CCTV at farm gate

[sparc]

I agree the coax itself should be your focus at this point.

 

[Wazrus]

I agree the coax itself should be your focus at this point.

From Wazrus
The consensus seems to be that the coax is indeed faulty and as suggested, I might try to take it back to the reseller. Having said that, I've tested it for continuity and it seems OK and as has been discussed, I reckon I've become pretty expert at fitting the compression connectors.
It seems I didn't explain my 'test' setup very well, such as it was.....Well, before pulling all the cable runs through the existing conduit and as a test, I unwound all 100m of coax on the ground. I simply laid it out: 50m on the way out to the gate, 50m on the way back, leaving it in a wide 'loop' and leaving the two runs of cable about 2-3m apart and connected the ends to camera and monitor. Nothing exact or remotely scientific about any of it.
Those two (out and back) runs crossed and re-crossed the underground supply I mentioned earlier, thus my thought that perhaps the U/G supply was interfering with the signal. That seems not to be the case, if I understand you all correctly.
As a last resort, I then re-arranged the test setup as a 'straight' run of cable, i.e., no loops anywhere, simply straight from camera to monitor, no bends, no connectors except at the camera and monitor, 100m straight, with camera power supply very close to the camera. Bingo! Pictures!!!
I could stand corrected, but it seems a matter of actual practice that one might avoid any 'looping' of coax carrying CCTV signals, or any situation where the same signal is in coax close by. That's my 'hypothesis'....:laughing:
Thanks once again for all your input(s)
Wazrus
PS If you're interested, I'll keep you posted on progress - or lack of it!!

 

[weedpharma]

Wazrus, are you planning to bury the coax? I have a roll of "cable tv" coax (can't find secifications) that I was going to do similar thing. I was woried about burying the cable in regard to corrosion.

Anyone have any knowledge about direct burying coax?

Weedpharma

 

[k0ua]

Wazrus, are you planning to bury the coax? I have a roll of "cable tv" coax (can't find secifications) that I was going to do similar thing. I was woried about burying the cable in regard to corrosion.

Anyone have any knowledge about direct burying coax?

Weedpharma

the cable must be rated for direct burial or it will deteriorate pretty quickly underground.. how fast depends some on your soil moisture conditions, but all coax jackets are not the same.. If rated for direct burial, it will be fine if not... It will NOT be fine. Find the data sheet on this brand and model of coax you have. They are usually published on the manufacture's website.

James K0UA

 

[k0ua]

From Wazrus
The consensus seems to be that the coax is indeed faulty and as suggested, I might try to take it back to the reseller. Having said that, I've tested it for continuity and it seems OK and as has been discussed, I reckon I've become pretty expert at fitting the compression connectors.
It seems I didn't explain my 'test' setup very well, such as it was.....Well, before pulling all the cable runs through the existing conduit and as a test, I unwound all 100m of coax on the ground. I simply laid it out: 50m on the way out to the gate, 50m on the way back, leaving it in a wide 'loop' and leaving the two runs of cable about 2-3m apart and connected the ends to camera and monitor. Nothing exact or remotely scientific about any of it.
Those two (out and back) runs crossed and re-crossed the underground supply I mentioned earlier, thus my thought that perhaps the U/G supply was interfering with the signal. That seems not to be the case, if I understand you all correctly.
As a last resort, I then re-arranged the test setup as a 'straight' run of cable, i.e., no loops anywhere, simply straight from camera to monitor, no bends, no connectors except at the camera and monitor, 100m straight, with camera power supply very close to the camera. Bingo! Pictures!!!
I could stand corrected, but it seems a matter of actual practice that one might avoid any 'looping' of coax carrying CCTV signals, or any situation where the same signal is in coax close by. That's my 'hypothesis'....:laughing:
Thanks once again for all your input(s)
Wazrus
PS If you're interested, I'll keep you posted on progress - or lack of it!!

