RadioBanter - View Single Post

Richard Clark · October 20th 08, 08:45 AM posted to rec.radio.amateur.antenna

On Mon, 20 Oct 2008 00:25:00 -0500, (Richard
Harrison) wrote:

With a low audio tone
on an insulated conductor buried in the earth with reference to a ground
rod or ground bed, the conductor can be traced for miles.

During WWI, Heinrich Barkhausen was working with army field telephones
that exhibited strange whistling sounds, unrelated to the war
communications. These sounds were the RF emissions of lightning in
the AF band. What is more interesting is that the mode of propagation
was along Earth's magnetic flux lines, and the scale of propagation
was hemispheric.

As a byproduct of this research, Barkhausen suggested subterranean
communication employing a widely separated pair of rods in the earth,
and driving them with audio frequency communications. Range was
reportedly a function of the distance between the rods. The receiver
used the same earth connection method.

This was the subject of a Popular Electronics article in the mid 60s.

Not reported in that journal, Beverage of antenna fame was working at
the same time trying to develop a reliable RF communication system for
sending orders to troops in the field in Europe, from the US. His
system was a ground level wire of several 10s of miles long, oriented
end-on towards Europe. Troops could hear the US broadcasts in the
field with unsophisticated equipment. However, transmissions back to
the US didn't fare as well. They were overwhelmed on receive by the
back side orientation of the long wire towards the Caribbean and its
summer electrical storms. Dr. Beverage solved that by extending the
wire in that direction too and with termination.

Those frequencies were easily 30 times, or more, higher than
Barkhausen's suggestion - hence the very looooooong wire.

73's
Richard Clark, KB7QHC