Am using ANTENNA MODEL and would like to model a sloping ground surface
under my longwire V. Any ideas, or is there other software that does
this?

Had you thought of modeling it as a sloping antenna over level ground?

"Alex AG0Z" wrote in message
oups.com...
Am using ANTENNA MODEL and would like to model a sloping ground surface
under my longwire V. Any ideas, or is there other software that does
this?

I have thanks. I'm just not sure of the elevation results.

Think Brian, K6STI used to advertize a program modeled over
TRUE ground (like topo map, ect). Dont know if he still
sells it, however. (That for antenna patterning , H.A.A.T.)
As info, Jim NN7K

Alex AG0Z wrote:
I have thanks. I'm just not sure of the elevation results.

The program you're referring to is probably Brian's TA (Terrain
Analysis). It gives you the antenna pattern over an arbitrarily shaped
ground -- I've used it for many years in choosing Field Day antenna
locations. It's a DOS program, but I don't know of any more recent
program that does the same thing. I believe Brian will still sell it if
you contact him by mail at his Callbook address.

TA requires as its input a free-space pattern in the OpenPF format he
devised (with some help and advice from me). EZNEC and Brian's analysis
programs like AO produce plot files in that format. It's thoroughly
documented in the EZNEC manual, so it wouldn't be difficult for someone
with minimal to moderate programming skills to convert files of other
formats to OpenPF for use by TA.

For the OP, though, if the ground is simply constantly sloping for a
long distance, do as suggested -- tilt the antenna in the model. Then
tilt the resulting pattern in the opposite direction to see the result.

Roy Lewallen, W7EL

Jim - NN7K wrote:
Think Brian, K6STI used to advertize a program modeled over
TRUE ground (like topo map, ect). Dont know if he still
sells it, however. (That for antenna patterning , H.A.A.T.)
As info, Jim NN7K

Alex AG0Z wrote:

I have thanks. I'm just not sure of the elevation results.

Roy Lewallen wrote:
The program you're referring to is probably Brian's TA (Terrain
Analysis). It gives you the antenna pattern over an arbitrarily shaped
ground -- I've used it for many years in choosing Field Day antenna
locations. It's a DOS program, but I don't know of any more recent
program that does the same thing. I believe Brian will still sell it if
contact him by mail at his Callbook address.

The HFTA program included with the last two editions of the ARRL Antenna
Book will do most of what TA does, and is a Windows program.

A unique feature of HFTA is that it not only calculates the vertical
pattern over your real-life ground profile, but also shows how well that
pattern agrees with the likely angles of arrival of signals from various
parts of the world - which is, after all, what really matters.

The HFTA User Manual is available as a free download from:
http://www.arrl.org/notes/9043/hfta.pdf

The program itself is free if you've bought the book... which is highly
recommended in its own right. Also, you really need the book to
understand the concepts behind the program.

The manual includes a very long section detailing how US amateurs can
tap into public-domain map databases, to generate detailed height
profiles in selected radial directions around any arbitrary QTH.

The rest of us have to generate the terrain profiles using a paper map,
ruler and Notepad. This is tedious, but poring over a detailed map can
teach you a lot about your local geography, and the job only has to be
done once (unless you're surveying several possible sites, as Roy was).


TA requires as its input a free-space pattern in the OpenPF format he
devised (with some help and advice from me). EZNEC and Brian's analysis
programs like AO produce plot files in that format. It's thoroughly
documented in the EZNEC manual, so it wouldn't be difficult for someone
with minimal to moderate programming skills to convert files of other
formats to OpenPF for use by TA.

Unfortunately HFTA doesn't read OpenPF files. It only allows the choice
of predefined vertical patterns for a dipole, or for generic
"2-element", "3-element" and larger beams, or for stacks of beams.

This restriction isn't a huge problem, because the major features of
your vertical pattern depend much more on the antenna height and the
terrain profile than on the antenna itself. That means the "closest
generic" antenna pattern will give a very good approximation.

However, it would be nice if HFTA could read the vertical pattern of
your or my favorite antenna, so that we could confirm that fact for
ourselves.

Another acknowledged limitation is that both HFTA and TA can only be
used for horizontally-polarized antennas. Doing the same for verticals
would involve major complications about pseudo-Brewster angles... a very
much larger can of worms.



--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek