[TowerTalk] Antenna spacing

[K4SAV]

Oops, when calculating those numbers, I had the mast thickness set at 
0.12 (didn't notice it).  I should have used 0.25. With 0.25 thickness, 
antennas at 2 ft, 10 ft, and 17 ft would require a material strength of 
88,000 kpsi to survive 70 mph winds with a gust factor of 1.28. This is 
doable with a good DOM mast, but it is right at the limit.  Chrome moly 
would be a better choice.  An antenna spacing of 7 or 8 ft would 
probably work, but certainly would not be an optimum solution.

Tower ratings are another matter.

Jerry, K4SAV

K4SAV wrote:

>Looks like you have a pretty tall order there. As I calculate it, you 
>have about 20 sq ft of antennas to put on a single mast.
>
>Without considering as to whether the antennas will operate properly or 
>not, but just placing them on a mast for minimum moment, assuming a 22 
>ft mast with 4 ft in the tower (which is kinda sporty), and antennas at 
>2 ft, 10 ft, and 17 ft, you would need a mast strength of 150 kpsi to 
>survive 70 mph winds with a 1.28 wind gust factor. You can get 100 kpsi 
>chrome moly but that's not going to handle it.  This is going to require 
>some serious engineering to put these on a single mast. Then there are 
>tower and rotator considerations also.
>
>Even if you placed the antennas at 2 ft, 6 ft, and 10 ft, it would max 
>out a piece of chrome moly.
>
>Jerry, K4SAV
>
>Jay Rodaman wrote:
>
>  
>
>>I am in the proces of erecting a new tower (60 feet of Rohn45G) and plan to have multiple yagis on the mast.
>>I have a CC402CD, Force 12 4BA and a Hy-Gain 204.  What should the order of placing these antenna 
>>on the mast be and what should the spacing between the antennas be? I would appreciate a responce.
>>Jay
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