My speakers are receiving radio signals, how?

[Turkish]

My speakers are receiving radio signals from local radio stations and CBs of people around I asked about it on Off-topic but didn't get a scientific explanation. I have a TV/FM tuner, is it contributing even thought it's not on, or this stuff happens?

 

[uart]

Probably a coil or something in the amplifier circuit (or even the amplifier power supply circuit) is picking up an AM signal and amplifying it. I've also heard of this exact same thing from a freind who lives about 2 km away from a large AM transmitter, though I haven't seen it first hand yet.

Hey dont complain, a set of speakers and a radio receiver thrown in for free.

I'm sure it's not too uncommon to have some small amount of unwanted RF signals picked up and amplified in an amplifier even though ideally it shouldn't happen. I'm not sure how the demodulation happens though, propably not too hard to explain if it's AM but a bit harder to imagine if it's FM. Maybe someone here will have a better explaination of exactly what is happening on a circuit level.

 

[blahblah99]

If your amplifier is poorly designed, then parts of the circuit will act as a tuned-filter and pick up radio signals, amplify it, and send it out to your speakers.

 

[dkozloski]

This is common in audio amps and circuits, particularly musical instrument amplifiers. Check for grounding, corroded connecters, and open shielding on cables. If the power supply plug is two wire, try turning it over in the socket. Poor grounding facilitates the signal being picked up and fed to amplifier circuits where it is detected by any non-linear impedance.

 

[Jeff7]

Nothing from the CIA yet I guess?

 

[JustAnAverageGuy]

My uncle had a similiar problem before he moved.

I think just wrapping something that will block the signal from reaching the wire.

His speakers were pretty cheap as is, and the wires were by no means the thickest ever made.

Try some aluminum foil or something. Cover the whole wire.

 

[Matthias99]

Grr. Double post.

 

[Matthias99]

Ideally what you should do is shield the wire with something that's grounded, as otherwise it may just act as more of an antenna. Aluminum foil would work if you hooked it up to ground somehow. Even just touching the floor of your house might be enough to get decent shielding, so give it a shot.

 

[AmphibSailor]

:music: Two dissimiliar metals joined together (diode) act as a detector. The detector will take the rf and make audio. The speaker plays the audio....

AmphibSailor

 

[jackschmittusa]

The wire is acting like an antenna. Try pulling it through a couple of large hex nuts.

 

[Mday]

Originally posted by: jackschmittusa
The wire is acting like an antenna. Try pulling it through a couple of large hex nuts.

interesting choices for chokes.

 

[beyoku]

that happens to me but i get a CB radio signal! It is cool sometimes cause my friend who sold me the speakers used to talk about the guy. And the guy used to talk about his kids and he was a trucker but had like 10 kids and this was in 1997 - everytime the guy was in Town -MN- We would hear him through the speakers. I would only come in like every week for 5 minutes so it wasnt annoying. This happened for years. I am now in Jersey and i just heard the guy again like 3 months ago! He has 13 kids now!

 

[beyoku]

dp

 

[swank121]

The same thing happens with my speakers, but only if I hold the other end of the wire between my fingers. If it is free or plugged into my comp, I get no reception. Is my body acting like a giant antenna? How can I change my frequency to get different stations?

 

[buleyb]

Originally posted by: swank121
The same thing happens with my speakers, but only if I hold the other end of the wire between my fingers. If it is free or plugged into my comp, I get no reception. Is my body acting like a giant antenna? How can I change my frequency to get different stations?

close one eye and make noises like a duck...

 

[cypriot]

Same thing happens on my headphones all the time, it doesn't happen on my speakers though... I hear some music from local radio stations..

 

[wacki]

Originally posted by: Mday

Originally posted by: jackschmittusa
The wire is acting like an antenna. Try pulling it through a couple of large hex nuts.

interesting choices for chokes.

Mday and jackschmittusa you both seem like you know what your doing around electronics. I know the computer science and I can program AVR's and PIC's, but my knowledge of electronics more basic than that is limited. I have the 3rd edition of "Teach yourself electronics". Its over 700 pages, but the word chokes isn't even listed in the glossary. Basically, my question is do you have a good book you can recommend for me?

 

[Varun]

A choke is another term for an inductor.

 

[Johnbear007]

The devil is putting them there.

 

[wacki]

Ok, choke = inductor, but how does an inductor filter out unwanted radio signals but allow other signals to pass unimpeded. If my understanding of inductance is accurate, the choke would simply smooth out all of the signals giving less accurate audo singals. Or at least, less dynamic audio signals.

 

[dawg548]

As an ex-CBer I can offer you a little knowlege. CB's are limited by the FCC to 6watts of output power. Enough to get you about 2 miles with no interference and not cause any bleed over to other channels since the CB frequency ranges are so close. The problems lies in the fact that most people who are serious about CBs don't follow the FCC guide lines and "open up" thier radios to anywhere from 12 to 55 watts of output power. Then there are those that modify legal ham radio amplifiers to work in the CB frequency range and have outputs from 80 to 3000 watts and higher output. When is the last time you looked at how many watts your speaker runs on? It does not take a whole lot of tweaking to a CB and amp before you are bleeding over the neighbors phones, radios, TV and anything with a speaker. At the 1500 watt and above range I have heard of microwaves talking. I had a friend who was shooting skip on the top of a hill in Texas and unfortunatly missed the local police depatment repeater he was parked near. He shut down all police communications and ended up with ten squad cars and guns surrounding him. LOL Anyway, you can turn the local guy in to the FCC but not much you can do about the truckers. They like to talk for more then two miles and it is hard to triangulate a single moving truck. Good luck.

 

[jackschmittusa]

The choke should impede RF but not the low power audio freqs in the line.