[Elecraft] OT - The HeyPhone

[David Cutter]

Is it radio?  The Heyphone relied on magnetic coupling between a loop
underground and another on the surface.  At the  time the distance was in
the 100 to 200m range, ie too short to form an electromagnetic wave,
therefore not radio.  It's an interesting subject.

David G3UNA
 

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill Frantz
Sent: 13 July 2018 16:33
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] OT - The HeyPhone

For those that might be interested in further information about underground
radio communications, the National Speleological Society's Communication and
Electronics section has placed back issues of its publication online for
free down load at:

   <http://caves.org/section/commelect/drupal/speleonics>

Some of the European radios have had problems in the US because they are
sensitive to the harmonics of our 60 Hz power.

73 Bill AE6JV