Pull Damage to Coax?

[big john]

I have quite a few runs of RG6/U between 100' and 300' in length. They are part of a plant wide CCTV system. I can't properly measure signal strength on these cables, but some of the cables are not broadcasting any images to my DVR or monitor.

I know the cameras connected to the RG6 are working.
I know my DVR and monitor are working properly.
The problem seems like it must the RG6.

I'm not a datacom guy, this is my first rodeo. How easy is it to damage coaxial during pulls or through tight bends? (Some of it connects to cameras through 3/4 LBs.) And could this account for enough signal degredation to explain the fact that these camera channels aren't broadcasting?

Any help at all would be appreciated. I'm pulling my hair out!

-John

[hbiss]

The first thing I would do is check the connectors. I'm willing to bet the farm that you screwed them up by what you used or how you installed them. Then I would check for simple continuity and shorts on the runs in question.

It is very unlikely that even tight bends are going to cause a no signal condition. However it is possible to damage the cable with excesive pulling force.

-Hal

[Sierrasparky]

Could the 300 legnth run be a issue.
What kind of connectors did you use?
Make sure you cutter cleanly cuts the the dilectric and does not damage the conductor. Make sure there are no stray braid wires.
Make sure the connector inside shoulder is flush with the Dilectric.Tight bends and kinks have been known to degrade signal.

[hurk27]

One of the more common problems I have been finding, is when when someone uses a spin around cable stripper, they fail to look at the center conductor to make sure no shield strands are shorting out the center conductor, the cheaper cable strippers will do this, and as long as you look real close to the center conductor, to make sure this don't happen, or you can take a continuity test with both ends of the cable disconnected.

I have found this problem many times lately, and most of it was after the cable guy cut our ends off, and installed their ends:roll: even when we both use snap-loc ends.

[wireguru]

even if the cable was damaged, you will see something on the screen unless you completely broke the center conductor. composite video is much, much more forgiving than say digital cable due to the lower frequency. As someone else suggested its either a strand of shield touching the center conductor, or if you used one piece compresssion connectors the center conductor may have not lined up with the center pin and bent over.

Disconnect the cable at both ends, and meter between the shell and center pin of the connector and see if you have a short.

[JFletcher]

"The first thing I would do is check the connectors."

Same here. Also note that many BNC connectors will not properly fit RG6 as they are designed for the thinner (and correct) RG59.

[hbiss]

I have found this problem many times lately, and most of it was after the cable guy cut our ends off, and installed their ends...

Probably subcontractors and they buy their own tools. This just goes to show what I have been saying all along about crap tools from HD, ebay etc. and even though the tools may have a name on them that you know.

If you use tools from established CATV tool companies and maintain them properly you won't have problems like this.

-Hal

[big john]

So, ya'll may have called it again: It does look like a connector problem. I may well be screwing the up, but I've tried to be darn careful, especially when I realized I was having problems, yet the problems persist.

I used Ideal's RG-6 compression BNC connectors and attached them with the Omin-seal Pro XL tool....When when someone uses a spin around cable stripper, they fail to look at the center conductor to make sure no shield strands are shorting out the center conductor.... The darn connectors and crimper came with just about nothing in the way of instructions, so this is how I've been terminating this coax:
Use a spin stripper to expose 1/4" of center conductor (with no nicking), and 1/4" of the copper braid (with minimal nicking).
Fold back the copper braid so that it lays flat against the outer jacket of the PVC, and exposes the foil shield. From the sound of your description, I shouldn't be doing this. Otherwise, how would the shield strands even be close to the center conductor?
The connectors have a blue band around them to show the maximum depth the cable can be inserted. I mark the cable at that depth and then push it on. Some of the connectors do seat more than others, so there may well be a connection issue there.
Put connector in tool and crimp until tool handle closes. Check to see if there are any copper strands sticking out the back (which I found from experience, means the connector isn't seated.)
Aside: Some of the connectors that I thought I did perfectly, that went on very easily, are on problem cameras. Some of the ones that went on with a lot of difficulty are on working cameras. So I'm not totally convinced that "force" is an indicator of "trouble."

