Recently, my 6 year old Klipsch KSW 200 sub started picking up a radio signal. It's always the same station. Around the same time, an inexpensive TEAC unit in my office started picking up the same signal. Not sure if there's any connection, but I recently ran separate phone and electrical lines into my office. Those lines are very close to the TEAC unit. The sub sits about 15' away from the office, through two walls. Any ideas on what I can do to resolve this problem?
It will always be the same station since the cables are acting as a tuned circuit allowing them to pick up this particular frequency. Only by changing the relationship of one cable to another could you alter the resonant frequency of the antenna you've constructed. You can alter the ability of the cables to act as an antenna by lifting the ground connection of the offending cable. Without a ground connection, there should be no tuned circuit. This only assumes the new cables are the source of the problem. None the less, there is a cable acting as an antenna somewhere in these two systems. It would be highly unlikely that both systems would receive the same station unless there were something common to both systems. This could be your new cables or it could be a change in the way or location from where the channel broadcasts. First call the station to inquire whether they have received any other complaints about stray signals or whether they have made any changes to their broadcasting channel of late.
If that doesn't lead to a solution, you'll obviously have to find the source of the problem before you can fix it. At the moment you're somewhat on your own since we don't know the layout of the systems. If the noise began when you first installed the lines, there is a good reason to assume they are the cause of the problem. If the noise appeared simultaneously on both system before or long after you installed the lines, then they are probably not the cause of the noise. If you tell me one system began picking up this channel before you ran the lines and the other system only started to receive this station long after the lines went in, you're screwed!
Begin by disconnecting inputs to the various components. Unplug the line input to the sub and listen for noise when there is just an AC connection. (It is odd for the sub to be playing a radio station since the crossover built into the sub should roll off any frequencies high enough to provide AM reception if they were entering through the line input from the receiver.) Shut down the AC circuit feeding the new lines that run nearby the TEAC unit by flipping the breaker. You'll have to find where the problem originates and then we can give more assistance. As is there are too many possibilites to just start guessing how to resolve the problem.
Thanks for your comprehensive analysis, Jan. Since it is Sunday, I am unable to contact the radio station, but I did follow some of your other suggestions. First, I unplugged the sub to amp cable while leaving the sub plugged into the AC circuit. This stopped the radio transmission. I should mention that the radio transmission will go thru the sub even if the receiver is off, as long as the sub is on and the sub line input is connected. As far as the TEAC goes, I turned off the breaker for the new electrical line, but the TEAC continued to broadcast on the Aux function mode (the same mode I have connected to the computer). The TEAC AC receptacle is just a few inches from my new receptacle. I tried running the TEAC into a receptacle on the other side of the room. This didn't help, probably because the receptacle on the other side of the room is tied into the same circuit as the receptacle next to the new one. So I took the TEAC to a completely different part of the house and plugged it into a completely different circuit and the problem disappeared. As far as when this noise started, my best guess is when I installed the new lines a few weeks ago. I'm guessing that even though the breaker is off, the metal in the lines may be serving as some sort of conductor. Although they are in separate rooms, the new electrical line connects to a subpanel and guess what?...the sub input runs within a few inches of the subpanel on its way to connect with the receiver. So I ran a different input from the receiver to the sub (the existing one goes thru the wall) and and voila...no radio noise. I have enough cable outside of the theater room wall to route it away from the subpanel, thus my only problem now is with the TEAC. Is there some sort of filter I can attach either to the TEAC or the new AC line to resolve this problem? Sorry for the wordiness here, but I wanted to share every step in order to more finely pinpoint the problem. Thanks again!