Last weekend I attended a workshop at the ARRL Southwestern Division
Convention given by Tom Schiller, N6BT, President of Force 12. He discussed
many things but antenna height vs. radiation angle was an important one to
me. He suggested modeling various antenna heights and frequencies to check
radiation angle on ones local terrain using YT.EXE from the ARRL Antenna
Handbook CD ROM.
Your situation is probably different, but the program did allow me to
evaluate yagis at various heights. My QTH is on a ridgeline which is 74 ft.
above most of the surrounding terrain. The model indicates
(carefully-chosen word there) I am just fine with a 55' tower vs. the common
wisdom of 66' minimum recommended for 20M antennas. The radiation angle is
very close to the flat earth model at 66' and raising it to 100' didn't do
anthing good as far as I can tell. On the other hand, at 40 ft. the 20M
performance was much worse (higher radiation angle) although 15 and 10M
were not that bad.
Based on this examination, I'm going with the 55-ft. tower and not bothering
with the 72-foot (costly) alternative.
I'm new at this modeling business, but like using the tools of the day. I
imagine the program would allow you to evaluate the alternatives you are
considering as well.
Good Luck!
Roger Gagos, K6EQ
----- Original Message -----
From: <kfath@bellsouth.net>
To: <towertalk@contesting.com>
Sent: Friday, September 14, 2001 2:14 PM
Subject: [TowerTalk] Crank-up towers
...I am not extremely knowledgeable regarding benefit of 89ft over 72ft. ANy
experience or recommendations....
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|