[TowerTalk] FW: Antenna spacing on mast

[Joe Subich, W4TV]

You were not only lucky, you were exceptionally lucky.

73,

    ... Joe, W4TV


On 9/15/2012 12:02 PM, k2qmf at juno.com wrote:
>
> 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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>>>> TowerTalk at contesting.com
>>>>    http://lists.contesting.com/mailman/listinfo/towertalk
>>>>
>>>
>>>
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