[TowerTalk] Coax grounding to crank-up tower for shunt-fed antenna

[James C. Hall MD]

Richard W. Harris wrote:

>Hi,
>I'm working on a shunt-fed tower for 160M.  I'm routing the coax inside
>the center of my crank-up tower.  Do I need to ground the coax shield to
>the tower at the top and bottom of the tower?  I recall reading that I
>should perform this grounding of the coax shield and another place I
>read says not to worry.  Just wondering what the group has to say about
>this.  How about the rotor control cable?  Do I need to do anything
>special with this cable other than make sure it is inside the center of
>the tower?
>
>Also, ON4UN's book says to tape/tie the coax to the inside of the tower
>leg.  Easy to do on a fixed tower but a crank-up won't allow this (at
>least if you want to be able to crank the tower down).  Any suggestions
>here on what to do with the coax going up through the center of the
>tower to the yagi antenna on the top of the tower?  I was thinking that
>I could use a grounding kit and ground the coax shield at the top and
>bottom of the tower but would need to let it hang in the center to allow
>me to crank the tower down.  Any problems with coax weight stretching
>the cable?  Tower is 4-section 72 foot crank-up.
>Thanks
>Richard Harris - KJ7CU
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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>
Hi Richard:

I have a UST 572 crank-up tower and I use the stand-off coax arms. I use 
Polyphaser ground kits to ground the coax cables to the top plate and a 
fabricated aluminum plate at the base where I use copper strapping to 
attach to the coax cables via a long barrel connector (bulkhead 
connector). The coax arms actually allow a 3/4" square aluminum channel 
(bought on eBay for cheap) to fit and extend out the other side of the 
tower. I just drilled and bolted this arm and dropped a wire which is 
held taught by a 2 x 4" clamped to the bottom of the tower. Then just 
connect up your capacitor(s) and tune it up. Works great !

73, Jamie
WB4YDL