-----Original Message-----
From: Dubovsky, George
Sent: Wednesday, March 18, 2009 1:48 PM
To: 'Scott McClements'
Subject: RE: [TowerTalk] HFTA Accuracy / Usefulness
Hi Scott,
I have been doing a lot of HFTA'ing recently, doing analysis for a
planned third tower. I look at the program as a statistical tool, far
more important to a contester than a DX'er. It gives valuable insight
into what "local" terrain and angle of arrival really mean to your
station performance. If you just want to work a new one in the Pacific
when it comes on the air, the higher-is-better rule is probably OK. If
your goal is to maximize rate into EU several hours after the band has
opened, then the insights available in HFTA start to become more useful.
In your case, it may tell you to put up your tall tower, put the 40 on
top, and put a tribander down a little lower on a ringrotor.
As a rough data point on the general accuracy of the program, I operated
a lot and contested quite a bit (in the 70's and 80's) from a suburban
location about 15 miles from my present farm qth. I had one 105' tower
behind the house with a shorty-forty at 115' and a KT-34XA below it. I
used to run really well into EU and AF, and not so well into SA and JA.
About two years ago, just for grins, I calculated the MicroDEM radials
for that old station and ran them on HFTA. Sure enough, I had golden
terrain falling away for several miles towards EU, a ridge 1/4-1/2 mile
away towards JA (that was taller than I ever thought when I lived there)
that was killing my low and moderate angle stuff, and I was too high for
SA most of the time (except on 40).
Bottom line: good tool, will tell you things that you need to know,
won't tell you everything you need to know.
73,
geo - n4ua
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Scott McClements
Sent: Wednesday, March 18, 2009 1:23 PM
To: towertalk reflector
Subject: [TowerTalk] HFTA Accuracy / Usefulness
Hi All,
I've been in several discussions with some local contesters/DXers over
the High Frequency Terrain Assessment (HFTA) software included with
the ARRL antenna book. I have used the program myself several times. I
was a bit surprised when a local had chosen his new tower height
solely based on the HTFA assessment. He had purposefully chosen 78
feet over even higher heights because HFTA showed that higher heights
actually raised his angle of radiation towards Europe. There would
have been a limit to his tower height at some point, for aesthetic and
neighbor relation reasons, but I don't think momentary reasons.
This brings me to my main point. I went back and read the HFTA
documentation looking for statements about its accuracy. The author
doesn't try to oversell it accuracy (+/-3dB), but its clear not much
has done to validate its results. So the question - Is there any real
value to this tool?
My opinion was that I would go as high as I could despite what HFTA
said (esp. since it will include a 40m yagi). Perhaps I am wrong - I
was curious what the consensus was. I am asking this with all due
respect - I know there was much effort put into this tool and it uses
the technology and information we have available to us today to the
fullest.
-Scott, WU2X
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