Max. Length of Coax RG-6 4

[alokwww]

Hi, a few months ago we installed CCTV cameras all over our theatre but one of them never worked. It is the farthest camera. I'm not entirely sure how far it is but I know all cabling and terminations are okay because we've tested it from different junction points, but the camera still doesnt show up on the monitor. What's the maximum length for RG-6 Coax? I believe it's dual shielded but I'm not sure about that. Can anyone think of anything else that could be causing the problems?
Thanks
-Alok

 

[ANFPS26]

RG-6 up to 1500 feet:

http://www.ikegami.com/cb/products/pdf/tech/choosing.pdf

Jim

 

[AvayaNovice]

Can you get a TDR on that cable to get an idea of how long it is?

Have you tried hooking up a monitor directly to the camera to eliminate the possibility of it being bad?

Have you used a signal meter on the termination where the monitor is to see how much loss you're looking at?

You may want to try an inline signal amplifier, see if that fixes it.

RG-6 should work at 1500 feet if your signal is even, without any loss -- but that's not very likely.

I'd say cruise over to your local telecom distributor and pickup an inline signal amplifier.

Nick

 

[alokwww]

Well, the run definately is NOT 1500 feet. I would say it's no more than 3-500 feet... lol. The camera is fine; we have hooked it up directly to our monitor. We've also tried putting the monitor in our electrical room where one of the junction boxes is, and the camera works from there, and if we move the camera into the electrical room and the monitor in its proper place, it even works from there! That's why I though maybe all together the distance could be too long but I guess that's not the case. We don't have a TDR(I actually don't know what that is but I assume its something to measure distance of the cable, and I know we dont have anything like that). We don't have a signal meter either; is it possible the the signal loss overall could kill the signal over even such a short distance (I know that some of the splices aren't so good)?

Okay well thanks for your responses. Hopefully I'll get this thing working! A star for each of you!
Thanks
-Alok

 

[AvayaNovice]

Probably not. Take a look at the monitor (assuming you're seeing snow). Then unplug the coaxial connection from the camera to the monitor, see if you notice any changes. Picture changes overall mind you, not temporary changes (ie. the cable being jiggled in the F connector).

I'd say it's a bad connection somewhere. When you say you know that some of the splices aren't good, are they F connectors into barrels or something? Explain further...

Even if the connection wasn't very solid, the signals should still transmit over even if there's a small gap or anything.

If your splices are F connectors and barrels, try inserting your monitor at the splices, seeing if your signal is weaker and weaker.

A TDR is a time domain reflector. I guess to generalize it, it's kind of like sonar... it sends signals that allow it to estimate (very acurately) the length of a cable. I've never used coax with a TDR, but I imagine you'd have to modify the cable settings quite a bit (as each cable is different, in order to make a TDR accurate you have to provide the device the cable's properties, ie. core diameter -- etc.)

Do you have a tone and probe set? If so, try putting tone on the cable and see if you can pick it up on the other side to make sure you have continuity. If you don't... try putting some voltage over the coax, even a battery would work (postive to core, negative to sheath) and see if you can pick it up on the opposite end with a multimeter (also short the voltage to insure you're picking it up without any other shorts or opens in the cable). That'll allow you to make sure the cable is correct and all continuity is in place.

 

[MasterofNone]

My suggestion would be to get a new spool of cable (500ft or if you have one) terminate both ends on the spool and check this runs on your system. All being well, run the cable without breaks.

Sounds very much that your problem lies within the splicing of the cable.

 

[daronwilson]

(I know that some of the splices aren't so good)?


So you know you have a circuit with bad splices, but you come here and ask what could be wrong? Perhaps if you just fixed the bad splices and checked it out?

A TDR is a Time Domain Reflectometer, it is used to measure the length of a cable. If you don't have one, and you don't have a signal meter, perhaps you should invest in some of the necessary equipment if you are going to be doing the work.

More to the point, hopefully you have a multimeter. Those are pretty easy to come by. I would check the resistance of the cable by hooking a 1k or 100k resistor at one end from the center conductor to the ground, then go to the other end and measure the resistance. I'm not going to look up what RG6 should be, but you should probably read within 100 ohms of that your resistor is. If you read less than 100 ohms total, you may have a short on the wire. If you read a very high resistance, you likely have an open.

As with any wiring, fix what you know is wrong first, then test.

Good Luck!

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[ANFPS26]

Excellent advice, daron!

Jim

 

[alokwww]

Okay, well I'll try all these things and let you guys know what I find. Thanks for your responses!