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[TowerTalk] Underground cabling

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Subject: [TowerTalk] Underground cabling
From: (Robin E. Midgett)
Date: Fri, 03 Dec 1999 20:34:47 -0600
Hello Bob & TT,
I did a very similar thing to my shack. My tower is 150' from the house, 
standing in the back yard with very few obstructions between the house & 
tower. I rented a ditch digging machine, laid open an 8" wide ditch from 
the house to the tower base & installed 6" PVC pipe. This PVC became the 
conduit for all my shack <-> tower lines. I also put a 6 AWG bare solid 
copper wire in the ditch (not in the pipe) to tie the tower ground system & 
the house ground together, with 8' ground rods distributed along the way on 
16' centers. BTW, get a ditch digger that you ride on; then you get to use 
the push-blade on the front of the machine to back fill the ditch with. My 
ditch is 18" deep.

The shack end of the pipe dumps out under the house in the crawl space. I 
punched a hole through one block in the foundation below grade for this 
purpose, ran the pipe through, then back filled over the pipe & hole in the 
foundation. After 2-3 years, you couldn't look at the spot & know I'd dug a 
hole there.

At the tower, I simply started angling the pipe up toward the surface of 
the ground about 10-12 feet away from the base & cut the length where I 
wanted it. The feedlines exit the pipe just as it breaks ground within 8" 
of the tower base, & up they go. This made for a very nice straight shot 
through the pipe to the house with the pull line, which is a 1/4" Nylon 
rope, twice the length of the pipe. The slack in the rope stays coiled up 
under the house. I used a shop vac to pull a 6" styro-foam ball (sanded 
down slightly) & very light string through the pipe initially, then 
used  the light string to pull in the permanent pull rope.

The tower end of the pipe is also the source of my water problem. I haven't 
taken the trouble to effectively water proof the tower end of the open 
pipe, so it acts as a collection point. It never has drained under the 
house, & I have pumped it out once or twice, but it isn't a priority. I 
could have installed a couple of 90 degree elbows, but that would have been 
a pain because I use 1/2" & 3/4" CATV hard line for my feeds. Getting those 
feedlines through that maze would be a pain. Probably the best I could do 
is to wrap the lines up to the pipe opening with rubber sheet & seal with 
hose clamps; this "hood" would keep the majority of the water out.

One thing I'd do differently if doing it over, I would put perforated 
sections of pipe in the line at the lowest points in the ditch to allow 
water to drain out. As it worked out, both ends are higher than the middle, 
so I get water accumulation in the middle. If you choose this option, I 
suggest putting a layer of 1-1.5" rock in the bottom of the ditch where the 
perforated sections go to allow any water to drain through to the earth.

My source for the PVC is my neighbor's scrap yard. He has (present tense) 
hundreds of 7-8' sections of the stuff, most with a swagged  end, so I 
didn't need any couplers. One issue, though is that this is thin wall pipe 
(1/16" or so), regular PVC fittings a the plumbing store don't fit it well. 
I got "whatever quantity" I needed to do the job for $75.00. I could have 
made my own perforated pieces, had I wanted to by using a 1" paddle bit to 
perforate a section or two.

My lawn tractor makes a FINE cable pulling tool through this pipe. I have a 
small hole in the front of the house above grade in line with the tower 
conduit. This small hole is lined with a stub of 1/2" PVC to prevent 
abrasion on the pull rope. I simply pass the end of the pull line through 
the small hole in the front of the house & hook it to the tractor when I 
need to make a pull. My wife eventually got over the number of holes I have 
punched into this our first home!

If I may be of any help, please feel free to contact me. This was a bigger 
job than I first anticipated; but then most of them are!

At 09:56 AM 12/3/1999 -0500, Robert D. Crossland wrote:

>Hello to all,
>It appears my dream is finally coming true, that is owning a home where
>I can install a tower.
>While I think, re-think and think again about the type of tower, antenna
>etc I'll be using, one area comes to mind that I am in real need of
>advice in, and that is the best way to run coax and control line(s) to
>the tower.  Here are some high level details.
>- The tower will be placed about 210 feet from the shack.
>- Tower will be 55 foot crank-up.
>- Antenna will be a tri-bander of some flavor.
>- Have unobstructed access between tower and shack, thus can dig ditch
>between the two.
>I'd look forward to hearing your ideas on the best approach to running
>these cables underground?
>PVC with drain holes for moisture escape?
>No drain holes?
>How deep to dig ditch?
>etc, etc, etc
>I read some of the archived threads on this topic but they were a bit
>dated and technology may have improved since then (1997-1998), I really
>don't know.
>Any and all advice will be greatly appreciated folks.
>Thanks in advance for your input.
>Take care
>Bob, N3IXR
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Robin E. Midgett KB4IDC EM66se
1/2 of the Award Winning NT4L Rover Team

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