From: "Mike Dennison" <mike.dennison@rsgb.org.uk>
To: rsgb_lf_group@blacksheep.org
Date: Thu, 18 Jan 2001 14:00:25 -0000
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Subject: Re: LF: Dipole antenna at LF
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G4JNT wrote:
> Someone must have already tried this, but how effective would a (say)
> 100m long dipole laid down a chalk hill be ? Isn't limestone also the
> same material as chalk,   Are there any CREG members reading this who
> know about conductivity of rocks? Chalk is a very poor conductor, even
> when wet.   A 4m earthing rod driven into the top of Portsdown Hill on
> the South coast of the UK in an attempt to make an RF ground  measured
> 120 ohms to mains Earth - attempt abandoned in favour of a dipole !

I tried something like this in GW in the early days of 73khz but it 
was very poor. Rock may be a poor conductor but it still appears to 
absorb most of the RF. And it wasn't just that my antenna was 
horizontal as in fact it went up a steep hillside at some 30 degrees. I 
tried it again when trying to work MI0AYZ as a deperate attempt 
when my kite failed to fly - it was still poor. Worked fine on receive, 
though.

Depressing as it may be, Marconi got it right 100 years ago and we 
have failed to improve on his findings. There must be another magic 
antenna out there somewhere but that isn't it.


Mike, G3XDV (IO91VT)
http://www.lf.thersgb.net