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Author Topic: RG-213/u: direct burial?  (Read 8611 times)
KC2KMJ
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« on: July 09, 2011, 03:57:26 PM »

I need rougly 90' of coax for my HF antenna install. I've tried to determine if the RG-213/u "MIL-C-17" determines burial but haven't been able to confirm. Is "RG-213/u" direct burial or does it need to directly state this? I was considering Davis 9914F but then found out it's foam dielectric and I've had bad experiences in the past with foam. I can get 213/u (MIL-C-17) locally for a good price but was wondering about direct burial application. Thanks.
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W8JX
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« Reply #1 on: July 09, 2011, 04:51:14 PM »

I have a run that has been buried for 15 years now. It is pretty tuff stuff and as long as it is not rocky soil that could damage cable it will be fine.
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KC2KMJ
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« Reply #2 on: July 09, 2011, 06:05:08 PM »

John, does/did your cable indicate anything about being direct burial?  I've seen 213 with that printed on there and others that don't.
« Last Edit: July 09, 2011, 06:32:01 PM by KC2KMJ » Logged
W8JX
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« Reply #3 on: July 09, 2011, 06:40:48 PM »

Mine is from a roll of new surplus Mil Spec 213 I bought about 20 years ago.(it came from a gov supplier and was real mil spec 213) I still have some around that has never been used and still looked great last time I saw it but I do not have it handy at moment to tell you what it says on it. (I am not in shack either) Sometimes you can find some RG 393 which is a double shielded RG8 type cable with a very tuff jacket and teflon dielectric. Good stuff if you can get your hands on it. The RG 58 version is called RG 142
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K9KJM
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« Reply #4 on: July 10, 2011, 10:00:42 PM »

It is always a very good idea to put any type of coax used inside some type of "conduit" instead of direct bury. For lots of reasons.   The "conduit" does not have to be actual expensive conduit, But any type of cheap low cost plastic pipe.   Corrugated 3 and 4 inch diameter drainage pipe sells in the 20 some dollar range for a 100 foot long roll.
Very cheap insurance. Put a pull string in it right away and you can always pull more coax through in the future if wanted.   Also, While the trench is open, Be SURE to also lay in a bare copper wire or copper tube OUTSIDE the conduit to bond your ground systems together, And to add to your overall ground system.

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K1CJS
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« Reply #5 on: July 11, 2011, 05:17:54 AM »

I would second "KJMs answer.  It is ALWAYS better to do a job once and be done with it.  Putting a cheap conduit in place is wise for more than one reason.  If you want to run more cables or run a rotor control cable one day, you won't have to dig again.  And, if the co-ax developed problems, it is far easier to pull it out to check it than it is to dig it up.

You may have your reasons, but the smarter, easier and far better way to lay underground lines is to put them in a conduit.
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W8JX
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« Reply #6 on: July 11, 2011, 07:42:29 AM »

It is amazing how many can take a simple job of slicing damp ground and pushing in some direct burial 213 and make in complicated. Conduit is not needed here and can bring its own problems. It can fill with water over time and limits routing options as well to name a few. The conduit will cost you more than coax too. (and how much more depends on size of it)

BTW I dug out my old roll of 213 and it says "Times Wire and Cable Company Inc    Mil Type    RG-213/U" on coax.
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K8KAS
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« Reply #7 on: July 11, 2011, 08:24:23 AM »

I used the RG213 on the ground for years with no trouble, but when I put coax a few years ago inside PVC pipe I had water in the PVC and trashed the coax in a year. The pvc was very well sealed at both ends with RTV. The nice thing on the RG213 on the ground it sort of melted into the sand/ground in 6 months and you could not see it. No pipe for me again...Denny K8KAS
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WB2WIK
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« Reply #8 on: July 11, 2011, 09:16:26 AM »

I need rougly 90' of coax for my HF antenna install. I've tried to determine if the RG-213/u "MIL-C-17" determines burial but haven't been able to confirm. Is "RG-213/u" direct burial or does it need to directly state this? I was considering Davis 9914F but then found out it's foam dielectric and I've had bad experiences in the past with foam. I can get 213/u (MIL-C-17) locally for a good price but was wondering about direct burial application. Thanks.

MIL-C-17 is just the general specification for cables.  It doesn't imply anything other than it was manufactured by a Qualified Product List supplier.

