Brian Maynard wrote:
>Hi Folks!
>
>For reasons I would rather not recount, I have a bent mast. I ordered
>a replacement from HRO - a USTowers M-20R 2" O.D. x 20' reinforced
>galvanized mast - listing at $259. Turns out the shipping would run
>$600-900! ....
>
I'll bet the shipping is an over-reaction to the increased gas prices.
I have an M15 mast from US Towers. The KSI ratings aren't published. I
called them up and asked for the mast strength rating and was told "they
range from about 35 KSI to 55 KSI". That's about the same range as
common water pipe (as I am told by people who think they know, even
though water pipe doesn't have a rating.) The M15, M20, and M20R are
all the same material, so the KSI rating will be the same, although the
reinforced version will be stronger because of the increased thickness.
The masts sold by Texas Towers and Array Solutions have a much higher
KSI rating.
Do some calculating to figure what you need. Here is a freebie Excel
worksheet you can use to calculate it. Go to
http://www.arrl.org/qexfiles/
and download the file labled TRANVITY.ZIP. Also download the following
pdf file which gives some good discussion.
http://www.arrl.org/qex/1123.pdf
There are other programs that will do this calculation also, but most
are not free.
Jerry, K4SAV
>
>
>
>
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