Shielded cable for towers questions

So, in the next week or two we’re planning on putting up a new AP with the associated backhauls to our existing towers and it’ll be my first time doing tower cabling.

In the past, our oldest towers didn’t have shielded cat5, just outdoor unshielded. One tower even had bright blue indoor crap used for the timing cables for some reason (hope to replace after winter just because).
The newer towers that do use shielded cat5 just have the ends terminated with normal old rj45’s and no apparent drain wires or anything. So they aren’t much for me to learn off of.

For the new AP and backhauls we’re putting up, I had a roll of shielded cat5 and bunch of shielded rj-45’s ordered up. I planned to use it for the timing cables as well, based on what I’ve read, just with rj11’s (which aren’t shielded anyway…)

Were the shielded rj-45’s actually needed? How does a guy usually ground the shielding or does it need to be grounded? What’s the trick with grounding the foil anyway, since the stuff we got seems to have no drain wire that I can see (just a bit of nylon string).

Any advice on working with this stuff?

(Edited for readability.)

Yes to use STP you need STP RJ45’s…

I use these: … ventPage=1

They require a special crimper for the strain relief in the back. I can’t seem to read the part numbers off my Amp crimper but you can get them from Best-Tronics as they are required for the STP connectors they sell.

the bottom end of the cable run is the location where you tie the drain wire down to the grounding system. This usually is grounded out inside the 600S protector to the screw terminal, or through the STP RJ45 connection in the CMM3 protector.

Are you familiar with how to make STP RJ’s?

What kind of ground system do you have installed currently?

Are you familiar with how to make STP RJ's?

Nope. First time working with them. The ones we bought are these three piece RJ. The metal jacket is also a strain relief by the looks of it. Bit different from the one you linked to. Not sure how to describe it, but I could probably post some pictures later.

What kind of ground system do you have installed currently?

As in, do we use a 600SS or what-not? Currently no and as far as I know, none of our towers do. (Though I do have a large Trantector Surge Suppressor sitting in a box here that will be installed at one tower at some point in the near future too.)

Also, where is the drain wire coming from? All descriptions I see suggest it's already in the casing of the cable except the stuff we got.

The three piece RJ’s with the little plastic insert, and the strain relief that is separate?

If you are using the Transtector CMM3 protector (unit with the RJ45 jacks on the inside instead of the traditional screw terminals for the connections) then you just make the STP RJ’s like standard RJ’s. My experience is that the jacks on the inside of the protector have their metal shields (the hood that surrounds the jack itself) is bonded to the ground lug on the PCB. Ensuring that the drain wire is crimped down to the strain relief which is also wrapped around the foil after it is folded back is crucial. Make sure you sweep the cable with an RJ45 loopback tester that has the option to test the shield… Most testers have this option. This will ensure the cable is made correctly, and also ensure that the shield/drain is connected through entirely.

The primary purpose of using STP is not lightning protection, but to ensure that the ethernet is not corrupted from RF interference. I used to just put STP wire from the radio to the protector, and use UTP from the protector to the CMM or PSU. I have recently found that I am experiencing CRC errors on one BH on a site. I suspect it is due to noise on the UTP inside the shelter (high RF environment). I am now working on replacing the short UTP to CMM and CMM to Cisco switch with STP cable made with STP RJ’s. It is tedious and labor intensive to do it this way, but it is the right way. I’ve been on a lot of professionally engineered sites from Motorola, and they use STP on all ethernet jumpers/runs. If they do it, I do it.

Thanks for the info. I agree, having it figured out and doing it properly is definately the way to go. I have one AP that’s timed from its BH that constantly loses and gains the GPS sync, and I think it’s due to the way the timing cable was made. Mind you, the damn thing works pretty good, no complaints (knock on wood), but the message spam about it in the event log is worrisome just the same.

Also: Yeah, that’s RJ’s I’m working with. The little insert goes inside the the almost normal looking piece with the contacts, then a metal jacket goes over the back of that. The little insert looks like it makes getting the actual pairs in their correct order a bit tough.

