On 6/21/2022 7:37 PM, Billy Cox wrote:
So outside of the cautions Dean shared, and used
with other methods (EZNEC/etc.) why would one not use
HFTA as a useful software tool for stack planning?
Because as KK9A explained, it doesn't model interactions between the two
antennas, which can be considerable. HFTA is a very useful tool FOR WHAT
IT WAS DESIGNED TO DO. Caps for emphasis. These actions come in the form
of currents induced and impedances coupled between elements of the
coupled antennas.
Those who are saying this are well-educated engineers. And Dean was the
editor of the Handbook and Antenna Book when he developed HFTA. Ward
Silver took the reins when Dean retired. I know both men, have worked
extensively with Ward, and both are excellent engineers.
Software like NEC can model antenna interactions, producing a full 3D
pattern over a flat earth or in free space, but it cannot model terrain,
and there's no way to transfer that to HFTA in a meaningful way, because
each of the two antennas interact differently with the terrain depending
on their 3D location with respect to that terrain. FAR more complex
software is required to that, the terrain data must be plugged into it.
One program that MIGHT be useful is called Hobbies.
73, Jim K9YC
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