Cable Guide

The choice of a particular coaxial cable depends on the environment in which it will be used and the electrical caracteristics required. By far the most common coaxial cables are the RG59/U and RG11/U, having a 75-ohm impedance. For short camera-to-monitor distances (a few hundred feet), preassembled lengths of RG59/U with BNC connectors at each end are used. Preassembled lengths of 3, 25, 50, and 100 feet are available. Long cable runs (several hundred feet and longer) require higher quality cable such as RG11/U. Runs of several thousand feet, particularly between several buildings or if electrical intereference is present, may require fiber optic cable. When the camera and monitoring equipment are in two different buildings, and likely at different ground potentials, an unwanted signal may be impressed on the video signal, which shows up as an interference (wide bars on the video screen) and makes the picture unacceptable. The chart above summarizes the transmission properties of coaxial cables when used to transmit the CCTV signal.