Don’t Cut the Cord on Coaxial Cable Just Yet

Sure, technicians are becoming more and more familiar with IP technology. But coaxial cabling is still prevalent in several applications.

HAVE YOU EVER WORKED with a radio guide? You probably have and may have not even realized it. If I told you that the term radio guide can also be represented by the abbreviation RG and is often used to identify coaxial cable, such as the popular RG-59, then you may now know what I am talking about. But do you really understand this cabling oddity?

As I start discussing coaxial cabling some readers are undoubtedly saying, “Why is he talking about this ancient technology? Everyone knows that today’s cameras are all IP based and typically transmit on category cable such as Category-5 or -6.”

While that statement to some extent is true and many of today’s technicians are becoming more familiar with IP technology, coaxial cabling is still used in several applications including CCTV systems. In fact, according to the latest statistics on “Most Popular Video Surveillance Transmission Methods” (SSI Gold Book, December 2015) coaxial cable is still deployed 31% of the time in video systems. So this dinosaur is not extinct yet – and we have to know how to properly work with it.

If you do not understand the physical and electrical characteristics [of coax], you can produce some really serious performance issues and unhappy customers.

One thing veteran installers can tell you about working with coaxial cable is if you do not understand the physical and electrical characteristics, you can produce some really serious performance issues and unhappy customers. Let’s all take this warning from the pros and take a moment to review these particulars about coaxial cable. If nothing else, you may want to take the advice of the well-respected video products manufacturer Pelco, which notes, “Many of the common video problems with picture quality can be avoided by selecting the proper transmission media and following proper installation techniques and procedures.”

Coaxial cable or ‘coax’ can actually be thought of as a radio antenna enclosed in a metallic shield. The center conductor is the antenna, which is surrounded by a dielectric and then an outer conductor or shield. It is constructed in such a way to provide protection from outside signal interference. When installing and handling coax, one should be very careful not to kink when bending or avoid crimping when stapling as this can impede signal transmission. Make sure to use the right tools for this work (see Tool Tip below).


Next: The Difference Between RG-58 and RG-59


Deconstructing Coax Cable Considerations
There are three important characteristics to look for when selecting coaxial cable. The first is the impedance of the cable. An example would be that RG-58 coax is 50 ohms and used for two-way radio systems or antennas on wireless security equipment. On the other hand, the popular RG-59 coax is 75 ohms and is used on systems such as CCTV and CATV. The next item to consider is the center conductor type, such as solid bare copper for CCTV or solid bare copper/copper-covered steel for CATV. Use larger gauges for longer distances. Another tip: Use stranded bare copper for CCTV pan/tilt/zoom (p/t/z) applications to prevent breaking.

The last consideration is the appropriate outer conductor shield. For CCTV it should be 95% bare copper braid and for CATV it should be 65%-95% aluminum braid plus one or more aluminum shields. With recent copper metal cost increases there has been temptation to substitute cheaper steel and aluminum constructed coax for solid copper. This can cause transmission attenuation and problems such as ghosting of images in CCTV systems. Avoid the temptation.

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Anixter offers a variety of handy installation tools from manufacturers such as Belden, Corning, Jonard, Klein, Ideal Industries, Siemon and more.

TOOL TIP
We have seen how special coax cables are in providing good RF transmission. This is why I have selected some of the special tools as supplied by distributor Anixter for the perfect installation. Look for many under the “Cable Preparation Tools” label within Anixter’s “Hardware and Supplies” category online. Shown to the left are a coax stripper, a connector compression tool and compression connectors.

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About the Author

Bob Dolph
Contact:

Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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