[sammrocks]

I have a 5.1 speakers system I recently bought. When I tested it at the store, everything worked fine, but when I installed it in my living room, I could hear a radio station coming out of my speakers. Does anybody know how can I fix this problem? Thanks.


BTW, I'm a complete newbie when it comes to home theater or audio in general. So, please keep it simple for me. Thanks again.

 

[bpape]

If you are close to a tower, you could be getting leakage through your cabling. You MIGHT be one of the few where quad shield cabling is necessary.


The small thin cheapy cables they give you have very little in the way of shielding.

 

[sammrocks]

Thanks a lot for the quick response . Now, what is quad shield cabling?

 

[Mr.Poindexter]

Back up a minute. Are you running an integrated receiver or seperates? I had my amp chassis picking up a country music station in college. I ended up grounding the chassis and things were fine.


Before you look at new cabling, look at grounding the chassis of your amp or receiver and see if that takes care of the problem. All you would need is to connect a wire from the case of your amp or receiver to a ground wire.


If that doesn't help, then look to your cables, I suppose.

 

[bpape]

Very true. Good thought. I've had separates for so long, I didn't even think about a receiver...

 

[CraigBerg]

Does this issue show up using one particular input over another, or is it constant? If it is input specific, this might point you to a cable or ground loop issue. After insuring that the unit (reciever) itself is grounded. You might try disconnecting external devices to see if this issue goes away. If, for example, you find it to be related to your cable line, you might use an optical isolator to help isolate this issue or confirm that the cable is grounded in your house.

 

[RCbridge]

Speakers and wires cannot pick up modulated signals and demodulate them for you to hear!!

Check any active devices in your chain and follow the advice given above, isolate them one at a time and you will find your leak!!

 

[UMDMatt]

Many people in my office experience the same thing through their computer speakers. We are on the 26th floor (top floor) of a building in Detroit and pick up a station broadcasted on top of 40+ floor building a few blocks away. I'm not an EE but I understand some of this, can anyone explain exactly how this happen when there's not a FM tuner around?

 

[RCbridge]

Quote{{Many people in my office experience the same thing through their computer speakers. We are on the 26th floor (top floor) of a building in Detroit and pick up a station broadcasted on top of 40+ floor building a few blocks away. I'm not an EE but I understand some of this, can anyone explain exactly how this happen when there's not a FM tuner around?}}\\


First have them unplug the speakers from the sound card the audio will go away, which points to the PC itself I don't know how it is configured but something in it is demodulating the signal and it is being heard through the speakers!!

 

[Halveb]

Sorry to bust in but I find this interesting since I have a similar problem.


I have had a problem with a whole house audio system that a radio station bleeds through the speakers and I have always thought the signal was RF interference pickup up by the AC lines acting as an antenna. However you are saying that unless there is a tuner to demodulate that signal you wouldn't hear an audio signal which makes sense.


In my case there is no FM tuner in my whole house audio system though so I cannot imagine what is demodulating the signal. What other components would be capable of demodulating an FM signal?


I have also had the radio station come through my music PA loud and clear using me as an antenna. When I plugged a cable into the mixer (again no radio tuner present in the system) I got a clear radio signal out of the PA speakers.


I will never again buy a property near any broadcast facility due to the strong RF signals present and the effects they can have on equipment. I realize it isn't the broadcast facilities fault if they are transmitting within their power spectrum but my faulty equipment (poor shielding) or possibly AC power supply makes life difficult to say the least.

 

[tvtech1]

"What other components would be capable of demodulating an FM signal?"


Nothing that I know of, AM on the other hand is very easy to demodulate, all you need is a diode.

