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Re: [TowerTalk] FW: Antenna spacing on mast

To: w6nws@arrl.net, km5vi@flukey.cc, towertalk@contesting.com
Subject: Re: [TowerTalk] FW: Antenna spacing on mast
From: TexasRF@aol.com
Date: Sat, 15 Sep 2012 08:53:11 -0400 (EDT)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi All, running this problem through a mast calculator program shows a wind 
 survival of 93 mph with the following assumptions:
 
1.9" OD .145" wall water pipe
yield strength of pipe 27ksi
pipe length 48"
antenna load 5 sq ft
 
Changing the antenna load to 2 sq ft increase wind survival to 143  mph.
 
73,
Gerald K5GW
 
 
 
 
In a message dated 9/15/2012 6:32:45 A.M. Central Daylight Time,  
lknain@nc.rr.com writes:

Don't  forget about the moment generated by the antenna. Wind pressure of 
100 
mph  is about 40 psf IIRC. That means an antenna at 4 feet that has a wind 
load  of about 182 lbs would deform the pipe at the bottom of the 4 feet 
(based  on your 750 psf figure and ignoring the wind load on the pipe 
itself). At  40 psf  that works out to about 4.5 sq ft of antenna. If the 
pipe  were longer the antenna size would be less for the same effect.

73,  Larry  W6NWS
-----Original Message----- 
From: KM5VI
Sent:  Friday, September 14, 2012 5:57 PM
To: towertalk@contesting.com
Subject:  [TowerTalk] FW: Antenna spacing on mast

It would take a wind pressure  of over 750 psf to bend a 4' section of 2" 
SCH
40 pipe to the point of  permanent deformation.  750 psf is about 30 times 
as
much pressure as  would be generated by a 100 mph wind.  Strength-wise it
would be no  problem for a vhf antenna at this length.  Interference-wise,
the VHF  antenna is really too small to affect the HF antenna even at  close
wavelength.  At VHF, 4 ft is substantially enough wavelength  away that the
HF antenna that it should not adversely affect the VHF  performance.

KM5VI








-----Original  Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On  Behalf Of 
David
Thompson
Sent: Friday, September 14, 2012 2:21 PM
To:  Michael Zeglen; towertalk@contesting.com
Subject: Re: [TowerTalk] Antenna  spacing on mast

Please don't use Sch 40 water pipe even for a VHF  antenna.  Exposing 4 or
more feet increases the chance of it bending  in the wind.  Water pipe
strength is a flow inside not outside wind  strength.
Dave K4JRB

----- Original Message -----
From: "Michael  Zeglen" <kl7ai@hotmail.com>
To:  <towertalk@contesting.com>
Sent: Friday, September 14, 2012 2:42  PM
Subject: [TowerTalk] Antenna spacing on  mast


>
>
>
>
> Want to mount my 2m - 440  small beam antenna above my Pro57B. How far
> shouuld I space it or or  does it really matter as long as there is 3 - 4
> feet spacing. I  realize the more the better. What do you suggest? What is
> good rule to  follow. Sched 40 pipe is NO problem my son is a plumber!
>  _______________________________________________
>
>
>
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