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Security Technology Executive
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Transmitting the Video
When choosing a transmission medium, test, try and test again.The Latest from SIW
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By Charlie R. Pierce
Security Technology & Design
Transmitting the video signal from point A to point B was the very thing that gave the CCTV industry its name. We had, for the first time, a closed circuit between the camera and the monitor—a direct, private connection. Coaxial cable was the carrier. When you consider that this method of transmission has given us more than 50 years of dedicated service, you have to be impressed. However, as with everything technical, innovation has driven us past cable and into the new world.
Today, we transmit via coaxial cable, fiber optics, twisted pair (two wire, Category 3, POT lines, Category 5), wireless (RF, microwave, WiFi, FM) and satellite signals. It is not uncommon to find our more sophisticated systems using a combination of two or more transmission methods. The idea of a closed circuit has now taken a back seat, so we’re eventually going to have to stop calling it CCTV.
Coax Mistakes
Coaxial cable is still the most misapplied and improperly installed form of video transmission in the market. There are several mistakes I still see people regularly make.
Mistake 1: Trying to save money by using cheap cable or non-copper cable. The dictates are really simple. Use a cable that has a braided copper shield, a 75∑ impedance dielectric, and a solid or stranded copper center core with a jacket that meets the requirements of the environment.
Mistake 2: Overrunning the cable length. Different types of coaxial cable have different run lengths. RG-59/U is the most common type of coax, and it can be used on runs of 750 feet or less. RG-6/U is good for up to 1,200 feet, and RG-11/U can be stretched out to almost 3,000 feet. These limits shouldn’t be pushed.
Mistake 3: Wrong connections. Even though we standardized on the BNC connector some 30 years ago, I still see folks insisting on using F connectors, UHF connectors and RCA connectors, with every negative result in the book. Stand back and scratch your head. Why can’t you get a clean picture? Because you tried to cheat.
The three biggest downfalls of coaxial cable have always been its bandwidth, distance restrictions and susceptibility to outside interference from RF and electrical magnetic induction (EMI). The newest problem with coaxial cable is that it cannot carry digital transmissions at the levels and bandwidth we need. So coax is on the way out.
