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Author Topic: Rohn 25g  (Read 1093 times)
KM5PS
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« on: August 26, 2014, 10:55:26 AM »

Will a rohn 25g 100' guyed tower support a 2 ele 40 and 2 th5 tribanders or other tribanders
1 tribander on top and other tribander mounted fixed below somewhere, or maybe 3 tribanders.  1 on top with the 40 2 ele and other two mounted on tower fixed east and west.
Trying to decide on using a 25g or 45g.  I know 45g wud work but cost wud be around 5 to 6 thousand for 45g and hardware. 
2nd option wud be 1 40  2 ele yagi and 1 tribander on a 25g tower.  Thanks for any input or thoufhts.

John
Km5ps
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W8JX
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« Reply #1 on: August 27, 2014, 08:08:17 AM »

Will a rohn 25g 100' guyed tower support a 2 ele 40 and 2 th5 tribanders or other tribanders
1 tribander on top and other tribander mounted fixed below somewhere, or maybe 3 tribanders.  1 on top with the 40 2 ele and other two mounted on tower fixed east and west.
Trying to decide on using a 25g or 45g.  I know 45g wud work but cost wud be around 5 to 6 thousand for 45g and hardware. 
2nd option wud be 1 40  2 ele yagi and 1 tribander on a 25g tower.  Thanks for any input or thoufhts.

John
Km5ps

Its not just wind load and guying it for that load but also the twisting torque together with guy loads and tower/antenna weight that can cause it to screw in and collapse. You want Rohn 45 minimum here.  100 ft with one nice tribander would be okay on 25g but that and a 40m beam is pushing it.  Sure you could add torque straps but not a real fix. If you really want all the hardware at 100 feet get 45g. Now two antennas at 60ft of 25g should be okay with proper guying.  I knew a guy that went to 130 feet with old Rohn 20 that I helped erect but it just had a repeater antenna and no torque load and we use a tensionometer to set guy loads too.
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W9FIB
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« Reply #2 on: August 27, 2014, 09:34:59 AM »

The Rohn website has lots of information. I doubt even Rohn could design a system with that much wind load and torque for 25.

I personally would never put that large a load at that height. 25 is just not built for it. If your going to put up a big gun system, you really need a big gun tower. 25 is more for the little pistol systems.
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KM5PS
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« Reply #3 on: Yesterday at 06:46:46 AM »

Thanks for the advice.  I think that I am going to try to put up 2 tribander's boom length of 24' and a rotatable dipole for 40 meters above the top tribander.  1 tribander and the top and another one 30 feet below that mounted to  the tower and the 40 mtr dipole about 6 feet above the top tribander.  But that may still be too much torque for the the tower.

Thanks again
John
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W8JX
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« Reply #4 on: Yesterday at 07:31:21 AM »

Thanks for the advice.  I think that I am going to try to put up 2 tribander's boom length of 24' and a rotatable dipole for 40 meters above the top tribander.  1 tribander and the top and another one 30 feet below that mounted to  the tower and the 40 mtr dipole about 6 feet above the top tribander.  But that may still be too much torque for the the tower.

Thanks again
John
[/quote/]

It is at 100 feet. Unlike vhf/uhf you do not gain that much above a certain height.  60 gives you a 1/2 wave on 40 and 1 wave length or more above ground on 20 and above and it will play well.
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