[TowerTalk] Underground conduit question

[Rroger (K8RI on TowerTalk)]

On 2/8/2011 12:10 PM, Peter Dougherty wrote:
> 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/
Looks like a neat installation.
A couple of things to try.

Remove the grid from the far end.  With some one on both ends, can you 
move that piece of coax, or any of the cables in the conduit. If you can 
move the bad piece you have a ready made messenger cable.   Tie/tape a 
piece of 1/4 to 3/8" nylon or Dacron rope to the failed piece of coax 
and pull it into the conduit by pulling the bad piece out the other end.

Alternatively:  There should be some play in the cable, not much but 
maybe a 1/2" to 1".
When you slide the fish tape in, I assume you are going in from the 
basement end.  When the tap stops going in, does it get steadily more 
difficult, or does it stop abruptly? If it get more difficult as it goes 
in which it should, you might try having someone take hold of the cables 
at the far end while easing the tape in. When the going gets tough move 
the cables back and fourth that inch or so while maintaining pressure on 
the tape. Conversely you can move the tape back and fourth with the 
cables, but add extra force to the tape when the cables move forward.

Often the cables get wrapped around each other forming a spot that will 
catch or restrict the movement of the fish tape. there may be a low spot 
where water has collected and frozen but it should not fill the entire 
conduit. It may OTOH guide the end of the fish tape into a "blind end", 
or trap it where cables are caught in the ice.

There are several types of fish tape ends. The one I have is like a 
bullet with a slot cut in it  and it rotates. The more common kind have 
the end bent back to form a kind of clip.  Some times I start wrapping 
the end with tape to form a double taper, then grease it up "liberally" 
with that well known "wire soap" or "wire pulling soap" I may have 
mentioned.

IF OTOH the fish tape stops abruptly, note how far in the conduit its 
gone.   Try rotating the tape and you move it back and fourth about an 
inch or two. That would indicate it had caught on something or caught at 
the junction of some cables and ice.  Try coming in from the other end. 
If it stops again note how far in it's gone.  The two measurements 
should give you and idea as to how long an area is stopped up and 
possibly where you *might* have some ice, a nest, or tangle of cables.

IF you suspect ice, borrow a hair dryer and blow warm air though the 
conduit for several hours.  Be really careful about temperature.   That 
is why I didn't recommend a heat gun. One is OK, but keep the temp at 
120 degrees or lower.  You might have to plug off the stub going to the 
tower by stuffing a towel or making a foam plug.

IF you can not move the cable, nor get air through the conduit, it 
either has a nest in it or it's plugged with ice. and you may have to 
wait for warm weather.

If you can pull the one cable out, inspect it thoroughly. If you find 
indications of chewing on it, or indications there may be a nest in 
there, it'd be a good idea to pull out all the cables for inspection. I 
had never had rodent's chewing on the cables in nearly 50 years from 
various locations, *until* last winter.  They chewed through two RG-6 
cables that go to the satellite dish.  Those cables were exposed from 
the box on the tower down to the grounding block (which is still about a 
foot above the ground)  They chewed through about half way between the 
box and grounding block which was actually a bit under the snow.
> 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.
I'd suggest a finer mesh. If you can get RG8 through, mice can get 
through.  They can get through unbelievably small spaces.  I've seen 
them disappear through tiny openings as my big cat was closing in<:-))


73 and good luck,

Roger (K8RI)