[TowerTalk] FW: Antenna spacing on mast

[Larry]

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 at 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 at contesting.com] On Behalf Of David
Thompson
Sent: Friday, September 14, 2012 2:21 PM
To: Michael Zeglen; towertalk at 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 at hotmail.com>
To: <towertalk at 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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>
>
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