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Author Topic: Getting coax cable thru conduit  (Read 14029 times)
N4NYY
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Posts: 4821




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« Reply #15 on: September 03, 2012, 06:24:01 PM »


Quote
This is really, really bad advice. You'd be just as well off direct burying the cable. If you've dealt with underground conduit at all you'll know that if there are holes or the sections joints aren't sealed, water WILL get in it. LOTS of water if your soil holds it at all - like putting a sponge in a bucket of water.

Spare me. I did this in 2005. This year, I replaced my 5BTV with a trap dipole, and used the same coax in the conduit I mention. I used Bury-Flex. Not a drop of water or a hint of an SWR problem.

In case you want to count, that is 6 years of a buried conduit that did not have a drop of water in it, because I allowed a path for drainage.
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K8AXW
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« Reply #16 on: September 03, 2012, 09:12:24 PM »

SMI:  I too felt the same way when I installed my PVC pipe underground and pulled several cables through it.

Then one day I accidentally found the PVC pipe had a great deal of water in it at the lower end.  I KNOW that I sealed each joint well and that one end was in an enclosure.  I examined the other end which had a 180° "drip" loop in it and the end sealed with duct seal.  No way water could get in there.

I concluded that the coax heating the air inside the pipe which was buried in the cool earth was condensing and filling the pipe.

I had to drill a drain hole in the last 90° sweep where it came out of the ground at the tower.  So I don't think NYY was incorrect especially since he had a natural slope in his installation.  Even if it was flat, whatever might seep in will eventually seep out.
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AC5UP
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« Reply #17 on: September 03, 2012, 09:46:34 PM »

Every day the conduit goes through a day / night thermal cycle and if one end is higher than the other there will be some natural convection... Like a two story house creates a draft as cool air is drawn in at the first floor, picks up some heat, then rises to exit from the second floor. Unless you live in the desert southwest or a silica gel mine there will eventually be some water condensation inside the conduit.

A drain hole at the lowest point(s) of the conduit run is a good idea. Considering the original post mentioned 85' as the length of the run I don't see this as a major engineering challenge, but I remind myself there is no issue so complex or difficult to understand that it cannot be resolved by the proper application of high explosives.
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K8AXW
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« Reply #18 on: September 04, 2012, 09:08:36 AM »

Quote
I remind myself there is no issue so complex or difficult to understand that it cannot be resolved by the proper application of high explosives

YES!  An this is exactly why I have a very nice .44 Magnum!  It's good for everything from problem solving to frustration to migraines!
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N4NYY
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« Reply #19 on: September 04, 2012, 09:12:03 AM »

Quote
I had to drill a drain hole in the last 90° sweep where it came out of the ground at the tower.  So I don't think NYY was incorrect especially since he had a natural slope in his installation.  Even if it was flat, whatever might seep in will eventually seep out.

Thanks. Even it is was flat, or the slope was to the house, instead of away, I would still drill holes. The thing is water will always find a low point and drain. Unless, you seal of its exit.

My conduit is only about 3" deep, just below the grass root line. If you wanted to really be anal about drainage, you can dig a little deeper and fill below the conduit, about 3" of 3/8" stone.

But that other guy was out of line for calling me on my bad advice, because he has no knowledge of my installation of my conduits.
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AC5UP
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« Reply #20 on: September 04, 2012, 01:09:02 PM »

But that other guy was out of line for calling me on my bad advice, because he has no knowledge of my installation of my conduits.

/soapbox=on

Pet Peeve of mine:  Lets say I post a question. I'm restoring a frenulum and want to re-paint the gnat catcher housing but can't find a match for the original color. Wondering what color I should consider.

First respondent says to choose a good high-visibility yellow as that will make it more obvious when the gnat catcher needs to be cleaned.

Second respondent says a nice hammertone green is not only a good color match for the internal hinchel coupling, but will add value should I try selling the frenulum at a swapmeet in New Jersey.

Third respondent says the first two are both bad ideas, but offers no suggestion of something better.

The third respondent will be promoted to my ignore list because they've added nothing but noise to the thread.

