[TowerTalk] Coax Feedlines

[Roger (K8RI) on TT]

Consider this as a starting point.

With low power and only 100' run, most any good coax will do for HF.  
For VHF and UHF, LMR400 will have the lowest loss as long as you don't 
need flexibility. if you need flexibility then BuryFlex (TM) is a good 
choice with only a little more loss than LMR400. Don't get LMR400UF.  It 
is the most flexible, but not prone to long life out in the elements..

A tribander means a rotator meaning a rotator loop in the coax.  A run 
of  8X has relatively low loss at HF and is very flexible. Moreso than 
any of the larger coax cables.  BuryFlex makes for good rotator loops in 
the larger cables

Grounding.  Read the Polyphaser pages.  You might have to search for the 
papers on grounding.
Starting off, you need a "single point ground where the cables (coax, 
rotator, and any control cables) at the point of entry, All grounds tie 
to this including equipment grounds..  Ground "system"! You will need 
more than one rod at the tower and one at the entrance.  Ground the coax 
shields to the tower at both the top and bottom of the tower. There 
should be one ground rod out out say 6 feet from each tower leg with 
grounding cable run our in a radial fashion. Ground rods are spaced 
twice their length.  2" wide copper strap would be preferable, but 
large, bare copper cable will work.  Where copper is concerned, it gets 
expensive quick.
The idea is a grid of grounding wire and rods.  Copper plated rods are 
for protection from corrosion, not conductivity.  Typically Galvanized 
rods are a good bet. The wire, or strap should be CadWelded to the 
ground rods.

Don't forget to run a ground from the tower system to the Single Point 
Ground.
Usually the ground system is limited by space, soil conditions, and budget.
It can be added to as time and budget permit, but copper that's been in 
the dirt for a while requires a good cleaning before Cad welding on 
extensions.

  73 es good luck,

Roger (K8RI)



On 5/9/2016 Monday 5:22 PM, Timothy A. Holmes wrote:
> HI Guys:
>
> Heres another question for the pile as I am beginning my project of 
> rebuilding my tower.
>
> As I purchase new feedline for the project, What kind should I get 
> RG????, LMR???? Etc
>
> Heres the setup:
>
> Radio - Icom 706MKIIG barefoot
> Antennas - 3 element tribander (cant remember the model name but its a 
> real one)
>     - 9 Element horizontally polarized 2m beam
>     - 3 Element 6 meter beam
>     - Some previously un determined 44 beam (what I can find 
> inexpensively as I dont use 440 much at all)
>     - 2 / 440 vertical on a side arm mount
>
> The run from the pass through in the shack window to the top of the 
> tower will be 100' or close enough not to matter.  Price is somewhat 
> of a concern, but I am looking for quality.  As previously noted, I am 
> close to DXEngineering, and for simplicity sake would like to use 
> their products
>
> Thanks
> TIM
> W8TAH
> _______________________________________________
>
>
>
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-- 

73

Roger (K8RI)


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