Yeah.. HFTA sort of builds on Jim Breakall (WA3FET) papers on propagation
modeling - modeling the terrain as a series of parallel plates at different
angles. Sticking with H pol makes the calculations easier because you can
ignore the "left right" tilting (looking away from the antenna in the direction
of propagation) and the reflection coefficient is easier to calculate. So it's
doable on a fairly limited computational platform with fairly simple code.
This is sort of a simplified physical optics and simplified diffraction
approach. (since the diffraction is simplified to a 2D edge between two
rectangular plates).
Today, there's way more sophisticated modeling approaches leveraging much
increased computational horsepower - so people who need to do that can just one
of those FEM packages. That, of course, sort of leaves the "low cost hobby"
market out in the cold. I've taken a look at adding Vpol to HFTA a few times
over the past years, and it's sort of one of those, I'm not sure it's worth it
things.
It's sort of like ionospheric propagation - you can use VOACAP and it's ilk,
which make some simplifying assumptions (Chapman layers, etc.) or you can just
use PHARLAP (which is a full on 3D raytracing).
PHARLAP is free, but restricted - but it also requires a fair amount of
background knowledge to effectively use it.
https://www.dst.defence.gov.au/our-technologies/pharlap-provision-high-frequency-raytracing-laboratory-propagation-studies
(reading that, it looks like the Australian government has loosened up who can
download it now).
On Wed, 14 Jan 2026 22:25:29 -0800, Jim Brown <jim@audiosystemsgroup.com> wrote:
On 1/14/2026 4:43 PM, Jim Lux wrote:
> Too bad that V pol is such a pain to work with - HFTA with vertical pol would
> be a useful tool
Indeed it would. After moving from Chicago to Santa Cruz 20 years ago, I
got to know Dean Straw. He was an excellent contester, and was taking a
turn as President of the Northern California Contest Club, which I had
joined.
I'm guessing it was about 2008 when I asked if he might do that. He
responded that, thanks to his recent Parkinson's diagnosis, he no longer
felt able to do it.
Now, reading that Brian had started it all, perhaps he might take it on.
When I moved here, I'd just gotten back on the air a few years earlier,
so was out of touch with developments in ham radio. Garry Shapiro, NI6T,
caught me up, telling me about Brian's excellent antenna modeling
software and how he'd gotten screwed. Sadly, Garry is another friend
who's been deep into Parkinson's for a while.
73, Jim K9YC
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