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Speaker wire to span utility poles outdoors?

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Don Goguen:
I need to spec wire for a voice only system outdoors at a camp.   I'm replacing/upgrading an existing system that has had many problems over the last few years.   The average span between poles is approx 300 to 400'.  

Any ideas on what wire to use?  

Most of my work is indoors so this is a bit new to me.  I usually only have to figure out if I need plenum or not.   Fortunately I won't be the one that has to run the wiring as the camp has staff including an electrician that wishes to do the work.


Don Goguen

Karl P(eterson):
I am speaking a little out of turn here seeing as I don't have a lot of experience in this field (overhead line suspension) but I do have a little bit of clue, and thus will throw in my thoughts (which may be worthless).

There are two ways to do this. One is to use an Industrial twisted pair control cable, and using metal straps of some sort secure it to a steel cable which is then secured and tensioned to the poles.

The other, easier, and more correct way of doing it is to use variable lay twisted pair overhead suspension phone wire. These cables normally come in a minimum of 6 pairs and three common guage sizes for this wire are 24, 22 , and 19 (at least in what I have seen). I don't know what distances you are running, but you will probably want 22 guage, but do your own math on that one.

With that wire (an example here) You buy the wire, special clamps which secure to the messenger wire and the pole(S) and whatever splice boxes you may need.

A warning: This stuff is not cheap, but is designed to last and engineered to work in these type of environments. In any case, I would probably recommend transformer isolation and line drivers on any sizable run.

Again, consider the source of who this came from, but maybe it will give you some help.

(If you are curious about the company I showed you, It is just a site I found through Thomas Register, and there "main" page is here. There is a telephone number you can call and get pricing information on the cable, splices (if needed), mounts, etc.)

About multiple pairs - you probably want them anyways, for any future expansion, paging, maybe a remote phone? Etc.

Karl P

Karl P

steve g:
Hi Don.

You'll notice, if you've ever watched your cable or telco that for single wire runs, like a drop to your house, they use a cable with a built-in messenger.  For single runs, it makes sense, because you simply run and secure the wire via the messenger.  However, for multiple runs or runs where they want to be able to add more cables later, like runs down main streets, they will run their messenger lines, then come back and pull their cable bundles along side of it and all of that is then secured by a "mesh" that finally secures all of the cables together with the messenger.

It sounds like for your application, you will probably benefit most from a cable with a built in messenger, where everything is on one spool and you run it, secure it, DONE!  Karl also had a good idea of running the cable and attaching it to a simple messenger line.  This effectively would do the same thing in an additional step.

Hope this helps.


Hal Bissinger/COMSYSTEC:
Been down this road before back in the old forum. This is the relevant reply I gave, you can check it all out here: =150095
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Ok. The cable is referred to as IMSA spec cable. It's used for traffic light wiring. I see that there is a 2 conductor 14 ga (I'm assuming that 14ga is sufficient here) messengered cable available. (Messengered cable is also called self supporting aerial or figure 8 (what it looks like when looking at it from a cut end)). This cable is not twisted pair but I suspect that it does have some twist to it. The only thing I don't like is that it has a 1/4 inch stranded messenger. I had hoped for something with a 12 or 10ga solid messenger. 1/4in is a bit of a bear to work with. You cut it with bolt cutters and it's flooded with a tar like stuff so you have to clean it off before pushing it into the dead end grips. Not a big deal though once you get used to it.

What I suggest you do is give Clifford of Vermont a call (1800-769-1837) and ask for their catalog. Though Belden makes this also, I believe Clifford has this cable in stock and will cut and ship whatever length you need. (They might even be willing to send you a sample of the cable so you can see if you are up to this). They also stock all the pole hardware. All you need is a "J" hook to screw into each pole and the building and some 1/4in "Strandvise" dead end grips to hang the cable, 2 per pole and 1 at each end.

At each pole separate the strand from the cable by cutting the web with a knife, cut the strand, clean it, stick the end of each strand in a deadend and hang them on the "J" hook. The cable itself should loop at that point with some slack. You can make this slack as long as you want to connect to a speaker by just stripping more of the strand and cutting it back. You could almost do this on the ground then go up and hang it. You just have to get the sag right so it looks good with the other cables. The dead ends are ratchets, the strand can be pulled through easily to pull the cable tighter. Let go and they tighten up to keep it there. Where the cable enters the building, strip the strand away and discard it for whatever length you need after you attach it to the building with a "J" hook and dead end.
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...then come back and pull their cable bundles along side of it and all of that is then secured by a "mesh" that finally secures all of the cables together with the messenger.

Steve, that's not mesh. It's called lashing wire and is put there by a lasher. Lashing is normally done for most large aerial installations because most cables are designed to be installed this way. There are a limited selection of self supporting "messengered" cables.

Lashed construction consists first of hanging a steel stranded "strand" along the cable route on each pole. Once this is secured in place the cable or cables are pulled and positioned below the strand with temporary hangers. Then a lashing machine is placed over the strand and cables at the start of the run. The lasher is pulled along between the poles on a rope attached usually to the stringer bucket truck that the crew is using but it could also be pulled by hand (or a horse ) if you can't drive a truck along the route. The lasher has one or two spools of steel wire attached which it winds tightly around the strand and cables as it's pulled to secure them to the strand. At each pole the lasher has to be taken off the cables and strand, moved to the other side by the guy in the stringer bucket and the process repeats. Lashers cost about $1000 if you are wondering.

If this isn't more information than anybody should need, ask some more!


steve g:
Wow!  Thank for all the info, Hal.  I didn't try to go into this and further because I figured the guy was just looking for a quick solution to his simple aerial runs of speaker wire, and didn't want to leave him really confused, but hey.  That's cool.

In a totally unrelated question... maybe it's just me but it seems like sometimes people ask really simple questions about other things on this board like, "what's an edison plug look like?", of course my first idea would be to show them a simple picture of the two vertical blades and a ground prong.  But a lot of the time, you will hear stuff like "well, the NEMA # for THAT connector is..." Well hey, the simple jist is two vertical prongs and a ground prong.  Remember, they asked "what's it LOOK like".  I dunno, just a thought.  I've kinda noticed this over time.  I guess it never hurts to include some extra info anyway...  

Hopefully all our info has helped this guy on his way...



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