newbie question about video noise

[adamk 0]

Hi all,

 

I'm far from a professional CCTV installer, but I pieced together a system with two Pelco Spectra IV 22x color cameras, feeding a PC with a Geovision GV-2008 card for a museum education research project. All is working as planned, except that I have more noise in the signal than I would like. I'm running 400' of Belden 1694a solid copper core RG-6 cable with Kings crimped connectors.

 

The noise does not seem to be caused by interference- it looks random, with no striping or herringbones, it's just color "snow." Also, there seems to be some color distortion. Very bright areas, especially white spots on a dark background have a prism-like look (rainbows, not solid white) One person who saw it called it "color ghosting" although I'm not so sure.

 

The cameras overlook an area with variable lighting, mostly lit by a huge skylight which can be somewhat dim on rainy winter days. Also, the floor that the cameras look at is painted black, which may trick the cameras into making the image brighter than it really should be. Lastly, the contrast is huge in some areas, with brightly lit exhibits against a dark background.

 

Since the cameras have 23x optical and 10x digital zoom, I've noticed one thing: the noise seems to grow with the zoom level. That is, the snow gets larger as the zoom increases-- at max zoom (264x) the color "snow" spots are huge. I know next to nothing about this stuff, but this leads me to think that the source of the noise is inside the cameras, not in the cabling- If the noise was from the length of the cable or badly installed connectors, I would think that the noise would be constant, no matter what the zoom level was. Am I thinking right?

 

I feel like I've somewhat been able to reduce the noise by limiting the automatic gain control, but this is at the expense of a slow shutter speed or a darker image.

 

Once last observation: the two cameras seem to have identical images, neither has more noise than the other.

 

My questions:

 

1) Should I worry about cable routing and connectors, or is this a problem with relatively low light, or another problem altogether?

 

2) Since we have CAT5e cable run to each camera already to control the PZT, is it worth trying to run the signal through one of the two other free pairs with a balun, either passive or active?

 

Thanks in advance for your help.

 

Adam

[UMDRanger 0]

Could you post a screen shot?

 

If not here, on a free site, and then post the link website [dot] com

[Lolo Wolf 0]

Are the distortion/noise issues being observed on the PC monitor only, have you tried a direct connection to a cctv/crt monitor, bypass the DVR card/puter, (wire in a stand alone controller if you have one) and observe the pic with direct input to a test monitor run all the functions. I would start by trying that first. Some of the issues you raised may be puter video card related. A good start to troubleshoot would be to first start at the source of your signal, isolate the signal direct to montitor,if that doesnt come back clean then then continue back to the DVR/puter and check for other failures, wire intergrity, connects, voltage issues firmware probs, cam settings etc.

[adamk 0]

Both good ideas. I'll take a screenshot when I'm next at the museum and post it here, or somewhere else if I'm not allowed to do that.

 

As for testing the signal at the source, it's a bit trickier- they're mounted 35 feet up, so getting to them requires borrowing a scissor lift, turning off the fire alarm and disabling the particle detectors, etc. I did test them on the workbench before mounting and saw none of this, however it was in a much better lit area without the high contrast situations that bring about the ghosting. Still, it's worth a test. next time I go up there I'll bring a camcorder and record directly from the camera.

 

Also, I did bypass the computer and watch directly from the monitor and saw the same thing. That eliminates the capture card/computer as a problem, but not the cables.

 

Thanks.

[ezCCTV 0]

Just to mention, when you are using the digital zoom on your PTZ, you will get a much worse image, then when using purely optical zoom (pixelation etc.)

[adamk 0]

Yep, that I can accept, but the noise is evident when using only the optical zoom- it's just magnified when going to digital.

[Lolo Wolf 0]

Did these problems occur at first install, or did they start recently, was the pic ever clean after original install? You mention some other sensors and related security gear near or around the cams, does the distortions occur with the sensors and related devices off? aside from cable and actual mechanical PTZ suspect probs (lens etc) perhaps there maybe some outside electrical issues causing probs....just a thought.

