[TowerTalk] EIA/TIA-222-E (March 1991) formula

[Roger]

I found it!

There really isn't any difference in the formula for wind load for
appurtenances (antennas).  The main difference is in Table 3, Appurtenance
Force Coefficients.  For an aspect ratio <= 7, Ca = 0.8 for cylinders.  For
an aspect ratio >= 25, Ca = 1.2.  For ratios in-between, use linear
interpolation.  If I read this right, most HF antennas would fall into the
Ca = 1.2 category.  This is dramatically different from the old 2/3 shape
factor!  The effective area spec on our antennas already have this 2/3
shape factor built in, so you might want to multiply by 3/2 to get the
projected area.  Other manufacturers may do this differently.  The most
accurate method is to find the maximum PROJECTED antenna area (either the
boom or the elements only)  AND use the EIA-222-E  formulas.

Also, in section 2.3.10, they added the words "In the absence of more
accurate data," to the beginning of the sentence.

73 Roger WB0DGF
Telex Communications, Inc.
http://www.hy-gain.com
800-898-6723 (orders only)




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