Re: geography nerds?

On Fri, 22 Feb 2008 16:30:34 +0000 (GMT), dbell@[EMAIL PROTECTED]
("David G. Bell") wrote:

>This is, incidentally, how a crystal set works. A very strong radio 
>signal (helped by a long aerial), a diode as detector (the original 
>crystal), and the headphones which only responded to the audio. Oh, an a 
>tuned circuit so you could listen to a particular transmitter.

Don't even need a tuned circuit; as i recall reading, various spots on
the crystal can react somewhat differently.

I once read a "scientific things to do for kids" book which included
making a "crystal radio" out of a blue steel razor blade, a pencil
lead and a safety pin.

John W Campbell once published a little squib in Analog which claimed
that US Navy radio operators using crystal sets Way Back When had
discovered that adding a second "cat whisker" contact wire and feeding
a low DC voltage to it improved reception - they had no idea why, and
apparently it was an accidental discovery.

What iw was basically an application of the transistor principle
thirty or so years before the invention of the transistor.