[Towertalk] Rohn 25G rating

[Bill Tippett]

        One more point for wind-loading which would not affect 
you but possibly others on the reflector.  I belive the figures
given assume sea level.  If you are at a high altitude, you can
derate the conversion from Wind Velocity to Impact Pressure due
to the air being less dense.  As I recall from my Colorado days,
this is about 15% at 5000' evevation.  So, a wind of 100 MPH
there is equivalent to ~85 MPH at sea level in terms of the 
pressure it generates.  I don't believe the EIA Wind Loading 
Zone chart takes this into account.  Those EIA ratings are 
meaningless anyway...at least they were for the front range of 
Colorado where we routinely got 100 MPH and occasional 140+ MPH 
Chinook winds...the EIA chart showed Zone A (lowest winds)!

                                          73,  Bill  W4ZV