[TowerTalk] Direct Burial Of Coax (Was "A Dumb Question")

[Jim Thomson]

Date: Mon, 28 Aug 2017 08:41:34 -0400
From: Dick's <rcblumen at centurylink.net>
To: Tom Hellem <tom.hellem at gmail.com>
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Direct Burial Of Coax (Was "A Dumb Question")


<I stand corrected. I think you folks are correct. My idea of burying coax in sand and protecting it with plastic trim boards is not as good as laying the coax in perforated pvc pipes that have drain holes over pea gravel. Both are as effective in the short run, but <with the pipe you can always replace the coax or add another line if you pre-ran a string or rope with the coax.

<Dick, K0CAT

##  The issue with the PVC pipe  with the aprx .375 holes down each side is..... for ham use, you have to orient the holes, so they are facing up..and down.   In normal drain tile usage, the holes are oriented  so they are on each side, to allow water in..and drain away.     For ham use, with holes at the top and bottom of the pvc.... sure if water gets in, it will drain though the bottom holes, but it will also allow water to ingress,  via the top holes.    A better method would be to use pvc with no holes at all, then  drill out
a single row of holes...and orient those holes, so they face straight down, towards the bottom.    Then at least you get to decide how many holes you want, and what spacing you want, and hole diam.    Then dig your trench, fill partly with sand, put the pvc pipe in, then cover up with more sand, or what ever you want.   You could always add  an above ground T or  Y....and also plug the hole + cables with duct seal at one end.... and leave the far end open.   Then stuff either compressed air or the blow end of  a shop vac at the T or Y.    Then leave it on for 40-60 mins.   You would dry it out pretty quickly.   I have a unit that is made to dry out wet vehicles.    Stupid high pressure vs a shop vac..and has heat too.   Bought it at the local harly davidson dealer.  Called an  Airforce blaster.. made in NY...and built like a tank.   You could also put a nitrogen bottle on one end, the humidity  is 0 % with nitrogen. 

##  Cables sitting in water, have to be designed to sit in water  27 /7.   Once water gets into the pvc, it stays put.... and just accumulates, gets worse.    If the pvc is only less than  1 foot below ground, the standing water inside the pvc will  freeze in winter, compounding issues.   Folks who have in ground sprinkler systems  know this..which is why in the winter, they are shut down for the season, and standing water is blown out with compressed air. 

##  Drilling out a single row of holes by hand, imo, has a lot going for it, then sit the pvc in sand filled trough, then cover it up with what ever you want.  Any water just drains into the sand below.  Cables are not sitting in standing water.  The shop vac procedure can be done once per year during the hot summer months, with far end opened off, to  completely dry it out....which may nor be required at all... but easy to do. 

Jim   VE7RF