To: rsgb_lf_group@blacksheep.org
Subject: RE: LF: Ground loss
From: "john sexton" <computernetworks@excite.com>
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Date: Tue, 14 May 2002 08:53:32 -0400 (EDT)
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 Hi Sasha,
<br />
I'm afraid this formula gives a result which is an order of magnitude less than measured here.
<br />
Soil conductivity is about 0.002 Siemens/metre (chalk). From notes of one of my test configurations, I had C =233pF, lant = 40.5 metres, lcp = 100 metres. With these figures the formula gives R = 7.7 ohms, whereas the measure value was 93 ohms.
<br />

<br />
Most probably you are considering a flat surface and perhaps an entirely vertical antenna? This may be all well and good for a commercial antenna, but amateur antennas like mine are not on a flat surface, are surrounded by leaky capacitors like trees, buildings, etc. and are only partly vertical.
<br />

<br />
It is common experience among this community that increasing the coverage of ground with wire only works up to a point and beyond that no gains are achieved.
<br />

<br />
See G4FGQ site  http://www.g4fgq.com  for several useful free programs which include information about values of conductivity for different ground.
<br />

<br />
If your advanced formula takes into account the environment, trees, buildings, etc., non flat ground and antennas that are partly horizontal and partly vertical it could be very useful.
<br />

<br />
73, John, G4CNN
<br />
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