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## Re: [TowerTalk] FW: Antenna spacing on mast

 To: k2qmf@juno.com Re: [TowerTalk] FW: Antenna spacing on mast "Joe Subich, W4TV" Sat, 15 Sep 2012 12:54:34 -0400 mailto:towertalk@contesting.com>
 ``` You were not only lucky, you were exceptionally lucky. 73, ... Joe, W4TV On 9/15/2012 12:02 PM, k2qmf@juno.com wrote: `````` Mine lasted over 30 years!!!!! On Sat, 15 Sep 2012 09:14:03 -0400 "Joe Subich, W4TV" 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@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@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" To: 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! `````` _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk `````` _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ``````_______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk `````` ____________________________________________________________ Woman is 57 But Looks 27 Mom publishes simple facelift trick that angered doctors... http://thirdpartyoffers.juno.com/TGL3141/5054a68eeeaa2268e0a38st04vuc _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ``````_______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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