[TowerTalk] HFTA question

Steve, W3AHL w3ahl at att.net
Wed Jan 20 18:35:38 PST 2010


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 at hotmail.com>
Subject: [TowerTalk] HFTA question
To: "towertalk at contesting.com" <towertalk at contesting.com>
Message-ID: <COL115-W84625EC1CF28246DE348A8F630 at 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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