Subscriber Discussion

Tracing Coax - Moving A Couple Of Analog Recorders To Another Location Along With The Coax Cable Runs

UI
Undisclosed Integrator #1
•Nov 05, 2017

Hi. I am not an installer, just an experienced end user.

I am moving a couple of analogue recorders to another location along the coax cable runs. In effect I am moving the recorders closer to the cameras along the coax. The coax is stretched along cable ladder trays along the roof. There are network, power and signal cables along the coax.

Tracing the cable by eye or hand will not work, because of inaccessible portions of the cable run. I do not know if all the coax is mine. And my cable is of different ages, so I can't just pick a type. I know that there are dead cables from earlier installations up there, so counting is also not an option.

I have tried toning with a fluke intellitone pro 200. But even with the cable disconnected at both ends, and connecting the toner, I only get a tone at the other end. Nothing along the cable. Just hisses from all the different cables.

As a last resort, before starting to pull all the cable back towards the new location, I was thinking that I could try to "tap" the signal from the cables. I only need to be able to verify that the signal is from one of my cameras, so quality of the image is not a concern. I would like not to cut into the cable, but I will if I have to.

Would I be able to pick up the signal just by, for instance, having a wire crossing or coiling around the coax? Or do I need to cut in to the core and touch it? Would It be enough to strip off some shielding?

I will be doing my own experiments tomorrow. But I would love some insight from someone who has done something like this before. I would save a ton of hours and hassle if I could just cut and terminate the cables at the new location.

Thank you for your attention:)

U
Undisclosed #2
•Nov 05, 2017
IPVMU Certified

I have tried toning with a fluke intellitone pro 200. But even with the cable disconnected at both ends, and connecting the toner, I only get a tone at the other end. Nothing along the cable. Just hisses from all the different cables.

IMHO, your not listening to the cable that you’re injecting.  You say that there are inaccessible parts of the run, maybe there is another path that splits and doubles back in that space.

The fluke is very sensitive, I have a similar model and I can’t imagine it hissing in the middle but getting tone at the ends.

Do you have a TDR?  That could be helpful because it will tell you the length of the cable which might give some clues.

Would I be able to pick up the signal just by, for instance, having a wire crossing or coiling around the coax? Or do I need to cut in to the core and touch it? Would It be enough to strip off some shielding?

Maybe somebody has an inductive tap for video over 75 ohm coax, but I haven’t seen it.  You could try using a vampire tap (top of image) though for minimal damage.

(1)
UI
Undisclosed Integrator #1
•Nov 05, 2017
In reply to Undisclosed #2

IMHO, your not listening to the cable that you’re injecting. You say that there are inaccessible parts of the run, maybe there is another path that splits and doubles back in that space.

If I probe outside the cable a foot from the end, all I get is the red blinking light in digital probing, and no tone in analogue toning. The red light seems to say it is picking up something, but can't say if it is the toner signal. I tried it on a cable that I know the path of, because the camera is near the new location for the recorders. I imagine the shielding is picking up a lot of noise, and any tone along the shielding get distorted. And the tone on the core is of course shielded by the outer shielding. 

Do you have a TDR? That could be helpful because it will tell you the length of the cable which might give some clues.

I do not have any tdr tool. But the length does not really help in determining which cable is mine. 

I do not have a vampire tap, so I was thinking of just stripping the cable on one side, and connecting it to a test screen. The problem is that one or two of the coax cables may be an antennae cable for some radio and pager equipment they have. I don't want to disrupt that, or short something out.

The building is over 20 years old, and none of the cabling got marked or drawn on a blueprint. Everything is "I'll do it when I get time." and then never gets done.

 

UI
Undisclosed Integrator #3
•Nov 05, 2017

After all I have read it seems safer and simpler to just extend the cables even though they are back tracking.  

(1)
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Jon Dillabaugh
•Nov 05, 2017
Pro Focus LLC

Why don't you physically pull the cables? Start from the recorder end and give a slight tug to identify them in the tray, pull some slack back, then head further up stream and pull that slack until you get it where you want to go.

UI
Undisclosed Integrator #1
•Nov 06, 2017

The reason why I don't want to pull the coax back, is because it's not cable ladders all the way. The last bit is just a tangled mess. I would have to go really slow so that I don't pull the roof down. Pulling the cables would make it a week of work instead of a two day job.

UI
Undisclosed Integrator #1
•Nov 06, 2017

I found out what I was doing wrong with the toner and probe. I had to ground one of the toner leads to get at loud tone along the wire. Now it is really easy to get a good tone.

So problem solved. Thank you all for your input.

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