Beams/towers

[K7LXC at aol.com]

In a message dated 96-02-10 09:49:30 EST, you write:

<< I didnt realize that there was such a small wind load capability
difference between <25G and 45G--  45G feels like climbing a ROCK compared to
25G to me--- Why is <55G so much stronger?

   Yes,  I was surprised by those numbers myself and decided to look into it.
 Tower legs take all the up and down forces so I compared the specs:

         25G  1.25" OD     16 guage thick
         45G  1.25" OC     14 guage thick
         55G  1.5" OD       11 guage thick

You can see that the 25G and 45G legs are directly related strength-wise
since they are the same OD.  The 55G legs are almost 17% bigger OD with
thicker walled steel.  Increasing the thickness of 25G and 45G legs is pretty
incremental until you increase the OD as in the 55G.  Interesting exercise.

<I need to get that Rohn catalog - great stuff in there - lost mine years ago
- but zeoxed <pages I need from supplier when I installed my 25G - yep -- 25G
when I knew it should <have been 45!!!  

  Get the Rohn catalog from your Rohn dealer or direct from Rohn
(309-697-4400); there are 2 versions, Consumer Products and Commercial
Products - the consumer one has BX and the commercial one doesn't.  They're
$10.00 with a $10.00 rebate.

<I saved some bucks but its just a matter of time that I will pay the
price--- My  25G is <70ft high - mounted in 1 yd concrete, house braket at
12ft, and three sets of guys with <tork bars and equalization plates at
anchors--- 3/16" Rohn with insulators on the two <lower set of guys and 3/16
Philly Stran on top -- whats on this??
<I hate to tell you!!!  get ready for this ----A HS 20ft mast with a
cushcraft 10M 4 elm <beam on top - 10ft down a Force 12 15M 4 elm beam driven
by a Yaesu G1000SDX <and about 10ft below all of that just below the rotor
plate a Tic-Ring with a Force 12 <20M 4 elm yagi on a 30ft boom -- I chose
the force 12 antennas due to their <comparativly less wind loading -----  Oh
well --- It all sayed up in the close call <Hurricanes this summer -- 65MPH
winds--- I think the beams would have blown away <at 80 or above---

   Well, yes your tower is overloaded - Rohn spec says 8.0 sq ft. at 110 MPH
(9.8 @ 90 MPH.)  But they only call for 2 sets of guys of  3/16" EHS at that
wind speed so you have ample guying!  I think your QTH is in Jackson County,
it is a 100 MPH TIA-222-E wind zone; but you already knew that.  Like I said,
when you speed, you don't always get a speeding ticket. Keep your homeowner's
insurance paid up (check into a special rider for your tower system) and have
fun in the meantime! 

73, Steve  K7LXC

     "Up The Tower"    now appears in CQ Contest magazine



>From jreid at aloha.net (Jim Reid)  Sun Feb 11 01:15:49 1996
From: jreid at aloha.net (Jim Reid) (Jim Reid)
Date: Sat, 10 Feb 1996 15:15:49 -1000
Subject: Comparing Radios
Message-ID: <199602110115.PAA25495 at hookomo.aloha.net>

Aloha,  

If you  mean by "hot",  the sensitivity specification,   there should not
be much difference   among like models at HF  At VHF and up,  then 
the noise figure of the front end FETs can make  unit to unit differences.
If the units have the rf and if stages properly alinged,  they should perform
the same,  including if filter performance.  One obvious objection I have
with the import HF transceivers is the many optional filters offered for the
IF strips,  but a lack of engineering of the rigs  to  compensate for the
greater IF insertion losses as the filters get more narrow.  This doesn't
impact front end sensitivity,  but it sure can make if hard to hear weak
signals that are converted to the if frequencies if the IF stage gains
are not hight enought to compensate for the optional narrow filter
insertion losses.

At least these are my opinions.
73 and Aloha,
Jim Reid, AH6NB (Happily retired on the Island of Kauai)
Hawaii,  USA     Email: jreid at aloha.net


>From Fred Hopengarten" <k1vr at k1vr.jjm.com  Sat Feb 10 05:00:53 1996
From: Fred Hopengarten" <k1vr at k1vr.jjm.com (Fred Hopengarten)
Date: Sat, 10 Feb 1996 00:00:53 EST
Subject: Tower Help
Message-ID: <311c2687.k1vr at k1vr.jjm.com>

On Fri, 9 Feb 1996 10:25:01 -0800, "Stan Griffiths" <w7ni at teleport.com> wrote:
> What do you think of this thought experiment:  Suppose I write a tower
> design software program.  I publish it because a lawyer has advised me that
> a "waiver of liability" clause embedded in it will protect me.  Some dunce
> makes a mistake using my program and his tower falls down and kills
> somebody.  I get sued and I lose.  Is the lawyer that essentially advised me
> that I wouldn't be liable for damage due to misuse of my program liable for
> his bum advice and can I recover my damages from him?

Dear Stan:

     You are a very interesting correspondent, because you
are smart, articulate, and disagree with me.  "Yes men" are
far less interesting companions.

     So here's my answer:

     I would feel perfectly comfortable with my level of
risk in advising you to publish the program, if I can embed
a "waiver of liability" clause in my legal opinion.  That's
consistent, legally correct, and financially smart.  In
fact, lawyers write self-help books, computer programs, and
appear on TV and radio all the time, offering advice which
they expect will be followed, all without fear of suit.

     All said and done, however, I have yet to hear why my
parallel to the Lotus 1-2-3 program, as a tool for financial
analysts or lay people, is inaposite.

     I stand by the position I took last time around.  Those
who are nervous, nay fearful, about being defendants in a
lawsuit arising from the publication of a software program
should not be entrepreneurs.  The blood pressure isn't worth
it and the software's author won't sleep at night.  More
fearless types will feel comfortable with the level of
liability risk involved in writing a software program for
designing a tower/antenna system, and, in my opinion, they
should feel comfortable, as the level of risk is highly
attenuated.

-- 
                      Fred Hopengarten K1VR
           Six Willarch Road * Lincoln, MA 01773-5105
     home + office telephone:  617/259-0088 (FAX on demand)
                   internet:  k1vr at k1vr.jjm.com
            "Big antennas, high in the sky, are better
                       than small ones, low."