In a message dated 97-02-08 14:43:00 EST, you write:
>As I understand the catalog, the wind load specified for a specific
>installation INCLUDES the 6 cables. Thus, if 100' of 45G, guyed in
>3 places will withstand a wind load of, say 20 sq ft, that means you
>can add up to 20 sq ft of appendages, antennas, etc. These figures
>are all made up to make my point.
Hi, Walt --
Your assumption is basically correct. The Rohn tower loading figure in
the book is the NET result after deducting 1) the square footage of the
cables and 2) 8 sq.ft. of antenna mount at the top of the tower. So your
hypothetical 100 foot 45G has a wind load capacity of: the assumed 20 sq.ft.
+ 8 sq.ft. (the mount) + 23.1 for cables = 51.1 square feet. If you take
THAT figure and start deducting your antennas, mast and cables, then I think
you're pretty close to actual figures.
The antenna mount and specified cables are what would be typical for a
commercial tower installation but doesn't reflect ham applications. By
deducting the antenna mount and the cables in their specs, Rohn has done a
pretty good job of keeping hams out of trouble since hardly anyone has read
the fine print or realized what the implications of all of them are. In
other words, if you use the Rohn figure in the catalog religiously, you're
WAY UNDER what the actual tower capacity is. Safe is good.
> Also, if you only use one pair
>(1/2" & 7/8") cable going up one tower leg you can add an additional
>15.6 sq ft of attchments. Those that sound reasonable?
That's my interpretation as well.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services
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