[TowerTalk] Underground conduit question

Tue Feb 8 17:58:00 PST 2011

I've seen countless posts in various forums regarding the perforation of perfectly watertight pipe to aid "drainage".  Do people get that much airflow through their buried and sealed pipe that condensation is a major problem?

I can tell you that where I live in upstate NY, if you bury perforated pipe below the frost line or, for that matter, more than a couple of feet deep, it will fill with water and stay that way forever.  I'm no expert, but I kinda think that's worse than some condensation!

Al
AB2ZY

-----Original Message-----
From: towertalk-bounces at contesting.com [mailto:towertalk-bounces at contesting.com] On Behalf Of Daryll Webb
Sent: Tuesday, February 08, 2011 1:27 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Underground conduit question

Howdy   I like this group!  Good stuff all around.
Hr is what I plan to do with my install.
As the feed line will be direct bury, not submersible! I plan to use the plastic pipe that is used for leach beads, it has drain holes in it.
That way if any water gets into it I think it will drain as it is suppose to. A thin layer of sand or pea gravel should make it work.
It will only need to be 12" deep or less jest to keep it from coming up after a few years.
If I need to change cable I hope to hook the new one to the old one and pull it in as the old is pulled out.
In theory it should work. Wish me luck  Daryll kg9nd

________________________________
From: Peter Dougherty <w2irt at verizon.net>
To: towertalk at contesting.com
Sent: Tue, February 8, 2011 12:10:14 PM
Subject: Re: [TowerTalk] Underground conduit question

On 2/7/2011 1:55 PM, Peter Dougherty wrote:
> Hi all,
> Several years ago I had a run of 4" solid white PVC tubing run on a
downward

Very important...How long is this run and how deep.
It's roughly 41 or 42' long, buried about 18" down at the deep end and 12"
on the shallow end. It was installed when an electrician put in a 120 VAC outlet for our nearby pond. These three pictures can describe it better than my words can:
http://s291.photobucket.com/albums/ll290/W2IRT/Towers%20and%20Antennas/

Snow won't hurt, it's just a nuisance.

>>IF the conduit maintains a grade all the way it won't fill up with 
>>water and freeze. This part I'm afraid to ask. What did you use to 
>>block the end
in the
>>yard to prevent "critters" from turning it into a ready made home?

I used 1/2" wire-mesh (hardware cloth) fastened by a hose clamp. The cables run through the squares.

> After the lines emerge from the conduit they just run over top of the
ground
> to their respective antennae. After a coax failure to my loop, I tried 
> pushing a fish-tape through the conduit in hopes of running a new 
> length
of
> cable but it became obvious that the inside of this conduit had gotten 
> ice or muck inside, so I need to wait until spring to try and remedy things.

>> If there are more than a few cables in the conduit and/or it's a long 
>> run it'll be very difficult to push a fish tape through it once it 
>> has cables in place.

If you look at the pictures referenced above, I have a number of cables that exit the house and then go up to the vertical section just a few feet away (which now has a 180-degree cap on it) and to an antenna switch box mounted on the side of the tower. One line (the 160 antenna) comes back down that riser and along the full length of the conduit. I have 3 or 4 other cables that run the full length of that conduit (the failed K9AY coax, the control line and a run of RG-6 for a noise sense antenna, which has just now been repurposed as the K9AY coax).

> This now leads to a few much broader questions.
> 1) Can I do anything to improve the drainage of the existing 4" 
> conduit (remember, it's already on a downward angle)? Digging up the 
> back yard is NOT an option.
How deep is it. With cables in the answer is probably not. If the conduit is "always" on a grade with no low spots it should not need any more drainage.

I'm *pretty sure* it's on a constant albeit shallow angle down away from the house.

>> You could build a box for the cables to exit into at the end of the 
>> conduit.  Put some plastic mesh in it along with a few mothballs to 
>> discourage critters.

I think this is the way I'll go, similar to what our sprinkler-system installers did for their junction boxes and valves, etc.

> 2) The coax/control-cables lying on the ground will need to be buried.
Do you mean the ones coming out of the current conduit?

Yes, the lines to the K9AY loop specifically, although I'd like to bury the 160 TX antenna feedline as well. It, however, traverses a lot of very inaccessible terrain (behind rocks, beside an embankment, through a narrow gap between the garage and a concrete fixture, etc, making that job far more difficult. That ground rises and falls considerably, too.

>> Have you considered "direct bury" cables?  Or something rugged like 
>> Davis BuryFlex(TM) and just leave it on the surface or buried shallow?

I guess this is the way to go for the 160 TX, and maybe for the K9AY. I'm using direct-bury sprinkler control cable for the K9AY directionality control and remote power so no worries there. I'm not really a fan of direct-bury, though, since if there is a failure I'd rather just pull a new run in minutes rather than either a) dig out the old one or b) dig a new trench for the new one. I'm definitely interested in a conduit solution.

[pjd] -pjd

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