[TowerTalk] Overhead cables from tower to shack

[Gene Smar]

Hans:

I agree with John G4ZTR: Don't just hang a messenger wire (what your steel wire is called) onto your tower and load it with coax and control cables without considering the sideways force this will impart on your tower, guyed or otherwise. It's best to go with your on-ground alternative. If you can thread the cables through a PVC conduit, even a conduit lying on top of the ditch, you get even more mechanical protection for your cables. 


73 de
Gene Smar AD3F

On 09/21/12, John Lemay<john at carltonhouse.eclipse.co.uk> wrote:

Hans



I don't feel competent to comment about lightning strikes and earthing, but
your proposal has some engineering issues:



The catenary of wire plus control cable plus coaxial cable will be heavy and
will exert a sideways pull on your mast. Under windy conditions the pull
could increase and vary. Are you sure your tower can cope with the extra
load ?



John G4ZTR





_____ 

From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Hans
Hammarquist
Sent: 21 September 2012 13:59
To: towertalk at contesting.com
Subject: [TowerTalk] Overhead cables from tower to shack



To save some (~250 feet) of wires and cables I am thinking of hanging a
steel wire with attached cables (coax and control) between the (near) top of
my tower directly to my radio shack located on the top floor of my house.
Instead I can pull all the cables down the tower, through a ditch i the
ground and up along the side the house up to my shack, with much better
possibilities of good protection from light-strikes.


The tower is well grounded (as far as I know, 9 grounding rods, Ufer ground
and whatever else) The house has a Faraday grounding cage with a total of 6
grounding spots (plus whatever it gets through the utility connections). The
lightning protect has been tested (by direct lightning strikes) at least
twice. Burn-marks to prove it.


I am planning to let the coax cables be grounded in the tower through a
plate equipped with bulkhead connectors and ground them at the house with a
similar plate - bulkhead connectors. That plate will be directly connected
to the lightning protection next to my shack. There are 4, thick, copper
wires that connects the lightning rods over my shack to the grounding rods
four stories down.


What I am afraid of is, in case of a lightning strike (direct hit or
near-by), the big open loop created by my overhead wires together with the
tower, the lightning protection of the house and the ground will induce
enough current to cause damages. This loop will have an about 70 x 125 feet
opening, enough to make it a good loop antenna (not the purpose though). (No
I don't have any AM stations around that will have their radiation pattern
altered.)


Anyone with experience from this, or any objections? I would not like to
find my installation looking like a fried chicken after inclined weather.


73 de,


Hans - N2JFS
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