Thanks for the help so far.

-John

[nhfire77]

http://base0.googlehosted.com/base_media?q=http://www.homedepot.com/catalog/productImages/400/79/7963319a-0cf1-4a8d-8586-3243ad761cd7_400.jpg&size=4&dhm=e801587d&hl=en&mode=1

I use this style , precision is a must, and you can see what you are doing and the cable 100% of the time.


Not as fast as some of the other options, but I've done over 1000 RG-59 strips with these, never once a problem. They make them from RG-6 also

[nhfire77]

Oh yeah

Do you have an Oscilloscope? That is the old skool way of troubleshooting and it works.

[wireguru]

So, ya'll may have called it again: It does look like a connector problem. I may well be screwing the up, but I've tried to be darn careful, especially when I realized I was having problems, yet the problems persist.

I used Ideal's RG-6 compression BNC connectors and attached them with the Omin-seal Pro XL tool. The darn connectors and crimper came with just about nothing in the way of instructions, so this is how I've been terminating this coax:
Use a spin stripper to expose 1/4" of center conductor (with no nicking), and 1/4" of the copper braid (with minimal nicking).
Fold back the copper braid so that it lays flat against the outer jacket of the PVC, and exposes the foil shield. From the sound of your description, I shouldn't be doing this. Otherwise, how would the shield strands even be close to the center conductor?
The connectors have a blue band around them to show the maximum depth the cable can be inserted. I mark the cable at that depth and then push it on. Some of the connectors do seat more than others, so there may well be a connection issue there.
Put connector in tool and crimp until tool handle closes. Check to see if there are any copper strands sticking out the back (which I found from experience, means the connector isn't seated.)
Aside: Some of the connectors that I thought I did perfectly, that went on very easily, are on problem cameras. Some of the ones that went on with a lot of difficulty are on working cameras. So I'm not totally convinced that "force" is an indicator of "trouble."

Thanks for the help so far.

-John

that style of compression connector sucks. I have installed hundreds upon hundreds of them and have had nothing but problems (these werent ideal but the same style) What happens is, if the center conductor isnt perfectly straight and perfectly centered it goes off to the side of the pin its supposed to go into.

There is another style of RG6 compression BNC now with a loose center pin you crimp onto the center conductor, then insert the cable with the center pin already on it into the connector, then use compression tool. These work much, much better. Another thing to do if you cant get these, is just use compression F connectors and F to BNC adapters.

[wshoard]

Are your connectors designed for RG-6?

You can damage coax while pulling it which can cause several types of problems. The main 3 are, High End Rolloff, Low End Rolloff, or Suckouts. Also these can be caused by exceeding the bend radius of the cable. General rule of thumb is 20X Jacket Dia, but check sheet for your brand of cable.

Get one of theise from Lowes to test your cable: http://www.idealindustries.com/prodDetail.do?prodId=33-856&div=2&l1=testers&l2=testers_coax&l3=33-856

You also need one of these: http://www.idealindustries.com/prodDetail.do?prodId=33-892&div=2&l1=testers&l2=testers_coax&l3=33-856

The first tester is very good, I use mine several times a week, it's cheap too, the second one isn't! :(

I agree with wireguru, the fastest way and safest is to use F type connectors and a F-BNC adapter.

[JFletcher]

General rule of thumb is 20X Jacket Dia...

