Re: Fox hole radio/crystal earphone


From: Mont Pierce (
Date: Fri Sep 29 1995 - 13:37:18 EDT

> You wrote:
> When I was about 8 years old, I built a "fox-hole" radio. It
> used (as mentioned before) a razorblade and pencil-lead (graphite)
> for the detector and a coil of enameled wire around an empty TP
> spool. I already had a crystal earphone, and when connected,
> could tune in two local AM broadcast stations (both within 20 mi.).
> ...
> snip
> ...
> Dale:
> It was my experience as a kid that I could hook just a crystal earphone
> between my antenna and ground and get all the local radio stations (at
> once)! Your crystal earphone may have been the key to the success of your
> early experiment! :-)

Well I don't know about the crystal earphones... But I can testify to the
fact that a razor blade and pencil lead does create a diode. I did the
same experiment when I was a kid. For earphones I use the earplug that
came with a 9v transistor radio.

In this experiment the pencil lead is taped to a safety pin and the safety
pin head bent over and loosely held by a screw into a piece of wood. The
safety pin holds the lead vertically over the razor blade with the weight of
the pin pushing down. You then move the lead around until you make a good
contact on the razor blade and begin to hear AM radio signals.

This is a great experiment for young kids, in just a few minutes with
common materials you can build a crystal set radio :) :)

72, de km6wt

Mont Pierce

+-------------------------------------------------------------------------+ | Ham Call: KM6WT Internet: | | bands: 80/40/20/15/10/2 | | modes: cw,ssb,fm | +-------------------------------------------------------------------------+

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