I hear voices (sort of)

[Vedran]

Something weird is going on...
My headphones (which I bought a few days ago, made by some German company) are currently plugged in my cheap speakers, which are plugged in my PC. There is no program that is running (I hope) in the background.

The thing is, I can hear some radio-station. The language is German!? The nearest radio-station that could emit in German is probably in Austria, about 200km away (though there could be one closer, who knows).

Is it a commercial trick [img]graemlins/hehe.gif[/img] ? Some sort of: With our earphones you can listen to our radio program everywhere!

Why don't I hear Croatian radios? And why do I hear radio at all? Does the metal band of the headset behave like an antenna? I noticed that it works only if the volume control of the speakers is in one particular position.

Can anyone shed some light on that?

[Timber Loftis]

i'D love to know the answer to this one. Every time I play my computer games my speakers pick up a local radio station. Makes me unplug them half the time.

[Faceman]

It's no commercial trick. It's physics. All you need to receive radio is an antenna and something to transform electric signals into sound. Now the second is what every set of headphones should do. And for an antenna even a TV antenna any piece of metal will do (It helps though if it is a long and slim piece like a cable or an antenna in the common speaking). With my wireless headphones I can hear radio even if no other device in my flat is turned on.

[ 06-04-2003, 04:20 PM: Message edited by: Faceman ]

[pritchke]

Happens with my cordless phone. The ironic part is it usually occurs when I walk around the corner to the front of my fridge in the kitchen.

The signals of food commercials are the worst.

[ 06-04-2003, 04:26 PM: Message edited by: pritchke ]

[Night Stalker]

Also you are picking up the German station on a "hop" of the signal.

[Sir Kenyth]

Ah, my specialty! May I introduce myself as KF4ZHL, my ham call sign. Hopefully, I keep this simple enough. What you are likely picking up is a shortwave station. "Ghost" signals generally need to be from an AM "Amplitude modulated" station. They're quite common. Pick up any old cheap phone without a filter, wait for the dial tone to go off, and you'll probably be able to hear at least one or two faint radio signals getting picked up on the telephone wires. The reason is that amplitude modulated radio signals are the electronic (electromagnetic) equivalent of sound vibrations. An AC electricity in a piece of metal will emit EM waves at the frequency of the current running through it. Modulating the signal amplitudally means that you make the voltage of the frequency higher and lower to reflect the input signal from the voice/music. Since EM waves are generated by AC current, EM waves will induce current in the metal they hit too. It's just a very weak current because of the energy's diffusion over the broadcast area. Radio receivers amplify this tiny current. This just leaves the voltage differences to drive the speakers. The natural properties of many electronic items can mimic this effect on unintentional signals received on their metal parts. The station you hear is dependant on the signal strength and the frequency the item is most resonant with. Particularly strong AM signal sometimes don't even need amplification to drive a tiny ear bud speaker in a well tuned circuit, such as in a crystal radio.

[Stormymystic]

your head phones are possed...quickly dip them in holy water and throw them out

[Animal]

I remember in the days of CB radio, being able to have a conversation with a trucker in Florida while driving between Grande Prairie and Edmonton.

[Night Stalker]

Stormy - it's not possession .......... it's magic!

Animal .... you were able to do that because CB (commercial band) radio is HF (high frequency 500 KHz - 20 MHz apx). HF signals have great ionosphere reflectivity. While you were out of the ground wave (line of sight) of the channel the sky wave bounces between the ionosphere and the ground. Each time the signal returns to the ground it's called a hop.