It's closer to 6x cable diameter for RG59/6, or 1.5-2". A 20x radius certainly wouldn't hurt, but 4 square boxes do not have enough room to accomodate such a large sweep.

~~~~~~~~~~~~~~~~

wireguru is correct: unless you completely broke the center conductor (or the braids/foil), you will get some signal. Barring a bad termination, the only other way you won't get any signal is a short in the run, like a nail or screw driven though the cable. A continuity test will tell you if either is the case. I'd recommend one of these (http://www.web-tronics.com/mincoaxtesbn.html) for that purpose - they won't break the bank.

[egnlsn]

The ANSI/TIA/EIA Standard says the minimum bend radius for coax is 20X the diameter of the cable when pulling, and 10X the diameter of the cable when in a fixed (final) position. Same as fiber.

A continuity tester will only tell you if a cable will pass d.c. Won't tell you a thing about its capabilities of passing r.f.

[JFletcher]

TIA/EIA also specs no more than two bends in conduit and pull boxes every 100'. That would be nice...

10x radius of a .25" coax cable is a 5" diameter. Again, there's no way to get that in a 4" box that also is, at best, 3 1/8" deep w/ a 1" mudring (more applicable to CATV than CCTV, but I digress).

I'll agree that a continuity tester is only useful for continuity, but the OP had no signal, not "bad signal".

I'll also agree that 20x for pulling is doable. If the cable is pulled correctly, short of a manufacturing defect or damage by someone else, there will be no problems with it.

[wshoard]

TIA/EIA also specs no more than two bends in conduit and pull boxes every 100'. That would be nice...

10x radius of a .25" coax cable is a 5" diameter. Again, there's no way to get that in a 4" box that also is, at best, 3 1/8" deep w/ a 1" mudring (more applicable to CATV than CCTV, but I digress).

I'll agree that a continuity tester is only useful for continuity, but the OP had no signal, not "bad signal".

I'll also agree that 20x for pulling is doable. If the cable is pulled correctly, short of a manufacturing defect or damage by someone else, there will be no problems with it.

Belden, in their cable spec sheets list a lot of RG-6 as 2.75" bend Radius which is 5.5" diameter. A easy way to tell what the bend radius should be, is look at the diameter of the spool it's shipped on, half of that is close to the radius.

I agree about the 4x4 box, coax should never be run thru a 4x4 box, much less a LB.

[egnlsn]

10x radius of a .25" coax cable is a 5" diameter. Again, there's no way to get that in a 4" box that also is, at best, 3 1/8" deep w/ a 1" mudring (more applicable to CATV than CCTV, but I digress).
Agreed. That's why the last nail or clip should be a foot or two away from the box, allowing the excess cable to be pushed up inside the wall rather than coiled up inside the box.

[big john]

I appreciate the help.

I honestly don't believe it's cable pull-damage at this point, nor do I think it's a radius problem. I took a piece of cable and hooked it up to a camera and monitor and proceeded to kink it clean in-half with my kleins in several places without signal loss.

I think the problem is these stupid Ideal connectors where you just have to "guess" that it's crimped on properly. I may well go with the type-F to BNC adapters, unless anyone recommend a brand of RG-6 BNC compression connector that fits over the center wire of the cable?

Thanks.

-John

[nhfire77]

I appreciate the help.

I honestly don't believe it's cable pull-damage at this point, nor do I think it's a radius problem. I took a piece of cable and hooked it up to a camera and monitor and proceeded to kink it clean in-half with my kleins in several places without signal loss.

I think the problem is these stupid Ideal connectors where you just have to "guess" that it's crimped on properly. I may well go with the type-F to BNC adapters,unless anyone recommend a brand of RG-6 BNC compression connector that fits over the center wire of the cable?

Thanks.

-John

This? http://www.smarthome.com/manuals/849323.pdf

I wouldn't buy from that website but..

[wireguru]

This? http://www.smarthome.com/manuals/849323.pdf

I wouldn't buy from that website but..

ive used those. its hit or miss whether you can get the center conductor into the pin. Theres another kind out there where the center pin is seperate, you crimp this on first, then insert the cable into the compression connector.

[big john]

So, a little update: I've gone through almost 70 Ideal 89-048 connectors to try and do what should've taken 32.

