[TowerTalk] Guying a Self supporting Tower Beyond the Height of Self Support
Bob Shohet, KQ2M
kq2m at kq2m.com
Sun May 6 09:19:41 EDT 2018
Congratulations on your new tower!
A few comments and suggestions...
I have 2 Rohn 45 G towers – one at 100’ guyed at 30’, 60’ and 90,
and big tower of 130’ guyed at 40’, 80, and 120’ – with star guys at 80’ and 120’
Both towers have one leg ~ 8’ – 10’ lower in the vertical plane than the other two legs and both towers have one guy anchor substantially closer or farther away from the tower base than the other two legs. The 130’ tower has one guy anchor ~ 150’ long from the base vs. the other two guy anchors ~ 95’ away. The 100’ tower has one guy anchor at ~ 70’ from the base, one at 90’ and one at ~ 110’ thanks to solid ledge in most places. Highly complex and variable terrain can make guy anchor placement very challenging – the important things is to overbuild (rather than underbuild) with larger bases and guy anchor points and thicker guy wire – this gives additional protection against violent storms and potential failure – and to equalize guy wire tensions.
1) If you are planning to go to 80’, then guy at 40’ NOW.
The guying at 40’ should support 50’ of Rohn 45 with your planned antenna and rotator although it is not advisable, and the difference between 40’ and 50’ will not be that significant for antenna performance. Personally, I would put the tower up at 80’ NOW and guy it and be done with it. THEN put the antenna and rotator on it later. Taking the antenna and rotator off to add sections and then putting it back up is a real nuisance.
2) Since you have a significant difference in elevation in one leg of the tower, I would advise against have the guy points equal distances apart and then having different horizontal components tension to equalize them. The distance from the tower to each guy anchor is less important than having equal tension on them - ideally measured and set with a LOOS tower gauge at ~ 550 lbs for 1/4” EHS guy wire.
3) Take your time and be sure that you are installing everything properly.
73 and GL!
Sent: Sunday, May 06, 2018 8:54 AM
To: TowerTalk at contesting.com
Subject: [TowerTalk] Guying a Self supporting Tower Beyond the Height of Self Support
Greetings all, newcomer here.
Never having done this before, I’m seeking input, ideas and suggestions.
I purchased five - 10 ft sections of Rohn 45G, actually eight.
>From Rohn’s plans for a self-supporting 45’ tower, I followed the plans and stacked the tower to 50’, I know, I know, it’s not 45’!
My wife and I bought and constructed a Mosley Pro67 c3 and and bought an Alpha Spid rotor. All this during the last Michigan winter. We were eager to place the beam atop the 50’ tower and get on the air after a long absence from ham radio, and we thought about going up to eighty feet later. But we changed our minds and decided to go higher and wait a bit longer..
Where do I guy it? Eighty foot Rohn plans suggest 35’ and 65’. But a tower climber and other hams that all had many towers under-their-belt, had other suggestions, i.e., 45’, 75’ and 80', etc. My location is not level ground. The three proposed anchor locations are ~90’ horizontally from the tower. One location is elevated about 8’ , the others are ~5’ and ~10’ below the level of the tower base.
I can get the horizontal components tensions worked out so the total horizontal load at each guying height is balanced, even though the vertical component, on the three tower legs will not be the same, harrumph.
Nuf said. Any suggestions.
Thank you for your time reading this.
Jim Forsman - K7BIE
Linda “Poo” Forsman - K7POO
P.S. We are on a forested 1.5 acre lot in Southwest Michigan.
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