I can suggest taking a look at the MMANA-GAL and 4nec2 programs. MMANA-GAL
may be more user friendly but 4nec2 is more versatile. These are both
available for download - just Google search. Both will model sloping ground
effects.
IMHO the question really becomes the economics of low wave angles. You may
find VOACAP (and it's datives) useful for predicting what is achievable for
a given wave angle - Google search for ITS HF Propagation. You will want to
also look at the user forum online as this program requires proper inputs to
get meaningful outputs.
The economics become band dependent - for example, the cost to go from say
75 ft to 120 ft might typically be a factor of 200% (or more), and on 14mhz
and higher the wave angle benefit may not justify the incremental cost for
your intentions. However, on 10mhz & 7mhz that could be a completely
different story. All depends on what you want to achieve.
73 to you in your endeavors.
KM5VI
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Andreas Hofmann
Sent: Wednesday, November 30, 2011 6:48 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Determine cost-effective tower height
Hi,
I have decided I need a tower to get better antennas up in the air. Thinking
about the SteppIR DB 18, 40m 2 el, 20 and up 3el. Now, my property slopes
pretty much in every direction by 5 degrees. I need to determine a proper
tower height without breaking the bank.
I was told I should run a computer program to figure a good height of the
yagi for my most important directions/DX locations. In fact a friend of
mine did the same (on a similarly sloping property) and he found out that a
55 foot tower would be similar to a 120 foot tower on a flat ground. Hence
he put up a 55 foot crank up mast and it is rocking. He forgot the program
he used.
So, what tool can I use to find the optimal (not maximal) height of a tower
that would work well here?
Also, the tower would be setting on the side of the house with a metal roof
(roof about 15 feet high), not sure if this would matter...
Thanks
Andreas
KU7T
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