Problem With Security Cameras Displaying Scrolling Lines and Dots

by Gireesh
(Trivandrum, Kerala, India)

Question:


I have installed 16 cameras in a plastic manufacturing factory. A few of the camera's are showing disturbance in signals like signal issues in TV channels. There are scrolling dots or lines in the screen.

Lots of heavy machines are running 24 hours in the factory. I used RG59/U coax cable and the maximum length used is 170 meters. (approx 558 feet)

How can we reduce the noise in the video signals?

Answer:

This is a great question Gireesh and a common problem with analog CCTV systems.

Your distance is not problem with the RG59 coax cable. You can get up to about 800 feet with that.

Here is the most likely issue you are having.

Electromagnetic Interference (EMI). EMI can come from electrical wires or machinery and can ruin the video image being transferred through the coax cable.

You need to trace back all of your coax cable and see where it comes close to any machinery or high power electrical lines to find the source of the problem.

The next thing is to create space if possible between the coax and the problem. Or you can also use UTP.

UTP stands for Unshielded Twisted Pair. It is your basic category 2 to category 6 wire cable used for phones and networks. What happens is the video is converted on a 100-ohm balanced 24 gauge network type cable (Cat 2 to 6) unshielded to a 75-ohm unbalanced video signal. You have to use a device to convert the signal called a balun. A balun could be passive or active. An active balun will allow you a much greater distance for the video signal.

The advantage for using UTP is that it has noise immunity. Meaning you will not have to worry about any EMI interference like you do with coax cable. You can get around 1000 ft distance of video signal with a passive system (6000 ft or more with an active system).

Hope that helps.

Peter Brissette
Video Expert



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