David,
Use MicroDEM to extract the Digital Elevation Model for your area. There is an
"HFTA-changes.pdf" document that updates how to get 1 arc-second data, although
you may have to settle for 3 arc-second data (100 meter resolution) in some
areas. But that should be fine for HFTA.
If you have questions, e-mail me direct.
Steve, W3AHL
Message: 6
Date: Wed, 20 Jan 2010 19:15:17 -0500
From: "David J. Sourdis - HK1A" <hk1kxa@hotmail.com>
Subject: [TowerTalk] HFTA question
To: "towertalk@contesting.com" <towertalk@contesting.com>
Message-ID: <COL115-W84625EC1CF28246DE348A8F630@phx.gbl>
Content-Type: text/plain; charset="Windows-1252"
There's a hill that is about 27 meters (90 ft) above the flat surrounding
terrain. Caribbean sea shore is less than two kilometers from this hill.
I guess there is a minimum distance of wavelenghts of sloping terrain required
to take
advantage of such topography regarding antenna take-off angles and HFTA.
In the desired azimuths for contesting, the slopes range (tricky eye guessing)
between 25 and 45 degrees (46% to 100% slope) referenced to the horizontal.
I wonder if it is worth to do some surveying for terrain profiling on said hill
for HFTA analysis or should I just don't bother because the hill's height is
not enough and/or its slope to the flat terrain is too short.
73
David
HK1A
EC5KXA
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