On 1/20/19 12:18 PM, Bob Shohet, KQ2M wrote:
Speaking now about HFTA and K6STI’s YO programs, I won’t go into the
shortcomings of HFTA but rather how they were BOTH useful to me.
HFTA was very useful for plotting the relative time of signals arriving at each
wave angle for a given path and for a given qth and reference antenna. This
was expressed in a bar chart and a line above the chart which made it very easy
to see and understand what arrival angles were most important for Europe, JA,
etc. and then to see a plot of your reference antenna and qth below that. It
clearly pointed out where you might want to make changes in your antennas and
stacking heights to better capture those arrival angles that had the tallest
bars.
This is more of a propagation modeling function, more than HFTA. There's
a lot of very modern propagation modeling software that can run in
real-time and ingest on-the-fly ionosonde measurements. HFTA is using
what are called "climatological" models - what the ionosphere looks like
given SSN, month, and time. This is what VOACAP/ICECAP do (and they are
"state of the art" for that application).
There might well be advantages for hams seeking the edge in running some
of the more modern codes. PHARLAP, by Cervera, et al. is a very
powerful raytracing code, and is probably state of the art, although
there are folks who have "improved" it by adding their own algorithms.
There's also some 3D codes from Naval Research Lab, both for ionospheric
models (which you can feed into PHARLAP) and for propagation.
I have a satellite launched in Dec 2018 carrying a HF receiver to study
just this sort of thing, so I've become aware of a LOT of the latest
work on HF propagation - over the horizon sea state sensing is a big
driver -> you can tell the wind and how big waves are these days using
HF radar. Check out the papers from Barrick, et al, from 30-40 years ago
for the theory, now we can actually make the measurements). Other
spacecraft can tell you ocean surface winds, but they don't tell sea
state very well.
Jim’s example is quite instructive. There is no end to the value of good
modeling programs and learning how to use them properly, especially those that allow
you to model a specific antenna and/or stack of antennas over a specific terrain at a
given qth. $100 and a few hours spent to learn how to use a modeling program, can
repay itself with a 100x or greater pay back in dollars and time saved by being able
to avoid a less effective and/or more costly design/height. There are few things more
fun than enjoying optimal performance of the right antenna(s) at the best height(s) at
your station AND also knowing that at the same time you avoided a costly mistake!
What I'm waiting for is someone to take a high performance ionosphere
modeling code and combine it with maps of amateur radio density and
worldwide lightning noise and create a "better" version of Dean's HFTA
profiles. (Galactic background HF noise is well described by Hilary
Cane's work)
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