Hi Mal,

Thanks for your comments.

On 2010 Jul 18, at 11:14, mal hamilton wrote:
> It would appear what some are using for antennas ie Earth Mode, I am using as 
> a ground system for my Airborne antennas.
> No wonder maximum tx range is very limited. A more straight forward approach 
> to cover the same distance would be a megaphone.

However, we need to bear in mind that running two wires out to tent pegs in the 
ground does more than give you a double Earth connection. They can act as 
effective aerials. For their use in cave radio the propagation mechanism is 
still debated, but they can provide more than earth mode above ground. When we 
were using them for cave radio in the West Riding some years ago, we picked up 
Finbar from Malin Head on 73kHz. That wouldn't have been earth mode. Also, one 
of the problems with cave radio on 87kHz is that it suffers ACI from Loran, and 
the nearest Loran Txs are hundreds of km away.

73,
Chris G4OKW

-----------------------
Dr Chris Trayner
School of Electronic & Electrical Engineering,
The University of Leeds,
Leeds LS2 9JT, United Kingdom
Tel: +44 113 34 32053
Fax: +44 113 34 32032