Any tips on folding back the foil? I was having a heckuva time getting that outmost plastic to peel off so I could work with it. I can see I’m going to have to just sit down with it a bit longer and keep fiddling with it. A diagram with steps would make it easier to see what goes where.

the cable makes the difference… not all STP are equal. We use Belden 7919A for all our tower runs up tp 450 ft. it cost more but the results are well worth the cost. Yea I know the rules …100 meters… but I can garantee you if you use this stuff with the shieled RJ45 connector you will not be disapointed. Hyperlink sells a kit with all the strippers and crimpers spend the cash and get a GOOD set again makes a difference. after you set your wires up to go into the connector use a pliers to squeeze the plastic on the cable just enough to go into the connector for a good mechanical connection…then wrap the drain wire around the end as you insert it into the connector and insure that you get the wire under the crimp for a good electrical connector… try a few before going to the job… I’ve done hundreds like this and it becomes easy.
Allied Electronics sells a good connectorand so does CTI in BurrRidge,Il.

Hope this helps…

I do a two-step process to remove the jacket. I use a regular cat5 stripper: … ventPage=1

I use the stripper to score about an inch back on the jacket. I make this cut using the tool so it is deep so spin it a few times around on the jacket so it cuts the jacket and foil. Don’t remove this yet. Use the strip tool to score the jacket about an inch back from where your first cut was. Spin the tool only once… cut the jacket BARELY enough to score it. Grab the jacket where you just scored and hold it firmly. Break the first part of the jacket off, snapping and twisting it. Be careful to not handle the cable too rough as you want the second portion of the cut jacket to remain intact.

Take a very sharp razor knife and skim the jacket from the scored part to the end. This is very hard to explain online, but the best way I can think of explaining it is skin it like you are using a knife to sharpen a pencil. Does that make sense?

You have to be very gentle on this part so that you do not break the foil off, or cut into the foil. After doing this you should now be able to remove the jacket carefully, and be left with the foil shield completely intact. The foil will have a split in it, so fish out the drain wire, and pull the drain down and back through this split. The foil at this part will now be somewhat open. You can do two things: work the foil back down around the jacket, folding it carefully. Or, I do this and I am not sure if it is 100% in accordance with mfg’s suggestions but I do it anyway becaus I still feel it is a good conection… take your razor and gently cut the foil where one side of it goes down into the cable, and peal it around so its now open and flat. Don’t peal too much as you want to have a smuch of this foil intact. Wrap it around the cable and smooth it down so it folds back over around itself encompasing the cable. Prep the pairs, slip the plastic inside piece over the pairs. Trim pairs as needed to make sure the jacket is able to be completly inserted into the RJ45 plug. This is critical. I see a lot of WISP installs from our competitors and other people that fail on this part. The jacket and ultimately the foil MUST make contact INSIDE the RJ plug. This is how the plug and the foil are interconnected, thus completing the shield circuit. Crimp the connector.

Now you are left with excess foil and the drain wire hanging out.

Take the drain, and lay it flat against the foil. Take the metal strain relief and secure it to the plug. Make sure the foil and drain are still touching ,and crimp the strain relief down. This ties the drain secure to the foil, and to the strain relief. This also completes the circuit.

I should get some photos… the whole process is confusing unless you are shown.

Okay, I’m seeing a few different varieties of the cable itself. Here is the stuff I’ve got (though not from this store…) … D2603.aspx

I’m having a helluva time getting down to that blue-coated-shielding stuff without ripping it up. (I won’t be able to get a hold of better cable strippers/crimpers for this week unfortunately, if that’s what I need.)

I guess the best way to show where I’m at is to show what I’ve got so far. This is my first attempt:

She ain’t pretty! :shock:

I am tempted to say screw it for what I need to do this week and just use regular ends (stick with what I know for now). It’s a 30 foot wooden pole (a telephone pole alone in the middle of a field) that may or may not become a permanent setup depending on how many people we can reach from there (otherwise we have to build a tower or something.) Then just take the time to figure out how do this right and order in the right tools, parts etc.

Hmm I’ve never used connectors like that before.

