Roy Lewallen wrote:
NEC is of course limited to perfectly flat ground of infinite extent.
If the ground slope is constant for a great distance, you can simulate
it by tilting the antenna model the opposite direction then tilting the
resulting pattern. But that's about all you can do. I still use Brian
Beezley's TA program for analyzing the effects of non-flat ground, but
it's long been unavailable and I don't know of any program since which
does the same thing.

N6BV's HFTA program is supplied with all recent ARRL Antenna Books, and
is updated and improved in each edition. For anyone who doesn't live on
perfectly flat ground of infinite extent, HFTA can provide a lot of
answers to the old question: "How good is my QTH?"

However, HTFA is limited to horizontal antennas, and I don't know of any
program that does the same for verticals (it's a much more difficult
problem).


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek