[TowerTalk] FW: Tower height

[Matt]

Hi Mel,

If you are serious about wanting to know, my suggestion is to model your
site installation using HFTA, which comes with the latest ARRL Antenna
Handbook.    HFTA should be able to give you a good idea of lobe patterns
for possible antenna configurations and installation heights as well as
statistical take-off angles for signals arriving from generalized DX
destinations customized for your exact tower location.    The key to that
sentence is "your exact location" because HFTA requires detailed terrain
elevation profiles for meaningful results.   The good news is that there is
FREE detailed terrain data available via download for most all of the
continental US available from the USGS, as well as a nifty Freeware program
called Microdem that can analyze that USGS data and produce reasonably
accurate input files to use with HFTA.  Detailed instructions for doing all
of this is provided with the HFTA program.

You can get a good sense of what the software capabilities are at:

http://www.arrl.org/files/file/Product%20Notes/Antenna%20Book/hfta.pdf

If you decide to go that route, the only suggestions I will add are that (1)
HFTA (as stated) is not antenna modeling software, so antenna performance
characteristics are limited to predefined choices, and (2) performing
calculations with terrain profiles extracted out to 8,880 meters using 60
meter intervals, as opposed to using 4,440 meters using 30 meter intervals,
should give you a more accurate look at the really low angle performance of
your installation.

Good luck on your project!

73
Matt
KM5VI

>>  My assumption has generally been, the higher the better, but I have
wondered if there a good way to verify how high (up to 90') would be the
best for DX?

Things I think factor in:

*       I am on the top of a plateau and have unobstructed views in all
directions

*       My soil is very rocky and slightly uneven (elevation changes about
20' over property) with tower at the highest point

*       It will be a guyed tower

*       The tower will be about 250' from power lines

What would be a good way for me to decide which would be best: 70'?  80'? or
use the full tower 90'?  (I will not go above 90')


Thanks
Mel
N7GCO

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