[TowerTalk] FW: Antenna spacing on mast

[Joe Subich, W4TV]

> 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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