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[TowerTalk] Routing coax across roof (long)

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Subject: [TowerTalk] Routing coax across roof (long)
From: (Pete Goudreau)
Date: Thu, 14 Feb 2002 22:25:50 -0600 wrote:

> Pete, running coax on a shingle roof is almost a guarantee of a very
> short life (for the coax). The jacket of most coaxes will not stand
> the abrasion of the grit on the shingles.

Good point, hadn't thought about that, was more worried about the 
roof.  But you're right, the coax would be damaged long before the 
roof will be.

> Further, the heat of the sun
> at the roof surface will, even in temperate climates, exceed the 80
> deg. C at which both the jacket and the dielectric will rapidly
> degrade. The center conductor will even migrate over time (in less
> than a week in AZ!).

I believe it, and another good point.  Wouldn't take much longer here 
in the Dallas area either, I suspect.  That's another reason to use 
sleepers or the like.  Now I'm more seriously considering stringing 
the coax along a catenary.  Ah, the fun of statics and material 

> The PE jacket of Buryflex will stand more
> abrasion than PVC jackets, but not well enough for direct contact 
> a roof. Ideally, you should either route under the eaves or through
> the roof via a weather protected vent. If a short run ON the roof is
> necessary, the coax should be on a runner of wood, approx 3/4 X
> 1-1/2", painted to match the roof. This will be much cooler than the
> immediate surface. Painting the coax with an alkyd brilliant white
> will also help with sun protection. Good luck with the project! 73,

Thanks for the tips, very valuable, hadn't thought of painting the 
coax, nice trick.

Not sure how to anchor the sleepers though, would you use roofing 
nails or the like and simply seal up the mess with some roofing 
caulk?  Would have to be quick and easy to do...before the wife 
caught on to me nailing stuff to the roof...<g>

Yep, an ariel plant is looking much better all the time.

Thanks again,
Pete, AD5HD

> On Wed, 13 Feb 2002 22:34:48 -0600 Pete Goudreau <>
> writes:

>> A question to the list.

>> From a planned antenna installation on a chimney, coax (BuryFlex)
>> needs to be routed roughly 10' along the adjacent sloping roof
>> surface to a ridge where it needs to run about 20' to the gable 

>> where it can run down an unrelated fiberglass mast and then to the
>> ground along with a couple of other feedlines.

>> The problem I'm trying to find a simple solution to is one of
>> protecting the shingles from damage as a free coax run would cause 

>> working back and forth across the shingles in the wind over time.

>> Anchoring the coax seems to be a good solution but with what? And 
>> to do it so the wind won't lift the whole line and damage the
>> shingles or cause a leak?

>> An alternative seems to be to rig sleepers over and along the ridge

>> so that they don't have to be anchored but how to keep the whole
>> thing from lifting in the wind and causing damage anyway? And what

>> would they be made of? Commercial sleepers are PVC but meant to lie

>> flat on a flat roof, not sure it'd be a good choice in this
>> application.

>> Thought about running a cable directly from the lower chimney mount

>> to the fiberglass mast (pretty much a level run) and having it
>> support the feedline, as a catenary, but the tension required is in

>> the hundreds of pound range for a sag of a foot or more. Not sure I

>> want to subject the chimney to any more loading than is necessary 
>> it's a bit of a side load on the fiberglass mast, too.

>> So, I'm pretty much out of options. Is there some commonly 
>> roofing item that makes this an easy thing to do or is there some
>> other way to do this that I'm missing?

>> Running in to the attic space is not an option, I think, as 
there's a
>> gas line for the furnace there and lightning wouldn't be a good
>> thing.

>> This feedline, and the others it meets up with at the fiberglass
>> mast, are to be grounded via Times ground kits, through a Harger 
>> clamp, to a copper clad ground rod where they come to the ground 

>> are then buried around to the master ground bar at the service
>> entrance. This ground rod is part of a lightning ground field as
>> well.

>> Any suggestions, thoughts, pointers, etc., are greatly appreciated.

>> Thanks, Pete Goudreau, AD5HD

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