I took an inoperable crimped connector and cut it open. I found that if the coaxial is stripped 1/4" off the center conductor and 1/4" off the braid, when you push it into the connector the coaxial insulation reaches the stop inside the connector and the center conductor is barely making contact with anything!

I'm not sure what the heck Ideal was thinking, because those are the stripping recommendations on the package, but it's almost physically impossible for them to work that way! :mad:

I changed the strip lengths to about 3/8" and 3/8" and I've gotten slightly better success, maybe at about 75-85% work the first time out, but I'll tell you what: I am all done with Ideal compression connectors.

Not for the life of me will I ever use these again, and I hope someone reads this and maybe saves themselves the hassle. The next project I'm gonna go with the simple type-F crimps with the adapters.

Thanks for the help you guys gave me, and thanks for tolerating the rant.

-John

[billsnuff]

Sounds like Ideal is crimping you style. :D :D

[weressl]

Could the 300 legnth run be a issue.
What kind of connectors did you use?
Make sure you cutter cleanly cuts the the dilectric and does not damage the conductor. Make sure there are no stray braid wires.
Make sure the connector inside shoulder is flush with the Dilectric.Tight bends and kinks have been known to degrade signal.

Cable Type*Maximum Distance
RG59/U*750 ft.
RG6/U*1,000 ft.
RG11/U*1,500 ft.

[LarryFine]

Theres another kind out there where the center pin is seperate, you crimp this on first, then insert the cable into the compression connector.I think Amphenol is the brand you're talking about.

[LarryFine]

Sounds like Ideal is crimping you style. :D :DBoo-hiss! :roll: (;))

[LarryFine]

I'm not sure what the heck Ideal was thinking, because those are the stripping recommendations on the package, but it's almost physically impossible for them to work that way! :mad:
I rarely strip per instructions, but how eyeballing the connector tells me, especially if I had trouble doing it their way.

I'd rather strip the center wire the length of the pin, and let the pressure push it back into the dielectric if it needs to.

[Speedskater]

Ideal seldom has useful instructions available for any of it's co-ax tools. I think that for the most part they just re-package other manufacturers tools.

[hbiss]

This is why I have always said to stay away from all but the traditional manufacturers of coax fittings and tools. It seems many electrical manufacturers have been cashing in on selling this stuff to the electrical industry because they have name recognition. Most times the quality is just not there like it is with their regular electrical lines. So don't think because it has a name on it that you have known for years that it is any good.

-Hal

[quogueelectric]

I use the data shark crimper and have about a 999% succes ratewith ideal crimp conns.

[zbang]

It's been fun following this topic. In no particular order:

* make sure that the connectors you have are for the exact coax you have. Not all "RG-6" is created equa (some people use that as a generic name, not a real spec); you need a close match for the diameters. I prefer Amp or Amphenol connectors. I've also used the ones that Miles-Tek sells, and usually avoid King brand.

* use crimp-on center pins. More reliable IMHO.

* get a good stripper, I like the Pallidin ones and use the correct blade cardtridge for the connector. Replace the blades every once and while.

* use the strip dimensions as per the connector spec, "about 1/4" is often wrong. The package should have the numbers. Sometimes it'll be like 0.250 for the center and 0.365 for the jacket.

* Get a crimper with the correct dies for the coax you're using. Again, different versions of RG-6 can have slightly different diameters. They're usually OK, but some specialty products are just enough different. (For instance, AT&T 734a "digital" coax. Great stuff, very low loss, looks sort of like RG-6. Isn't at all.)

In almost 30 years of doing this stuff, with the correct parts/tools, I have maybe 1 in 100 or better that won't pass a TDR test. (In the way of contexts, I've been doing these for networks and TV studios, not home cable-tv installations. Your mileage may vary.)

BTW, one of the biggest errors is using 50 ohm connectors on 75 ohm coax. They'll fit, sort of, but usually won't pass a test.

[wireguru]

I think Amphenol is the brand you're talking about.

the ones I had were chinese :grin:

[egnlsn]

BTW, one of the biggest errors is using 50 ohm connectors on 75 ohm coax. They'll fit, sort of, but usually won't pass a test.
Wow. So good to see someone actually bring that up. One of the differences is the pin size, which can cause grief if the mating connector is the other impedance.