|To:||"Michael Tope" <W4EF@dellroy.com>,"Pat Barthelow" <firstname.lastname@example.org>, <email@example.com>,<firstname.lastname@example.org>, "Pete Smith" <email@example.com>|
|Subject:||Re: [TowerTalk] Trees, Mountains, 15 degrees...|
|From:||Jim Lux <firstname.lastname@example.org>|
|Date:||Mon, 24 Jan 2005 17:49:58 -0800|
At 05:36 PM 1/24/2005, Michael Tope wrote:
> However, Jim did say "a few miles" away. HFTA, N6BV's terrain analysis > software for the ARRL, only includes terrain out to about 3 miles in its > calculations. The shape of the terrain obstruction can also make a > substantial difference in how much impact it will have. > > All that being said, 15 degrees... wow. > > 73, Pete N4ZR
I believe it is the latter...
In fact, the bottom of page 24 and the top of page 25 of hfta.pdf (Version 1.0) describes manually editing a .pro file to add a big mountain a long way away.
I don't know if HFTA takes into account curvature of the earth and atmospheric refraction, though. While for short distances (a mile or so) the error's only a few feet, when you get out to 10s of miles, the error starts to get bigger. Ignoring refractive effects you're looking at about 30m difference at a distance of 20km... a pretty small angle, though, perhaps a tenth of a degree.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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