Dear James and others,
Thanks for your very interesting post. A couple of comments.
> Since the wire mesh would be quite a convenient earth system to use for an
antenna over a paved area, or on rocky ground, I tried laying it on the
concrete driveway:
The mesh might not be as good on a rocky hilltop. There is probably conductive
soil under only 10cm or so of concrete drive, whereas a mountain may be
insulating rock all the way down to Old Nick.
> For portable antennas, it is often difficult to drive long ground rods into
the earth. It seems that short ground spikes, like the tent pegs, or
metallic conductors laid on the surface of the ground, do not make a very
good ground connection.
Have you tried arrays of tent pegs? We meet the same problem with cave radio -
it's normally done on limestone, with very shallow soil, and driving long
spikes in is virtually impossible. What does work well is (say) half a dozen
tent pegs connected together. It doesn't seem to matter much whether they are
in a straight line, a circle or whatever, as long as they are far enough apart.
There are recommendations for the minimum separation, which I forget, but
keeping them a couple of peg lengths apart should be adequate.
For mountain top experiments, there is one comparison which might be worth
trying. One of our cave radio people noticed years ago that Loran reception was
far weaker on peat than on bare limestone. Since she said this, I've often
noticed that it's far weaker on deep soil than on the thin soil over limestone.
Cave radio aerials are completely different from yours, so I'm not suggesting
the difference would be in the same direction. My guess is that you'd get a
better aerial on (ideally wet) peat than on bare rock.
73,
Chris G4OKW
|
