear, sort of like an old crystal radio.

The ARRL has a web page with some information on the subject.

You might ask the engineer at the local radio station for suggestions. Even though it is not the radio station's fault, he may be willing to offer some assistance. Local amateur radio clubs can also be sources of people who are willing to help.

Ask the support department of the manufacturer of your audio device for assistance. They may have technical bulletins on how to solve the problem.

If you are asking people for help, be nice, not confrontational. Remember that it is your audio equipment, not the radio station, that is at fault. Consumer electronic equipment manufacturers could avoid most of these problems by adding less than a dollars worth of parts to their equipment. Most do not, reasoning that it is cheaper to deal with some complaints of susceptibility to RF interference than to prevent the problem.