Hello and HNY,
I haven't posted here since I put my first tower up in 1999 that is still
doing fine. I am considering a second tower of Rohn 25G at 70' with a
single JK Mid Tri. Looking at the Rohn Spec sheets, I am interpreting that
I am in an Exposure B area - Characterized by urban/suburban areas, wooded
lots, or terrain with many closely spaced obstructions (like houses) that
slow wind down.
The JK Mid Tri has the following specs:
JK Mid-Tri
Approx wt. = 98 lbs
Wind Area "C" = 10.6 Sq. Ft
"G" = 19.06 Sq. Ft
Projected Area = 16.0 Sq. Ft
Max Wind Speed = 100 Mph
The Rohn 25G 70' specs shows a 19.4 Sq Ft Allowable Projected Area.
A google AI search on the JK specs had the following:
* Wind Area "C" refers to the antenna's wind area calculation based on
the older EIA/TIA-222-C standard (or similar older standards like UBC-97).
This standard uses the "fastest-mile" wind speed to calculate wind pressure,
which is an average speed over a distance of one mile.
* Wind Area "G" refers to the antenna's wind area calculation based on
the newer, more conservative TIA-222-G standard. This standard uses the
3-second gust wind speed, which is a measurement of the peak instantaneous
wind speed, resulting in a higher (and generally considered more accurate
and safer) calculated wind area for the same antenna.
Should I be using the JK Wind Area or Projected Area to determine if the 25G
is sufficient to support this antenna at 70'.
Thanks for any assistance and HNY,
Jack W4NF
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