[TowerTalk] SUMMARY: Buried Hardline

[Setzler James M NPRI]

Thanks for all of the responses.  The consensus is to protect the bare
aluminum in some way.  The most obvious is in pipe of some sort.  I started
tilling the trench across the yard last night. 

A tip o' the hat to K6LL, N4ZR, K1WCC, K1ZAT, K1BV, K5UO, K1TTT, VE3AD,
K8DX, W1JCC, K2WK, K1VR, AK9F, N1RL, and N2MG.

73  James / k1sd
Rhode Island
   
>>  setzlerjm@code80.npt.nuwc.navy.mil <<

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Question:

I'm going to bury some 3/4" CATV bare aluminum jacketed hardline across the
backyard. Do I need to encase it in plastic pipe or can it be buried
directly?  Will this stuff deteriorate if left in direct contact with the
soil?

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What I did was go to my local Lowe's (a home owners paradise) and buy
two 100 foot roll of corrugated four inch flex drain pipe (without the
drain holes).  this is the stuff that home builders run from rain down
spouts into the back yard someplace, black in color.  Dug a trench
maybe six-seven inches down, laid two runs of flex drain pipe into the
trench, and back filled.  Then ran the CATV's thru it to the shack.

After I ran all the CATV's I wanted, I visited my local tire shop
looking for a rubber inner tube, they had one with a hole about the size
of quarter they gave me.  Cut pieces out of it about a foot long, split
it at the seam and then wrapped it around the ends of the flex pipes and
CATV's securing with heavy duty tie wraps.  That was to keep critters
and water out of the duct.

A 100 foot roll of flex drain pipe cost about $15.  A 100 feet of PVC,
couplings, elbows, etc could easy run up to 50-75 bucks.  the flex is
easy to manage.  While most CATV is made for direct bury, the duct will
give you the option to add or subtract at will.

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I laid on the surface of the ground a 150 foot run in 1978 when we moved
back
to CT from RI.  When I moved to NH in 1992, I rolled it up only to find that
it
had many cracks and a deteriorated surface which I attribute to the acidic
oak
leaves and pine needles which covered it.

I'd suggest plastic pipe.

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I would still put the coax into some sort of 'protective' pipe, e.g., PVC to
protect the covering (from experience) from:

1. Upheaval of rocks during winter. They can cut the covering.
2. Future digging you or a service company may make in the future, e.g. new
cable TV / telephone/power burial by a sub-contractor who is in a hurry and
shows up a day before promised and buries his TV cable where HE wants
too.(Cut dusk-dawn cable, Beverage feedline)

Or your mistakes in doing some digging.

Hindsight is 20-20: Plot the burial from nearby markers (trees, fences, etc)
for future reference.

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You will likely have anode action (aluminum is sacrificial to zinc and
copper), so do not bury directly.
Suggest you go to the co-op or farm supply place and get semi-flexible "poly
pipe."  It can change directions gently, which is what you need.

(I have several hundred feet in the ground -  get large od stuff.)

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put it in pipe.  the aluminum in typical acidic soil  with rocks will be
scraped and rot out very quickly.  the stuff they make to bury has not
only a pvc jacket but a goop that seals cuts in the pvc to keep water
away from the aluminum.

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By jacketed., do you mean that it has a insulated covering over the
aluminum? If not I would keep the cable elevated. I am using flooded 3/4"
CATV
hardline here. Flooding the cable means that it has a permanently sticky
material between the aluminum and the UV proof plastic jacket. It can be run
aerially or directly buried. The first 60' of mine is underground, pulled in
6" perforated plastic irrigation tubing ( perforated to allow any build up
of
water to seep away), the rest lays on the ground in the woods. Hope this
helps.

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I can tell you that K3LR went the pipe route and spent a ton of time/ money,
and water still got in it.  For his long runs of CATV he just dug a trench
and
put in and checks it occasionally for loss.  So far so good after about six
years.
He figures when it goes bad he'll just bury some more :-)

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Our acid soils will have an effect if you are close to the surface. the
farther down you go, the better off you'll be. Seems to me K3LR and I had
this discussion abt his set up. I think he used some sort of tar to coat
the hardline and add a layer of protection. 

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I have 2 runs of 3/4" and 2 runs of 1/2" CATV stuff.
About 160' of it goes thru 6" corrugated drainage pipe
and the remainder lays on top of shale.  That section
is where I painted the hardline with whatever paint I
had at hand.  I used a painting glove which made the
job quick, albeit a bit messy.  This was done based on
what I read here.

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Not really. Don't think. But it will crump when struck by a
shovel. I use PVC pipe to protect hardline.

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Bare will eventually rot out, but take quite a few years.  Jacketed will
probably outlast us.

Putting the bare inside PVC may slow the process, but eventually mineral
laden water will get to it and start eroding the outer conductor. 
Again.....takes a Looooong time.

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Aluminum does not hold up very well in contact with most soils. 

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Unless it is marked for "Direct Burial" it probably won't do well in the
dirt.  All DB types I know about definitely have a jacket.  Bare
aluminum is not happy on/in the ground in general (it corrodes with the
chemicals/acids etc.)  Although some folks use aluminum radials for
their verticals, others claim aluminum corrodes too quickly when in
contact with the ground (surely depends on exactly what you have for
dirt!)

I'd go with the plastic pipe (PVC?), if you want to be sure it'll last.

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I suspect so  - my local cable company uses special small-diameter flexible
conduit when they put it in the ground, and our soil isn't that different
from yours.  I have mine just sitting on the surface once it exits the
mowed part of my yard, but in the yard where it's buried it's inside
conduit.

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EOF






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