Ground loop or noise due to EMI

[bokarinho]

Hello and greetings to all,

Recently i installed a Dahua DVR (XVR5116HS-I3) with Dahua Cameras (Dahua HAC-HDW1509T-A-LED-S2) and for some cameras i am getting horizontial lines that tremble on my output. I have used Dahua U/UTP Cat.5e Cable with Dahua Passive balun. I have a central power supply with enough power to feed more than 16 cameras. Each camera gets power and transmits signal in its own UTP cable (orange(+) / orangewhite(-) for balun and for power brown/green stripped together(+) whitebrown/whitegreen stripped together(-)). I have grounded my DVR to the same point as my PSU AC ground point (i have run a cable from my DVR's earth screw to the PSU ground in the AC terminals). What seems to eliminate the problem, is using a separate PSU next to the the camera. Is it a ground loop problem, is it EMI or maybe not enough voltage reaching the camera? But this happens to cameras that are relative close to my central PSU.
Should i get rid of cat5e UTP cable and run RG59 with 2 additional cables for power?
Please a piece of advice here...

 

[steve1225]

Why You bought and installed analog system using passive converters?
You have CAT5 cables to cams - You should buy IP cams / NVR..

This asking for all the problems that come with outdated analog technology?

Analog installations are very prone to RF magnetic / electrical interference..
They require very good RF shielding on cables and good isolated power sources.
Cables should not cross with other cables (like electric ones). They should be put in separate conduits..

Classic RF coaxial cable have shielding, but CAT5e cable don't..
CAT7 cables are full shielded (each pair have own shield). They are very thick and not easy to install.. They require grounding on one of the sides...

 

[bigredfish]

More often than not when I was using analog/HDCVI equipment the problem you describe was from the power supply. I never had much luck with central power supplies.

To test, simply use a single power supply/wall wart for that one camera on a different outlet. 99% of the time that will resolve the image scrolling. Of course it’s messy but I ended up with separate power adapters for each camera plugged into a multi outlet and no more problem.

 

[TonyR]

Wow...what a choice: Pull 16 RG-59 coax cables plus power cables or replace 16 cameras with compatible IP cameras (specs say that XVR will support 16 IP cameras).

Do the lines appear when viewing all 16 cams or just some?

 

[bokarinho]

Yeah you may be right in a matter of speaking, but one factor is always the cost and IP cameras cost even more, NVRs cost more, PoE switches may solve a lot of problems but they cost more and i was searching for a modest (considering money) solution.

@bigredfish: Yes using a separate PSU to another wall outlet, specific for the camera with the problem eliminates the problem. But i want a cetral solution as i am not in the mood to bring AC power sockets nearby each camera. What i am going to do is to use another Cat5e cable or 2x0,75mm^2 cable for the power, so not to pass video and power signal through the same cable. This will double my work but i must get the results. Replacing the cameras is not an option for the moment, but i have spare Cat5e that i will use as i stated before. Hoping that it will work (2 UTP cables for the problematic cameras).

 

[bokarinho]

Do pair selection matters? For example using the blue/bluewhite for balun +/- instead of using for example orange/orangewhite will make any difference. I assume that all pairs are equal, but somewhere i read that they have diffirent resistance, but i may be wrong.

 

[bigredfish]

No

I never cared about colored pairs. I simply made sure I was using the same colors on both ends!

typically I would use 2 pair for power and one pair for video. The “spare pair” I would occasionally use for a low wattage IR Illuminator

 

[bigredfish]

Yeah you may be right in a matter of speaking, but one factor is always the cost and IP cameras cost even more, NVRs cost more, PoE switches may solve a lot of problems but they cost more and i was searching for a modest (considering money) solution.

@bigredfish: Yes using a separate PSU to another wall outlet, specific for the camera with the problem eliminates the problem. But i want a cetral solution as i am not in the mood to bring AC power sockets nearby each camera. …

Thought so

Again messy but cheap and easy. The power adapters all get plugged into a single multi outlet strip at the NVR, not at each camera

 

[tigerwillow1]

Do pair selection matters?

My shoot from the hip opinion says probably not, but with each pair having a different twist rate, you could have some sort of edge situation where the wire length or twist rate makes a difference. Only way to find out is to experiment.