[TowerTalk] Terrain Modeling (was choke on vertical dipole)

[David Gilbert]

FEKO is supposedly a much more sophisticated modeling application 
capable of handling complex terrain and even 3D objects like cars (or 
tanks, for which I assume it was originally designed) and at one point 
it offered a free download for students and experimenters if you 
registered with them.  I downloaded it and tried to use it, but 
eventually decided that the effort it would take to learn it greatly 
exceeded the practical benefit I would get from it.

Dave  AB7E


On 1/15/2026 11:13 AM, Jim Lux wrote:
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>
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> 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).
>
>
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> On Wed, 14 Jan 2026 22:25:29 -0800, Jim Brown <jim at 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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