[TowerTalk] Antenna & Tower Wind Load Ratings

[Roger (K8RI) on TT]

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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