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Tower Loading ... (long)

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Subject: Tower Loading ... (long)
From: (Billy W. Cox)
Date: Thu, 06 Feb 1997 17:15:06 -0800
Play nice guys ... <grin>

Here's my 2 cents on this after 25 years (gasp has it been that long!)

We are "amateurs", but there is NO PLACE for an "amateur tower setup" !

You build an rcvr, xmtr, amp, etc and it "doesn't work", no big deal
as compared to a "amateur tower setup" that "doesn't work" and comes
down ... Too many risks to consider a "amateur" TOWER installation ...

What will Rohn products "really" hold ? Who knows ...

But will it hold what they state in their 'gobbly-goope' ? YES, and 
with a margin that will let you sleep at night without worry.

I have several Rohn books (both big and little ones) and in fact
just ordered another to see what they have changed. The more you
look into ALL the various combinations, the more you will learn.
Like the 80' 25g setup with a dish on it and the guys spaced at 40'!! 
But be very Very VERY careful. That ONE example does NOT mean YOU
can load YOUR 80' of 25g up with 45 square foot of antennas and
say "meets Rohn specs" ! Did you notice for that PARTICULAR setup,
they use 1/4" EHS for the tops guys, 3/16" for the bottom set and
that the specs for the guy anchors was MUCH LARGER than 'normal' 
Ooooo, and that you MUST use the special (read high buck) torque
doie at the top ? (I'm doing this from memory, there may be errors)

"Billy the cheap-skate amateur" looks at that and says "he**, I can
get away WITHOUT that high dollar torque thingi, and Bubba has some
guy wire left over from putting that TV antenna up, but it's only
enough for one set of guys ... shoot that TH6 and shorty forty ain't
as big as that there dish in the Rohn picture ... so we'll just guy
it oooo about 50' up (80' tower remember) ... BTW, Billy is using a
big-o water pipe for the mast ... I think by now you get my point ...
(and for anchors, they dug "a hole" and used a few bags of quickcrete)

First wind of the season and down it all comes. Insurance folks come
and see. Billy says " Oooo I followed the Rohn specs ...." Yea, right !!

No wonder Rohn doesn't give free advice ... to "amateurs" ...

I'm NOT a PE. But anyone who is planning a tower needs to understand
what the "bending movement" is and what the guy AND guy anchor specs
are for the tower involved. It will take some study in the Rohn books
to find and understand it. Look CAREFULLY at what Rohn shows and does
NOT show. 80' of 25G with a TH7/40-2CD is going to need THREE sets of
guys to NOT exceed 'specs' IF the 40-2CD is mounted 12' ABOVE the TH7.
(35' MAX between guys and then you have to watch the bending movement
above the top guys, so it will have to be guyed at 26/52/78) And that's
for a MIN installation ! Higher wind areas may require guys closer than
35' for ANY setup ... READ THE BOOK !

Other items, such as guy spacing and guy radius may need to be
INCREASED if you intend to mount other antennas and turn them ! That's
a situation where Rohn says 80 %, but you may need to go out further to
allow that sidemounted antenna to turn ... PLAN IT OUT !!!

Putting it all up it easy as compared to PLANNING it all out before.

IF you don't understand all this, PLEASE get someone else to look over
what you are doing, and have THEM put it up ... NOT YOU !! We read/hear
too many times about "sk's from tower falls/failures". 

I've gotten OLD, but wiser I hope. I don't climb other towers unless I
know how it was put up. I don't do things I know exceed 'specs' that
I consider safe. A friend of mine RODE a 70' 45G tower DOWN a few 
years back. It was a commercial site, he was checking a UHF array for
a commercial customer. He DID not put the installation up. A guy was
loose at the CLAMPS and a gust came up ...guy pulled thru the clamps
and the tower came DOWN as the tower base used a pin that was *again*
not a proper setup. JR broke both arms/etc/lots of bills/etc and
then "retired" from commercial radio work ! In hind site, he knows he
should have never set foot on it, but his boss told him too... He was
DAM* lucky to live thru it. Will you be ????

I use ONLY Rohn stuff, and I don't worry. One tower has been up for
14 years, the other about 12. "Saving 4 bucks a turnbuckle" is NOTHING
when averaged over the life of the installation. I once REFUSED to
set a tower for a friend when he showed me the hardware he had purchased
to use ... I looked at the cheap AL turnbuckles and cheap clamps and
told him to call me when he was SERIOUS about putting up a tower ....

Reality is that one is NOT going to be able to install KS9K/W3LPL size
antennas on Rohn 25G, No matter how you "figure/calculate/guess/push"
Big antennas take BIG towers and that requires LOTS of space and
MONEY ... any short cuts taken will tend to bite you on the butt !

Now, years later ... I WISH I had used at least 45G. The 25G limits
me as to what I can REALLY do "out back". The difference in initial
over the years would have been NOTHING. To start over today here is
not practical, perhaps the NEXT site will begin with 45G ... Sure I can
put bigger antennas up NOW ... but I know better ... and won't ...

Well there's my 2 cents, with change left over ... 


Why ? I need all the contest Q's I can get and SK's don't count !

73 Billy AA4NU

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