----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
>
> Virtually no one can measure localized soil conditions at radio
frequencies,
> and if we could measure it I'd bet there isn't anyone with the time,
> equipment, program, and patience to model it (and we don't know how well
the
> program is verified in that application).
>
> This is just a bunch of wasted discussion because it would be much faster
> and more accurate to measure what you want to know........field strength.
> There is little point in saying something can be done and/or is easy to do
> and describing how to do it when none of us can do it because of the
> enormous difficulty and special hardware required.
>
I don't know that it's particularly difficult to get measurements to a few
percent. Tedious, perhaps, but not requiring any real special equipment. A
standard antenna impedance analyzer would be the measurement tool. You'd
need a few test fixtures, but they're in the "fabricate in less than a day
with simple hand tools" category.
As far as the modeling goes, the theory's all there, and there are some
programs out there that would be a good start. The real question is whether
knowing the EM properties of the soil to a gnat's eyelash (or, even to 10%)
would make much of a difference in predicting the performance of an antenna
system. There are enough other things affecting the model vs reality
situation that it might not be worth it.
I'd venture to say that the vast majority of hams (the ones using modeling
programs like NEC) don't know what the ground characteristics are at any
one place, much less how much it varies in the surroundings.
I would agree that what one wants is really field strength, ideally in a 2pi
hemisphere around your installation. I am working on some non-trivial
hardware to do this, but it's slow going because I've got a "real job" to
worry about too.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|