"Direct burial" cable is a special design that is self-repairing if pierced.  To do that, during the manufacturing process a tar-like substance bonds the outer jacked to the outer conductor (shield) of the cable, making the cable a bit more difficult to strip and work with.  The stuff is sticky and makes a mess, but it serves a purpose.  If you can install the cable so that it is never pierced by anything (including the sharp teeth of critters outside!), it shouldn't matter if you use "direct burial" cable or not.  I've used regular high-quality RG-213/U buried slightly beneath the soil lots of times, often for several years, with no issues.  The issues I've had are mostly above ground, where rodents can chew on it!
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K1CJS
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« Reply #9 on: July 11, 2011, 09:34:04 AM »

I used the RG213 on the ground for years with no trouble, but when I put coax a few years ago inside PVC pipe I had water in the PVC and trashed the coax in a year. The pvc was very well sealed at both ends with RTV. The nice thing on the RG213 on the ground it sort of melted into the sand/ground in 6 months and you could not see it. No pipe for me again...Denny K8KAS

You didn't put drain holes in the PVC--or use a conduit that had drain holes in it already?  Didn't have any gravel under it either, huh? No wonder you had problems.  If you don't do a conduit installation right, it isn't worth doing at all.  

Another thing--if you live in an area where the ground freezes during the winter, just pushing coax into the ground a couple of inches isn't going to be conducive to making the coax last longer either.  Frozen ground can be just like a knife to coax if something heavy goes over it.  In any event, if you do the job once and do it right, you'll never be sorry.
« Last Edit: July 11, 2011, 09:58:11 AM by K1CJS » Logged
W8JX
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« Reply #10 on: July 11, 2011, 11:21:06 AM »

You didn't put drain holes in the PVC--or use a conduit that had drain holes in it already?  Didn't have any gravel under it either, huh? No wonder you had problems.  If you don't do a conduit installation right, it isn't worth doing at all.  

Over rated and not needed. I have a 175 foot run of 8/3 UF that I just threw in trench with water line going to barn 25 years ago. No conduit, no problems. I regret not throwing some RG 213 in trench too.

Another thing--if you live in an area where the ground freezes during the winter, just pushing coax into the ground a couple of inches isn't going to be conducive to making the coax last longer either.  Frozen ground can be just like a knife to coax if something heavy goes over it.  In any event, if you do the job once and do it right, you'll never be sorry.

Well I live were temps have been as high as a 100 or so (97 right now) and as cold as 28 below and my coax has never failed in ground or in grass. Frozen ground is not going to do squat to cable unless it is maybe real rocky. Some like to make a major project out of a minor one.
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K1CJS
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« Reply #11 on: July 12, 2011, 10:27:52 AM »

....Some like to make a major project out of a minor one.

Touche--but the opposite is true also.  Some like to do a project time after time because of changes or additions, while if you do it right the first time, you'll never have to do it again.

As you also said--

Quote
I have a 175 foot run of 8/3 UF that I just threw in trench with water line going to barn 25 years ago. No conduit, no problems. I regret not throwing some RG 213 in trench too.
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W8JX
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« Reply #12 on: July 12, 2011, 11:03:05 AM »

Touche--but the opposite is true also.  Some like to do a project time after time because of changes or additions, while if you do it right the first time, you'll never have to do it again.

But using conduit does not promise no problems and no rework needed. So doing it right is a matter of point of view at times. Conduit near surface by nature will have frequent temperature swings and pressure changes because of it which will tend to draw moisture that can collect in conduit over time. If you really want to use it it would do better either below frost line or with positive venting to keep moisture out.

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WB2WIK
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« Reply #13 on: July 12, 2011, 02:05:25 PM »

Anecdotally, most of the problems I've had with coax occurred above ground, not below it.

That's because the squirrels and such don't live below ground and some like to snack on coax.

Moles do live below ground and have sharp teeth but haven't given me many problems like the above ground critters have.
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K1CJS
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« Reply #14 on: July 12, 2011, 05:16:54 PM »

But using conduit does not promise no problems and no rework needed. So doing it right is a matter of point of view at times. Conduit near surface by nature will have frequent temperature swings and pressure changes because of it which will tend to draw moisture that can collect in conduit over time. If you really want to use it it would do better either below frost line or with positive venting to keep moisture out.

Exactly the point that I'm making here.  A rework is much easier and less time consuming if the coax and other lines ARE in conduit.  Doing the installation with conduit does take more time and money the first time, but you'll never be sorry, especially if you have the need to pull more cables in the future--or if you need to pull back a cable because of a fault.
« Last Edit: July 12, 2011, 05:24:50 PM by K1CJS » Logged
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