[TowerTalk] FW: Antenna spacing on mast

[k2qmf at juno.com]

Mine lasted over 30 years!!!!!

 
On Sat, 15 Sep 2012 09:14:03 -0400 "Joe Subich, W4TV" <lists at subich.com>
writes:
> 
> > running this problem through a mast calculator program shows a 
> wind
> > survival of 93 mph with the following assumptions:
> 
> That also assumes no ice.  Add even 1/4" to 1/2" of ice and the 
> wind
> survival drops significantly.  One doesn't need to be in KL7 to 
> deal
> with high winds and ice simultaneously.
> 
> With multiple antennas on a mast it's not a matter of whether water
> pipe will bend, it is how soon will it bend.
> 
> 73,
> 
>     ... Joe, W4TV
> 
> 
> On 9/15/2012 8:53 AM, TexasRF at aol.com wrote:
> > 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 at 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 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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