After being a ham for 20 years I finally have an opportunity to put up a tower
and a beam. I'm planning on putting up a US Tower HDX-555, and to put on top
of the the tower a Hygain TH11DX. I'd also like to put an OptiBeam OB4030
stacked on the tower at a future date if this is an acceptable load for the
tower. The city I live in, City of Rio Rancho in New Mexico, is in Sandoval
county and the county is listed on Champion Radio Products Tech notes "County
Listings of Minimum Wind Speeds" as a Minimum Wind Speed of 70 mph.
I have applied for a permit to install the tower with the city. When I applied
for the permit I provided a site plan and the Structural Analysis Report from
US Tower for the HDX-555 The city has now requested the tower and antenna load
information for the initial install.
I need to say that I am not a degreed engineer. I am an IT professional and
have been out of school for quite a number of years, and I'm finding trying to
do the load calculations a bit above my head.
I was looking at the US Tower data and see the following -
Basic Wind Velocity: 90 mph 3 second gust, 76 mph fastest mile
Max. Allowable Antenna Wind Loads (lbs): 389
Max. Allowable Antenna Weight (lbs): 200
Max. Allowable Antenna Wind Area (sq. ft.): 23.4 (All round Members)
Max. Allowable Antenna Wind Area (sq. ft.): 13.4 (All Flat Members)
The TH11DX Manual says the following -
Net Weight: 88 lbs
Wind Surface Area (max): 12.5 sq. ft.
Maximum wind Load at 99 mph: 490 lbs.
So I have a few questions:
1.The tower's Max Allowable Antenna Wind Loads is389 lbs, and the
antenna'sMaximum wind Load at 99 mph is 490 lbs. Does this make the TH11DX to
big to put on this tower? I think the tower is strong enough if properly
installed, but am not sure how to convert for the wind speed differences.
2. Which of the Max. Allowable Antenna Wind Area (sq. ft.) numbers do I use?
The round members or the flat members? And are these at 76 mph? How do I get
these wind speeds to match up?
3. What documentation should I provide to the city? Are the specs from US
Tower and the specification for the TX11DX fro the manual sufficient? Or do I
need to use something like the W9JCC spreadsheet to present the numbers?
Any help is appreciated.
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