[Lf] [Fwd: LF: Ground loss/gain (was: polarization of small loops)]

[Andre Kesteloot]

James Moritz wrote:

> Dear LF Group,
>
> The maths required to calculate the gain and Rrad of a loop over a ground
> plane looks much too difficult... so I cheated and used EZNEC instead to
> simulate a 10m square loop 1m above a ground plane - the gain is close to
> 4.77dBi ( ie. 3), instead of 1.77dBi for a loop in free space, so 3dB gain
> due to the ground plane, as one would intuitively expect.
>
> I also tried simulating it with "real" grounds, to find out what the effect
> would be on the radiation resistance. Unfortunately, it does not like doing
> this, giving an error message saying that the resistance is negative and
> the loop is too small. I increased the frequency to 1MHz, where the
> simulation ran OK. Comparing Rrad with perfect ground and free space gave a
> ratio of about 2:1 as expected. With "high accuracy" ground, either very
> low or very high ground conductivity gave lower loss resistance than
> intermediate values, which also seems reasonable - the loss reached a
> maximum somewhere around 100mS, so this suggests that, with actual grounds
> having lower conductivity than this, loops will work best with the lowest
> possible ground conductivity. However, one has to take all this with a
> pinch of salt because of the simulation errors produced if the frequency is
> reduced.
>
> Cheers, Jim Moritz
> 73 de M0BMU