/soapbox=off
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N4NYY
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« Reply #21 on: September 04, 2012, 01:11:37 PM »

Quote
Second respondent says a nice hammertone green is not only a good color match for the internal hinchel coupling, but will add value should I try selling the frenulum at a swapmeet in New Jersey.

That is a low blow! LOL.

Should I try to sell it at our hamfest?
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AC5UP
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« Reply #22 on: September 04, 2012, 01:24:12 PM »

...I have too much respect for my frenulum to even consider sending it to New Jersey.

Besides, when it comes to the craptastic September 16th Hamfest mentioned here:  http://www.eham.net/ehamforum/smf/index.php/topic,84791.0.html  I am firm on this --- No Lt. Uhura, no AC5UP!

And that's my final offer.   Tongue
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K3GM
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« Reply #23 on: September 05, 2012, 06:58:11 AM »

I need to run 85' of coax (213) thru conduit. There is already one electrical cord in the conduit. I seem to be getting stuck on every connection joint. Any ideas how to do it more effectively than I am at present?

I'm a big proponent of pulling one "cable" at a time, be it coax, or a control cable.  Doing so prevents the bundle from twisting around one another as it gently corkscrews down the pipe, and allows easy removal of an individual cable if necessary.  My electrical apprentice kid showed me this trick years ago, and I use it all the time.  I leave no pull lines for future use in my 160' run of 3" grey PVC condiut.  Rather I shoot a "ghost" down the pipe for each new run.  The ghost is very rudimentary and is not a commercial one like my son uses in his business.  It's merely a plastic grocery bag scruntched up and stuffed lightly in the the pipe with a mason's line tied to it.  I prefer to send the ghost down the condiut using the exhaust of a shop vac, but you can suck it down the pipe as well.  Either way, the thing goes down the pipe so fast that the line will burn your fingers if you're not careful.  Once the ghost flies out the other end, I proceed to pull the new line; no twists=no dragging.  Each line is a straight pull.  

Do thoroughly glue your pipe joints, and don't push the cables into the new piece of pipe and then attempt to glue the joint together. Use 90 degree "sweeps" instead of elbows.  The turn is more gradual.

Allow for drainage in your run of conduit.  The pipe breathes in and out, sucking in damp air which condenses on the cool interior of the pipe.  With time, it will literally flood the low spot of your run.  Add a tee in low spots to allow the water to drain into a small pit filled with gravel or loose rocks.  FInally, I stuff each end of the pipe with coarse stainless steel wool to prevent "wildlife" from building a home inside it.  Rodents hate steel wool, and SS wool will last forever.
« Last Edit: September 05, 2012, 07:58:41 AM by K3GM » Logged
K0JEG
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Posts: 679




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« Reply #24 on: September 05, 2012, 04:29:04 PM »

If you really want to futureproof your installation, take a look at pulling in interduct:

http://www.americantechsupply.com/innerduct.htm

http://www.americantechsupply.com/maxcell.htm

However, the stuff's not cheap and if you don't put in pull strings/lines when installed it will be difficult to use later. I've seen the maxcell stuff at cable trade shows and it looks like it would work very well.

Seal up the pipe. If water gets in, so will mud, rocks, mice, and just about anything else in the ground. If joints aren't glued they will open up as the ground settles. Most new installations of TV cable use 2" schedule 40 on continuous rolls to avoid having underground splices and couplers.
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W9GB
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« Reply #25 on: September 05, 2012, 05:45:30 PM »

Quote from: K0JEG
If you really want to futureproof your installation, take a look at pulling in Interduct ...
20 years ago, when pulling Multi-mode and Single-mode fiber-optic cables, we placed them inside Interduct that was inside 4" conduit runs.  Interduct was more expensive in early 1990s, but when protecting backbone LAN / WAN connections for health-care/hospital ... the price was small for the future protection.

I noted 5 years ago that AT&T exclusively used direct bury Interduct for their U-verse fiber optic build-out .... using traditional metal or PVC conduit for the 90 degree sweep to the neighborhood pedestal boxes (interconnect access, drops).
« Last Edit: September 05, 2012, 05:52:17 PM by W9GB » Logged
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