On Sun, 03 Oct 2010 22:31:07 +0000, Owen Duffy wrote:

I have explored what you have said in an NEC4 model of a quarter wave
monopole with three quarter wave radials at varying heights over
'average ground'. The results are summarised at
http://www.vk1od.net/lost/Clip053a.png . The reference for the graph is
the efficiency of the same antenna with 120 buried radials in the same
soil type.

If the models are correct, laying just a few radials on or very close to
the ground (eg the popular method of pinned into the turf) would appear
to be a very poor option. The model indicates efficiency improves with a
very small increase in height above the dirt, just 30mm is a 6dB
improvement of lying on the dirt, just half a metre achieves 90% of the
available efficiency.

Owen

Owen,

Based upon your findings above, have you thought of increasing the height
of your model to determine at what height would be necessary to equal the
same efficiency as your 120 radial reference?

Danny, K6MHE