[TowerTalk] Feed Lines at the Rotator... Best way?

Mark . n1lo@hotmail.com
Mon, 27 Mar 2000 08:17:30 EST

Bill asked:
<< snip...Any hints about how to keep the twisting and stretching of 
rotating the antennas from fatiguing the "flexible" links?..snip>>

Hello Bill,
Yes, indeed. You're definitely on the right track by using your flexible 
jumper between the LMR and the antennas. I like to use RG-213.
I also have three runs of coax going up to the mast. Start by unitizing all 
three flexible jumpers: tape them together in a bundle every 6-8" with 
Scotch super-33/88. Then, form 3 complete turns around the mast at about 8" 
diameter (minimum bending radius for RG-8/RG-213). Then secure them to the 
mast and rout them to the antennas. This is sometimes easier to do by 
attaching the antenna ends first, because this method uses extra coax 
length, and it is very hard to precisely predict the length needed.
The rotation will be spread across three full turns, so the amount of flex 
produced in the cable is greatly reduced.
This setup is perfect for flat-top towers, where the turns can lay on the 
top plate. They will flop around a bit on a tapered-top.

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