[adamk 0]

The problems occurred at initial install. As for electrical devices:

 

1) the particle detector beam transmitters and receivers are each 200 feet away.

2) The cameras and are about 10' from florescent lighting, but the lighting circuit isn't active during the day when we're recording.

3) This is a huge interactive science museum with literally hundreds of mostly powered exhibits, routing the cables was tough.

 

We chose to run the cables along the high warehouse ceiling rather than close to the ground to avoid electrical interference. Crossing a few conduits was unavoidable, but I've tried flipping various electrical breakers to see if I could get the noise to abate with no luck.

[Lolo Wolf 0]

Hello adamk, do you have access to another cam (doesnt have to be PTZ) and hook up to your DVR/puter on a vacant imput, see if you get any pic issues, also have you tried differnt configs on the PTZ such as aperture settings, are the two cams set up with identical setting in so far as detail etc. From what you are describing as random issues perhaps these cams are having problems with adjusting to difficult low light lighting, is there a D/N function.... what if any pic probs occur when the cams are in BW mode. Do the problems surface when the cams are in static mode with quality lighting.... Asking a lot of questions but trying to troubleshoot with a method. Are you using a LCD monitor for your visual? If you benched these cams with zero issues did you bench with the same DVR/puter and PWR supply (isolated) or was it done direct to a cctv monitor? I ask to try and isolate the pic probs to perhaps the signal imput to your DVR and related cable/connections. If the cams were benched using the same system that you are using now and there were no probs then, either your signal is being interfered with (cable runs) or cams itself are problematic with the setup/settings. You said that you did observe the problems with bypassing the puter/dvr..... seems to be you should revisit the cable and related connects as well the power supply (to cams) Aside from manufacturers defects, most PTZ/cam issues I encountered after install tend to be cable/pwr related. I always try to bench my cams with identical PWR supplies used for the install and always with a dedicated cctv monitor to insure a clean pic that wont come back to haunt later after cableing is in place making troubleshooting leading to the actual run itself or a defect within the cam.

[adamk 0]

Thanks Lolo for your help. I'll try to answer your questions to the best of my ability.

 

I did connect another camera to the computer input and saw none of these problems.

 

Both cameras have identical settings.

 

I've played a bit with aperture settings, shutter speed, AGC, etc. Lowering the AGC limit helped a bit- the noise diminished, but so did the picture level. Opening the aperture helped a bit too. Brighter areas seem to have slightly less noise, but it's still there.

 

There's no D/N function that I've found. Pelco also sells a 23X day/night model, but the Pelco rep felt it wasn't worth the extra money for our purposes. Our webcast studio has one and I feel the picture is cleaner, but it also has a shorter cable run and is connected to a professional broadcast monitor. Unfortunately I'm not able to connect that camera to our system to test it.

 

Not sure if the cameras have a B/W mode- I'll check and see next time I'm at the office.

 

I've seen the noise with an LCD, a CRT computer monitor, and a CRT CCTV monitor.

 

As for benching, I didn't do with the computer, as we hadn't purchased it yet. I connected the cameras to the CRT CCTV monitor, but with only a short patch cable. That was a mistake, I should have tried it with the full cable length. I used the same power supplies on the bench as are installed now.

 

One thing I didn't do is connect the ground terminal on the power supply to the ground terminal on the camera. I was told (perhaps mistakenly) that it wasn't important, and also I noticed that most power supplies have no ground terminal anyway. The power supplies are 28VAC, by the way, and mounted about 5 feet away from the camera itself.

 

One other thing that I wonder about- maybe my standards for signal quality are unreasonable. We may use some of the footage for presentation at research conferences so my goal is DVD quality. Maybe that's too much to expect? I'll try to get and post a screenshot soon.