Yes, but have you checked it for continuity while moving the coax with a helper? That is the very thing you must do. This is the only explanation for why when you loop the coax back and have your test setup all in one place the coax fails and when you stretched it out it worked OK.. the coax must be faulty, and your act of moving it caused the break in continuity. I should not mater a bit if the coax was rolled up in a 2 foot roll, it should perform the same, as long as the minimum bend radius was not exceeded.. and we are talking about 4 to 6 inches here for a minimum bend radius that would cause the center conductor to migrate thru the dialectric (the center insulation) into the shield. I realize you do not have nor probably have any access to a Time Domain Reflectometer, but you surely have an ohmmeter or continuity checker of some kind. If you had one with a buzzer or beeper you could short center to shield on one end and ohm or check the other end and wiggle/move the coax until the open manifested itself. Then remove the short on one end and move the coax and connectors and make sure there is no continuity from center conductor to shield and then repeat this procedure from the other end (to make sure you do not have a compound problem). I am betting you have a coax problem.

James K0UA

 

[JoeL4330]

you already can reproduce the "fault": no signal when there is a (particular) bend in the coax. Set it up so you get the dreaded "no signal" and then check continuity. Consensus seems to be that were you to that you would find a continuity fault.

 

[nikdfish]

Any chance you can borrow or rent a time domain reflectometer or get someone who has one to help out? Network cabling folks use them to ID & pinpoint faults in twisted pair & coax. Use of one can actually provide information on the precise distance from the connection to the fault (if there is one) when you are in a "no signal" condition.

Nick

 

[joshuabardwell]

Any chance you can borrow or rent a time domain reflectometer or get someone who has one to help out? Network cabling folks use them to ID & pinpoint faults in twisted pair & coax. Use of one can actually provide information on the precise distance from the connection to the fault (if there is one) when you are in a "no signal" condition.

Nick

Would that be overkill? I mean, to rent a TDR might cost $1000; another few hundred feet of RG6 is going to run $100 at most. I think Joel is onto something: put the cable back into the "no connection" state, use alligator clips or whatever to bridge the conductor and the ground at one end, and test for continuity between conductor and ground at the other end. If you have continuity, you know the cable is good--but I bet you don't have continuity.

 

[Wazrus]

Weedpharma: Me too! Farming weeds is a growth industry here, too!
The coax I'm using is specified as RG-6/U quad shield: it's branded CRG60E 75 OHM RG6U QUAD SHIELD CATV/MATV/SMATV 11-05-28-0109 047M. It's the goods, as far as I can make out, but that doesn't imply that it's perfect, as many of the posts re my CCTV cabling point out.
From a bit of preparatory reading, Gary Cratt (an Aussie satellite TV guru), suggests there are a few good reasons why you shouldn't bury your coax directly. A few quotes from Cratt's text in his book The Practical Guide to Satellite TV., 7th edition, ISBN 0 646 30682 0; Pages 47 and 48: "RG6-U is often silicon flooded to ensure moisture cannot penetrate either between jacket and braid, and has two layers of aluminium foil sandwiched between two layers of tinned copper braid" and: " Experience dictates that only RG-6/U cable with foam dielectric is suitable for TVRO installations. Cable having a 'honeycomb' air dielectric may have slightly lower (electrical/signal) loss (my brackets), but the risk of moisture entry and retention in the honeycomb structure far outweigh this factor"....
Further: "Once moisture enters a coaxial cable, it can be drawn by capillary action for many metres, causing the braid to corrode and eventually break down"...
More: "For longer runs, heavy-duty cable, called quad shielded RG11 should be used"...
For my money, the cost of conduit far outweighs the pain in the neck factor of having a direct-buried coax run fail due to moisture. My RG6-U will be in rigid PVC conduit, with the ends well and truly 'siliconed' to keep the water out! Partly for reasons of moisture rejection, I've gone to compression-type connectors, as it seems that the crimp-style connectors can allow moisture ingress.
Sorry about the long-winded reply, but I'd suggest you not direct bury your coax and I think those far more knowledgeable than me would say the same. And I'd suggest checking the specs of the cable you propose to use. Also, my 100m of coax cost $A44 and I don't reckon that's a lot of $, even if I have to replace it. It's not underground yet!
Good luck!
Wazrus

 

[joshuabardwell]

Sorry about the long-winded reply, but I'd suggest you not direct bury your coax and I think those far more knowledgeable than me would say the same.

Everything you say is true, but if the cable is rated for direct-burial, then you can direct-bury it--obviously. I think what you're saying is relating to garden-variety RG-6. Here's an example of direct-burial RG-6:

Direct Burial RG6 Coax Cable for Cable TV 'Flooded' CommScope

You can just trench and stick that stuff right in the ground. You may also need special connectors to keep water out.