Re: Experience with odd effects. -Reply

Alan Schneider ( alansch@zip.com.au )
Wed, 30 Dec 1998 17:27:15 GMT

On Tue, 29 Dec 98 16:42:55 -0700, perelman <perelman@ix.netcom.com> =
wrote:

>> On your second item I once hooked up a long wire to a amplifier and=
=20
>>picked up a AM radio station loud and clear. It amazed the heck out of =
me=20
>>since the wire was going to go to a Commodore 64 computer for the =
sound,=20
>>the monitor didn't have sound. The cable was coiled up at the time =
also.

>Is this the same thing as phone wires picking up an AM station? =
Sometimes=20
>I can clearly hear an AM radio station overlaid with a conversation on=20
>the phone (only on my end, the other person can't hear it). The phone=20
>company told me that there was nothing I could do about it, but I've=20
>heard that a choke coil on my side of the network interface should =
reduce=20
>it. (haven't had a chance to try it yet) How exactly is this happening?

Basic mechanism is that of a crystal set. The long wire (or phone lines)
acts as an antenna. Then there is a non-linear component in the =
amplifier/
telephone, or one which is driven into overload by the strength of the
radio signal. This "detects" the radio signal, recovering a small part=20
of the modulation which can then be heard.

A choke in series with the line will significantly reduce the level of
the radio signal. if you're lucky it will be reduced enough to stop
the effect from occurring. A small value capacitor connected across
the line, or from the long wire to ground, may help, too.

hope this helps.

cheers all, and all the best for the coming year.
Alan