 

Thanks again.[/i]

[Lolo Wolf 0]

Is this a Europe/UK install? If so the cam ground maybe required code, as well the PS can be bonded for safety (metal cam supply boxes should have a binding nut) Being a museum with public access, were you inspected? Always follow electrical codes in your vicinity to insure a safe legal install that wont bite you later in the event of a problem, liability, fire, insurance etc. Aside from this...revisit the cable/runs/connects also is there a Flicker switch within the PTZ menu, check and see if that is on/off. I hope you resolve these problems, perhaps your PELCO rep has info related to any know issues for that model cam, best of luck and health.

[adamk 0]

This is in the US. I appreciate the reminder about the safety and codes, but all is good. There's no ground for the 28V camera, but the 120V is grounded and all is well secured and installed by a professional rigger. Our operations manager (also a firefighter) inspected and approved everything we've done, so I feel good about it. Not sure what a flicker switch is, but I'll look for it and see if I can make things good with that. Also a good idea to call Pelco.

 

Thanks again- I'll post any new info or images once I capture them.

[Lolo Wolf 0]

I just reread your original post and noticed that you are using the belden 1694a, doesnt that have aluminum braid? I mostly use 59 but when needed 6 I use belden 5339X5 (outdoor rated) most of my work is in harsh element but they have others in their line for cctv such as the 9290 with copper braid, perhaps that is the ssource of your pic probs, when you did the original bench and had zero issues what was the cable....rg6 or 59...braid type, although at short distance the 6 aluminum may not have produced probs however with a longer run it very well could.

[adamk 0]

According to the spec sheet, it has 95% coverage tinned copper braid. Around that is aluminum tape, but that's okay, right?

 

Here's their spec sheet:

 

http://bwccat.belden.com/ecat/pdf/1694A.pdf

[Lolo Wolf 0]

I only use copper braid for cctv, here is a linfo link regarding cctv cable applications (from Pelco)ftp://www.pelco.com/ServiceBulletinsTechTips/TechTips/5973021.PDF I am not being definitive that this is the source of your pic probs but over the years Ive encountered lot of signal problems repairing and retro fit for clients that used aluminum braid type cable really suited for TV and other applications. 95%copper braid is the standard for cctv. If you browse this forum there is quite a lot of posts regarding reasons (tech notes etc) on the usage of proper cable and termination. If after all your troubleshooting as I stated prior....start at the source (signal) and means of travel (cable) very often pic probs are created within the path.....using proper cable and proper fittings will eliminate most visual defects.

[adamk 0]

But isn't this 95% copper braid? I thought that tinned copper braid was the same or better, was I misinformed about this?

[Lolo Wolf 0]

the alum foil would be acceptable when using (high percentage) 95% copper, not tinned prods, could create probs, the cable listed on Belden CCTV apps does not list your cable, travel over to their site and review the Belden standards for cctv apps they do have a 6 for cctv ..... who advised you to your cable slection?

[Lolo Wolf 0]

I think the the tinned 95% prod would be ok but without the foil, for your cctv app

[adamk 0]

Interesting. I'm curious, though- given the the tinned copper braid has relatively low resistance (2.8 ohms/1000 ft, as compared to 5 ohms/1000 for 5339X5 and 2 ohms/1000 for 9290) what's the problem with having additional aluminum shielding in addition? My very limited understanding is that the quality and material of the braid is important for two reasons- 1) to provide a ground with low resistance and 2) to shield from interference. From reading some stuff on the Coleman and Belden sites, they've said that the aluminum shield is unnecessary for low frequency CCTV, but never that it would be detrimental. Can you explain what the problem is with having it there, as long as there is also copper braid with sufficient coverage?

 

I never thought there would be so many important little details!

