[TowerTalk] Sealing cables at PVC exit?

[ersmar at comcast.net]

Ed et al:

<Big snips throughout below>.

73 de
Gene Smar  AD3F


 -------------- Original message ----------------------
From: "K8RI on Tower talk" <k8ri-tower at charter.net>
> 
> 
> 
> > Ed:
> >
> >     My first suggestion to you:  Use 4 inch conduit if possible.  I used 
> > three inch because that was the max width hole my DitchWitch (tm) would 
> > cut for me.  I should have at least tried to sink 4 inch PVC into the 
> > hole, but too late now.
> 
> Unless running large coax and lots of them you will probably find the 3" to 
> be sufficient.  I used 3" with 5 runs of LMR400, 4 of RG-6, large rotator 
> control cable, and the control cable to the remote coax switch.
> 


I guess the size of the conduit depends on how many right-angle pulls you go through, in addition to the number of cables.  Most folks in the bidness (outside plant construction) recommend no more than four 90's in any conduit run, to minimize the crushing force applied to the cables under tension in the conduits during pulling.  In my case, the conduit system is only fifty feet from the shack, but it includes three 90's (in three dimensions) and one 45.  And that's after I remove the non-glued elbows at the tower's steel box.  Still wish I had gone to four inch PVC, though.


> >
> >     Finally, you ought to drill a few half-inch diameter holes in the 
> > undersides of the low spots in your PVC
> 
> I think you will find that 1/8" will be plenty and unlike the 1/2", sand 
> will not tend to work up into the conduit and if they find them, mice fit 
> easily through 1/2" holes.  



I think I decided on the larger hole size so that I could ream out the inside of the opening a bit to remove the bits of sharp plastic left after drilling.  If you drill small holes, they'll also have these sharp edges, but you won't be able to remove them, depending on where they are in the PVC (near the end vs in the middle).  I was concerned that I might snag the coax or control cable jackets on this sharp stuff and effectively breach the insulation.  The landscape material is supposed to keep out the critters from these holes, while allowing accumulated water to drain.



>Unless in clay or very heavy loam 


....That's what I have here in the DC area.



> 
> 
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
> >
> >