Naked Science Forum

Non Life Sciences => Technology => Topic started by: Chemistry4me on 15/09/2009 06:39:58

Title: Speakers that can act like a radio?
Post by: Chemistry4me on 15/09/2009 06:39:58: The speakers on my computer look like this

(https://shop.1wow.com.au/productcart/pc/catalog/cm635_250.jpg)

The other day, I noticed that when I went to adjust the volume, I could just detect the sound of a radio station playing in the background. Strangely enough, this was the same station that I usually have on, but the radio wasn't on or anything. I am wondering how my speakers can pick up the radio channel when I touch the volume adjusting knob? If I remove my fingers, the faint sound is gone. It even happens when the computer is off so it's definitely not coming from there.
Title: Speakers that can act like a radio?
Post by: Don_1 on 15/09/2009 08:03:48: Ah hahahahahaaa, so, my spell is working
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fhalloween3%2F2.gif&hash=b676c96f1ecdf1bcad46b5bce3ba0182)
Title: Speakers that can act like a radio?
Post by: techmind on 16/09/2009 22:29:23: I can almost guarantee that the radio station your speakers picked up is a mediumwave AM (or even longwave AM) station, probably with a transmitter not too many miles away.

It's not unusual for the small-signal electronics in audio circuits to effectively rectify and demodulate strong AM radio transmissions. Because AM radio is so simple, this is all that is required for the audio signal to manifest, be amplified in the circuit, and be heard. When I was younger, whenever I touched the bare microphone input of an amplifier in my parents house in Harrow, north-west London, we heard Capital Radio (now Capital Gold) on 1548kHz AM.

It seems like much the same is happening in your speakers, with your body acting as an aerial even without you touching the circuit input - just getting close. I'd guess the transmitter is fairly nearby therefore.

If you unplugged the speaker-lead 3.5mm jack plug from the back of the computer and touched the tip of the plug with your finger you'll probably get the radio station very loud (in the left speaker).
Title: Speakers that can act like a radio?
Post by: Geezer on 17/09/2009 01:35:21: I agree with Techmind.

Years ago, I bought a Ferrograph tape deck and built my own transistor playback and record amplifiers. The playback amplifier also worked as a really good AM radio receiver under certain circumstances!
Title: Speakers that can act like a radio?
Post by: Chemistry4me on 17/09/2009 06:12:08: Okay, so I'm the aerial. Thanks for the replies.
And be afriad Don_1, be very afraid...
Title: Speakers that can act like a radio?
Post by: Don_1 on 17/09/2009 07:12:47: (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-scared003.gif&hash=51759f83600b800f09deb645ece3b809) (http://www.freesmileys.org/smileys.php) Uhoh!!! Warlocks!!!
Title: Speakers that can act like a radio?
Post by: Geezer on 17/09/2009 07:13:05: Do not fall for the old "Ariel" routine. It's nothing to do with little winged fairies.

It's all about your Aunt Anna. Know, full well, that you cannot mess with she.
Title: Speakers that can act like a radio?
Post by: wanhafizi on 17/09/2009 16:38:34: Have you heard about Lucille Ball's teeth fillings which captured radio signals?

Possible? I don't know...

http://en.wikipedia.org/wiki/Lucille_Ball
Title: Speakers that can act like a radio?
Post by: Atomic-S on 13/06/2010 04:51:25: !
Title: Speakers that can act like a radio?
Post by: tommya300 on 13/06/2010 08:20:06: .
This is possible! Some special conditions need to be met.

[ Invalid Attachment ] (http://www.wiringdiagrams21.com/wp-content/uploads/2009/12/Basic-Crystal-Radio-Receiver-Circuit-Diagram.png)

http://www.wiringdiagrams21.com/wp-content/uploads/2009/12/Basic-Crystal-Radio-Receiver-Circuit-Diagram.png

A tuner is just a coupling 3 passive components, an LRC circuit (http://en.wikipedia.org/wiki/RLC_circuit), a coil, resistor and capacitor.
1 active component to help with the Radio signal and audio signal.
The old concept of a crystal radio and AM signals:

All is needed was a, ground and an antenna (aerial) source, coil, earphones, a germanium diode (http://en.wikipedia.org/wiki/Diode) / (cat's whisker) (http://en.wikipedia.org/wiki/Cat's-whisker_detector); which has a purpose, used as the active device, detector separating the envelope of the signal (carrier wave) from the coherent audio wave.

The concept can be found in documents all over the internet.

Just by touching the volume control, your body, since it does conduct electricity, provides an antenna through a capacitive coupling. The ground source may be your computer or the electric plug to power the speakers. If you lose the signal by removing the speaker wire, maybe this phenomena needs that capacitive coupling to work.
The speaker circuitry components may provide the correct conditions for a functional crystal radio, your body provides the passive signal collector.

Radio transmission has been around since Tesla, well his recorded documentations in exploring in the territory of AC electricity, using LRC circuitry, provided the bases for radio communications.
So don't laugh the concept here with respect to reality, it is feasible!
.
Title: Speakers that can act like a radio?
Post by: FuzzyUK on 28/06/2010 21:37:57: Quote from: wanhafizi on 17/09/2009 16:38:34
Have you heard about Lucille Ball's teeth fillings which captured radio signals?

Possible? I don't know...

http://en.wikipedia.org/wiki/Lucille_Ball

Not proven. It's said she made this claim up as a stunt to gain her publicity.