Long Coaxial Siamese and Unshielded Twisted Pair cables are the main cause of picture quality loss on CCTV systems. Regardless how sharp the picture a security camera can produce or the quality of the Monitor, the cables connecting them can cause attenuation and picture distortion. This information describes exactly how to overcome this cable surveillance CCTV limitation performance and how to eliminate conditions that will affect the picture quality.
MEASURE OF PICTURE QUALITY in Surveillance Systems
One way to measure picture quality is to check how fine a detail may be observed in a picture.
CCTV Cameras and Monitors are often specified by the number of “Lines” that they can generate and display. The greater the numbers of “Lines”, the finer the picture is. On any given security system the Camera and the DVR should have similar “Lines” capability.
Recorders must also be able to record and play back at least an equal number of “Lines” as the security camera and monitor.
One measure of picture quality loss, is when more than ½ of the energy that transmitted into the cable is lost. Thus at the cable length that ½ the energy at the desired quality level is lost, that defines the maximum length of cable that can transmit that level of quality. This leads to the following limits for maximum cable length at given picture quality levels.
||RG59/U COAX||UTP PAIR|
|330TVL||650 Feet||280 Feet|
|400TVL||600 Feet||250 Feet|
|470TVL||550 Feet||230 Feet|
|570TVL||530 Feet||200 Feet|
**YOU CAN INCREASE CABLE LENGTH WITHOUT QUALITY LOSS Both Coaxial and UTP cables can be extended far beyond the limits shown by amplifying and equalizing the signal with signal amplifier.