The most common means of transmitting CCTV video signals is through the use of coaxial cables, also called ‘coax’ for short. The commonly recommended coax types is RG59/U and RG11/U as these cables are used predominantly in CCTV and video installations. The RG refers to ‘radio guide’ and is a term that is used when sending Radio Frequency ( RF ) signals down a coaxial cable. These 75 ohms coaxial cables though similar in many ways, each cable type has its own physical and electrical characteristics, which must be taken into consideration before ordering.

Each of these cable types has a center conductor surrounded by dielectric insulation material, which in turn is protected by a shield or braid to prevent against electromagnetic interference ( EMI ). The outer covering of the coax is referred to as the jacket. The coax two conductors are separated by a non-conductive or dielectric material. The outer conductor acts as a shield and helps to isolate the inner conductor from spurious electromagnetic interference. The outer conductor covering helps physically protect the conductors.

A word of advice here; use only high quality cable and be careful to match the cable to the environment. Solid core, bare copper conductor is best suited for video applications. Use only cable with pure copper stranding. Do not use copper plated steel stranding even though it may be less expensive than pure copper stranding because it does not transmit effectively in the frequency range used in CCTV applications.

The connector of choice for CCTV systems is the BNC connector. Basically, there are three methods of terminating the coaxial cable. They are the solder, twist on and crimp methods, with the crimp method being the most popular. As this method can be used on solid or stranded conductors and it provides a good mechanical and electrical connection. This method is quicker than the solder method and unlike the twist on method which the center conductor is cut into by the center pin on the connector. The twist on method has no mechanical or electrical crimp or solder connection, thus this method is the least reliable of the three methods.

In the average CCTV installation, with cable runs of 750 feet ( 225 meters ) or less RG59/U is a good choice. RG11/U is best used for installation requiring cable runs of to 1800 feet ( 545 meters ). Additional, an added option is to have armoured coaxial cables of the RG59/U and RG11/U cable types if desired. However, if the distance required is beyond 2000 feet ( 605 meters ), then it is best to use amplifiers or fibre optics cable instead.

Consult INSTRUMECH’S Sales or Technical departments on the best way to suit your CCTV installations needs.