 

[sammrocks]

Ok. My 5 speakers are powered by the subwoofer. I don't have an amp. It goes like this:


DVD - SUBWOOFER - SPEAKERS


First, I plugged only the speakers to the subwoofer, so there was no line in coming from the dvd. When I did this, there was no radio. It only takes one plug from the dvd to the subwoofer for the radio sound. As I connect the other plugs to the subwoofer, the radio sound becomes louder and louder. I tried grounding the subwoofer chasis, but all I get is a buzzing sound(the radio sound disappears, though). This is really freaking me out.

 

[DoyleS]

As others have suggested, you will have to do some analysis of your system and connections to determine if the problem is related to the DVD player or the Sub system. You can try connecting another source in place of the DVD player (cassette deck, VCR etc) and see if you can hear the stations. Determine what station it is. Is it AM or FM? Most likely it is AM since FM is more complex to demodulate whereas AM can be demodulated by something as simple as a bad connection acting like a rectifying junction(diode action). Depending on your equipment, it may have 3 wire plugs with ground connections or it may only have 2 wire plugs. You may need to experiment with some ground isolating plugs as it does sound like grounding may be part of the problem. Are both the DVD and Sub system plugged into the same outlet? Can you try reversing the plugs in the outlet to see if that makes a difference? If you unplug the DVD player from the wall, is the radio sound still there?


Lots of questions but to get to the bottom of this you will need to go through a logical process of trying different things to see what effect they have on your problem. The Grounding FAQ is also a good place to get some help on hum and other interference. Keep us posted on what you find and we may be able to offer other suggestions.


..Doyle

 

[Version]

I have set up sound systems (not Home systems) that have picked up FM radio signals without a tuner. Just an amp, sound board and speakers.


There is obviously some way to demodulate rado signals without a tuner.

 

[Halveb]

Actually now that I think of it I'll bet it is an AM signal as it seems to often be talk radio and that usually spells AM. I think I will stroll over to the ground FAQ's and try and find some answers. I have tried grounding but this is a household issue as it happened on my PA as well as my whole house audio.


Will be selling the house next summer due to a pending move to another town so I am not too bent up about solving the problem but it would be nice to have the whole house system working reliably when showing prospective buyers the house.

 

[tvtech1]

Quote:

There is obviously some way to demodulate rado signals without a tuner.

for AM, yes, for FM, no.

 

[cmdridq]

I have a similar problem. I'm about a block away from a busy highway and periodically, I'll pick up CB radio transmissions through my TV speakers, and also my computer speakers. Normally it doesn't last more than a minute or so, but it's quite loud. Anyone know of a way to block this out?

 

[Orlando]

I also live not to far from a radio station. At certain times of the day the station can be heard on the speaker for my alarm system and on the telephone that is on the upper level of my house.

 

[Halveb]

In response to the last few posts if you can determine what frequency the broadcasts are on a filter or trap may be able to be installed. In my case I was getting the radio signal bleeding through to my telephone as well. I called the telephone company and once I gave them my address they indicated they knew what the problem was and installed some sort of filter on the phone line. I now get no radio through the phone line but still have problems (I believe through my AC wiring) with RF interference.


Whatever is acting as an antenna if you cancel the offending frequency I believe you can defeat the problem. I haven't found a filter to apply to my AC (if indeed that is where the signal is leaking in). If I wasn't moving in the not too distant future I would be more proactive in finding a solution though.

 

[DoyleS]

The best thing to try is some split core ferrites. They are available at Radio Shack and most amateur (ham) radio stores also sell them.
http://www.radioshack.com/product.as...t%5Fid=273-105


You can place them around the cables or even take a couple loops of cable through where you have determined the interference to be coming from and they will "choke out" the rf signal from the line. If the problem is coming from your DVD player, it is possible that it is entering on the power cord, so a split core on the power cord will often fix this. As described earlier, the basic action is that a wire usually with some length (power cord, interface cable, or sometimes a speaker wire) acts like an antenna, then a poor connection or other component has a diode detecting action and this all usually happens before the final amplification stage. Using the split core, reduces the signal coming in on the wire acting like an antenna so there is nothing to detect and amplify.


..Doyle