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]

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/prod...56&div=2&l1=testers&l2=testers_coax&l3=33-856

You also need one of these: http://www.idealindustries.com/prod...92&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 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.