8mm Forum: My Elmo's a radio,HOW?

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Topic: My Elmo's a radio,HOW?

Tom Photiou
Film God

Posts: 4837
From: Plymouth U.K
Registered: Dec 2003

posted December 30, 2004 12:36 PM

Heres a weird one. A few months ago i was messing around with an ST1200HD i had as spares. I notices one of the single strand wires for the heads was off.As i was only playing and not too bothered about this machine i got out the soldering iron and with patience managed to get the wire onto the head, clearly on the wrong connector for when i switched the sound knob on i was recieving Plymouth Sound radio. the sound was excellent and after i stopped laughing scratched my head in total dis-belief. [Confused]

Can someone tell me how the machine acted as a radio reciever? And a very good one at that, I listened to it for a good 20 minuites before un-Soldering that lead. Spooky.
The Mrs was also well confused. [Big Grin]

(As always)

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Barry Johnson
Master Film Handler

Posts: 358
From: United Kingdom
Registered: Jul 2003

posted December 30, 2004 01:58 PM

Yes Tom,indeed I can.
About a hundred years ago (well forty actually)I was giving regular film shows to local organisationson 16mm sound.One particular showI was setting up the gear and when I plugged in the speaker lead bingo-BBC world service came out of the speaker as clear as day! Mystified by this one of the locals came to me and said this was quite natural in these 'ere parts for we were only fivemiles from the World Servcice transmitters at Daventry in Northamptonshire! The cable acted as a natural aerial.Wait-there is more! When the projector was connected to the mains supply,the sound of the radio disappeared!-Dont ask!
What is more,I was told (and this was confirmed) that by connecting a pair of headphones to the local farm fencing with crocodile clips,this too would give you and adequate signal! You see,the fence was a wire one around his field.An ideal aerial. [Eek!]

--------------------
Standard8 rules!!

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted December 30, 2004 03:44 PM

The input circuit is extremely high gain to handle the very weak signal coming off the mag head. Your wire connection just happened to have a measure to match the wavelength of a local am station. (You can't get FM stations this way FWIW). Years ago and when I was playing around with new amps for my Eiki projectors, I could receive the local (then KDAY) am station in Santa Monica when I put my finger on the metal top of a small electrolytic capactor.

To receive am radio signals all you need is a high gain amp, an antenna and a diode. You lucked out and had all three in your circuit modification. You should check on a schematic and see where your errant wire should be attached and it will likely solve you puzzle.

Besides fences, some people have been known to receive am signals in the fillings in their teeth (especially those that had both gold and "silver" fillings). Again an electrical diode was created that decoded the amplitude modulation to an audio signal.

John

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Tom Photiou
Film God

Posts: 4837
From: Plymouth U.K
Registered: Dec 2003

posted December 31, 2004 07:27 AM

Thanks for, glad i'm not the only one, it did make me think i was going bonkers. [Big Grin]

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