Usually the first few are nasty. My first few were done up at the top of a 100-foot Rohn25G tower. It was about 105* out that day, all day. I was wiring a full cluster and the ground hand didn’t have a clue as to how to make them (neither did I, but I sure figured out that one fast).

I’ve tried many different techniques since coming up with the one I attempted to explain, but never have seemed to be able to best it. The two strip process combined with the skinning of the cable with the utility knife is for me, by far the best way.

Not using the shielded connectors is a waste. The whole assembly needs to be shielded so that it can properly drain RF interference. Otherwise, it’s a half-done attempt and runs the possibility of turning the foil shield into a huge antenna. Tieing the drain to a good ground system will help, but it won’t be complete until the shield is fully captivated and tied to the drain and ultimately the RJ jack.

How about having the bottom connected, but not the top into the AP itself? I can’t see there being much difference at that end. (And that’s the main thing we want in place this week, the backhaul and electrical can happen whenever.) I can do the other end properly later, even next week if I have to.

Since the AP is going to be getting it’s timing from the backhaul (at least for now) we’ll be using a timing cable. I’ve heard that even it’s supposed to be shielded, but does an shielded rj-11 even exist? Would I be better off connecting a ground wire to the foil and grounding that to something else? The more I think about about it, at the end of the day, that’s gist of what I’m trying to do isn’t it? And when I really start overthinking the situation, same goes for the data cable, right? What’s to stop me from using a normal rj 45 and then wrapping a piece of copper wire around as much of the foil I can expose as possible? Would look hokey, but should do the trick shouldn’t it? Because I’m not trying to ground the contact around the female end at the AP, just the shielding in the cable itself (because it’s like a big antenna otherwise, like you said right?)

I’m going to stop my rambling of questions here now. :slight_smile:

Well it goes against my judgment but at least get the drain wire connected to earth.

Here is a doc I found for you. They basically do everything how I have figured it out. These are the actual connectors too that I use. They have an actual tool for the plugs too, instead of my two-step AMP tool used for the AMP plugs. Same difference though, and it works just the same. For anyone doing these in the future though I’d get the correct crimp tool.

Choose the termination instructions for the 7921 cable.

Thanks for your help amd phreak.

That set of instructions looks like it makes sense. It looks like the inner casing is the metal jacket with a second braided jacket and then finally the outer plastic casing? I suspect my rj-45’s were meant to work with the cable in those pictures as opposed to the cable I have. I bet if we had a roll of cable like that, the jacks I have would probably work fine. Either that or I need a special jack. :?

The heat shrink looks like a nice touch and makes sense. That whole setup looks sharp. Gonna hafta talk with our supplier for future material.

Keep in mind the doc shows a different type of cable than what you would normally use.

I use those connectors shown in the doc (from Tessco like i said earlier) and the Belden 7919a cable. The 7919a is very similar to the Best-Tronics cable that is actually specified in the Motorola documents for Canopy. Most of our sites were not constructed by me, but rather the guy before me. He used the Best-Tronics cables but didn’t use shielded ends or proper grounding techniques. I have since fixed all of that. It was a PITA but it had to be done.

I’d stick with the 7919a as it is cheaper than the Best-Tronics, meets the same specifications (as far as I can see), and is fairly common to suppliers like Tessco, Talley, Hutton, Wincom, etc.

And connectors are your choice. AMP or those that I have referenced. I am sure there are others, like those without strain reliefs but they are such a pain in the ass to use because the opening where you insert the cable into the connector is not extra large… which means you have to follow a completely different method of installation. I tried finding the Belden doc on that method but was not able to. Just trust me it sucks. You have to use my technique to strip the jacket and foil, and then you have to fold the foil back. Then you mash the foil/jacket down flat so that it can be inserted easier into the RJ plug… i hate that.

I finally found the brand of my rj-45’s. … =137520400

Hmm never have seen those before.

AMD, is the 7919a the cable that has bonded pairs you have to split apart before you can put an end on it?

louis.arsenault wrote:
AMD, is the 7919a the cable that has bonded pairs you have to split apart before you can put an end on it?

Nope. If it was I'd never suggest it. :) I hate bonded pairs.