> Hope this doesn't cause too much laughter but I keep thinking of that
> graph in the Ant Handbook which shows dipole Z vs height. Could you put
> up a modelled dipole at a known height, measure its Zin and then fiddle
> the model ground characteristics to make the modelled Z the same?
Jim,
The problem with this is the model we use always treats the ground as a
uniform media, and it isn't. Models are shortcuts, they are not real
antennas. They are pretty darned good when a wire is up away from the "mess"
caused by the earth and everything around the antenna, but they are almost
useless for answering questions like "how much wire should I put in what
pattern for an optimum ground".
You read some really goofy conclusions based on people using models outside
limits of accuracy or when they assume "life is perfect". As Jim Lux just
pointed out, there are tests you can do. Many people DON'T do those
common-sense tests and write five page technical papers that reach
inaccurate conclusions.
If you want to know the efficiency of an antenna, you really have to measure
efficiency. It is faster, easier, and much more accurate to just measure
what you need to know than to make 10000 indirect measurements and spend a
year in front of a computer entering the data, just to get an unverified
prediction.
73 Tom
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