[Lolo Wolf 0]

I am sorry I cant follow up so quick, just now we are in a deep freeze and I gotta fetch some more logs for the wood burner, quickly from a install point of view during termination/crimp etc the outer shield can come into contact with the center conductor and Ive found that additional aluminum shield to be problematic with my compression fittings and have had clean results using approved cable for cctv per the manufacturer spec, others on this forum have used all kinds of cable even alum cable tv touting good results,the optional foil shield some claim to reduce RF interference I just stick to what works well for me, in so far as pic probs I still think you should revisit all the connects,look for any (mechnical)radical bends and (electrical)sources of induced interference work back from the cam itself and maybe run a temp, lay out a loose cable and see what kind of results you get, test with a piece of rg59 95% or 6 without foil.... over the years Ive found that nothing is set in stone, some apps work in certain enviorments while others dont...

[adamk 0]

That makes sense about the connectors- I'll try re-crimping them with a fresh set, and get someone to do it who has more practice than me or the person who did them before.

 

Thanks again for your help, Lolo. Very educational!

[adamk 0]

Out of curiosity, I sent an email to Belden tech support to see what they had to say about tinned vs. bare copper shield, and whether foil was a problem or not. Here's their response, FWIW:

 

Belden product 1694A would make the very best CCTV RG6 on planet

earth ! Tinned copper and bare copper on shield is 100% equal and actually tinned copper is slightly better because it will resist corrosion. The foil shield can only help , in no way hurt .

The noise is not do to the cable for sure , check your connections...make

sure the shield is not shorting against the conductor in any way , or maybe

interference from your power cable at the camera etc...again, 1694A would

be the absolute best RG6 attainable.

[Lolo Wolf 0]

Hello adamk, in so far as the corrosion aspects noted I agree and as stated prior the timmed 95% would be ok, however I still think you are better off without the foil and still think you should revisit all the inter/connects as well investigate any induced electrical interference, when refering to the foil for my own installs I find less problems terminating with the compression fittings that I use, it is very possible that you did not terminate your connects properly and indeed may be that the shield is contacting the conductor, my opinion on the shield to you was in regard for ease of install... by not having a optional shield less likelyhood of that occuring in the first place by a person who is new to terminating a cable. Sorry if you felt my advice was wrong

[adamk 0]

Lolo,

 

By no means did I think your advice was wrong! Apologies if it sounded that way. I know that you and many other people on this forum have a ton of real world experience, which of course I have next to none. It's just that I'm new to all this and looking at things from all angles, and was curious to hear what Belden had to say about this from a theoretical perspective. I was just trying to understand why the foil could be a problem, and I guess I didn't quite get what you were saying earlier about accidentally grounding the core, but that does make sense, and I'm going to find someone expert to recrimp the connectors. Again, thanks for all the time you've spent helping me troubleshoot this problem, and thanks for teaching me so much about this stuff. I'll definitely post updates to this thread.

 

Adam

[Lolo Wolf 0]

Adamk, you are correct in looking at all angles, in troubleshooting and for expanding your knowlege base for sure. No matter what high quality cable you use if it is not not terminated properly or run correctly problems will arise, without seeing the pic/visual prob it is harder to determine the cause but I tried to walk you through a method of steps and trial in differnt configs without using more advanced cable testing to eliminate some basic known issues such as power related and connects, Ive found that most probs with poor pic with known properly running equip is due to the actual mechanical failure of electrical apps such as cable runs (placement), HV and LV power issues, the use of failed splices,etc... .. the list goes on. With my installs I always work with a approved plan, I review the layout, if possible get a asbuilt and look for any code violations or unsafe work that may hamper my job... some folks go with a plug and play attitude. You did well to bench your cams and that gave you zero issues, however did you test/bench the cams in similar lighting conditions that you encountered on site, if so then really unless there has been a dual failure within both cams at the same time (which I doubt) then it leads me to think that your problem has something to do with the hardwired cables. Perhaps when you installed the cables maybe radical bends, or damaged when attached outside wall/no conduit(hanger/clips/ damage to the jacket/short etc) there are many varibles to visit finding the cause. Most of the call backs Ive had are due to either acts of God or tampering, or after the fact improper electrical device installs that have stepped on my work. I too learn each day as much as I can with life in general, anybody who thinks they know it all is a fool or never been in the real world hands on in the field. Regards