Just write a formula for the wind speed Vs height, which is more or less
linear with exceptions with heavy woods and close by buildings. Do the
same with crank-ups where ea section is a constant size, but different
from the others You can do sections and add the results . Formulas can
be combined as well.
I "used to be" good at deriving formulas, but made mistakes (usually
dumb mistakes) with the numbers.
In grad school, (Computer Science) we had to write algorithms, then
convert them to a mathematical formula.
This is "similar" to antennas and towers. That similar is important,
meaning it's almost the same, but different.
Over engineer is usually the safe way<:-) That's why I like the flat
plate area for antennas.
73, Roger (K8RI)
On 6/15/2017 Thursday 3:57 PM, Clay Autery wrote:
Sounds like a definite improvement.... Don't forget the caveat for the
tower folks that needs to be included about feed-lines, control cables
at al. An LMR-600 or 900, 1200, etc. feed-line is a significant
projected area... Can't imagine the integral you'd need to use since
the effect would need to be weighted against altitude...
For now, I'll just continue to over-engineer and over-specify like I
always have. :)
73,
______________________
Clay Autery, KY5G
On 6/15/2017 11:56 AM, JVarney wrote:
The core problem here is the ham consumer is not being given
compatible and concise data from which to make an informed choice.
There's only one way for antenna ratings and tower ratings to fully
compatible and that's through the "Aa" projected area term in
TIA-222-G. Antennas and towers should be rated like this:
===
TRIBANDER MODEL XYZ
Aa = 11.0 square feet*
* TIA-222-G 100mph wind speed, height 100 ft, Exposure Cat B, Risk
Category I, Topography Cat 1.
CRANK-UP TOWER MODEL ABC
Max capacity Aa = 16.0 square feet*
* TIA-222-G 100mph wind speed, height 70 ft, 75 lbs. weight,
antenna 3 feet above tower top, Exposure Cat B, Risk
Category I, Topography Cat 1.
===
"Aa" provides the "Apples to apples" linkage between tower
and antenna. Maybe that's why they chose Aa as the name of the
term :-)
I have no connection to or business with AN Tower but I commend
them for publishing full and complete 222-G tables for their products. They
rate their towers by Aa square footage.
The industry standards are there. It's a matter of coaxing the
manufacturers of both towers and antennas to label their products
accordingly.
73 Jim K6OK
===
Kurt Andress: "There are basically two types of "Antenna Area"
values to be considered....."
Jim Lux: "Tower mfrs cite a "X square feet" as opposed to
a "X lbs load"
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73
Roger (K8RI)
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