Transmitting the Video

When choosing a transmission medium, test, try and test again.

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.

Need More Fiber?
We didn’t adopt fiber into the security industry until the late ’70s. Fiber optics is in my opinion the best cabling system we have today; it’s extremely stable, affordable and expandable. Fiber comes in two types: multimode and single mode. Despite its name, single-mode fiber is the most common for multipurpose CCTV applications.

The beauty of fiber is that it can be used for analog and digital signals alike. A single fiber can be used to transmit up to 64 high-definition, 30 fps, bi-directional analog video signals at a time. Not only that, fiber can be used for analog and digital signals simultaneously. A single fiber can easily be converted into a 1GB network. However, all good things have a limit, and you must stay realistic. A 1GB fiber network has a 60% load factor. This means you have the potential for about 600MB of bandwidth to work with. That’s still one heck of a lot of video transmission work in today’s market.

The best part about fiber is that distance, although still a factor, is no problem in most CCTV applications. You can transmit signals up to 40 miles with an off-the-shelf system.

Do you need training and special tools to work with fiber optics? Absolutely. However, the cost and the training required to competently design, install and/or troubleshoot a fiber system have become extremely realistic over the past 10 years. I remember my first fiber optic meter. It worked on 16 AA batteries—you can imagine the weight. I had approximately 30 minutes of field time to test my cables. The best part was the cost: $1,200. Today, a good fiber meter works with a 9-volt battery, gives you about 24 hours of field time, weighs in at a few ounces and costs less than $300.

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