This article will show different techniques for wiring CCTV cameras and video surveillance systems using spools of RG59 Siamese coax cable. When you are about to design a HD analog CCTV project it’s crucial to know which CCTV coaxial cables can be used and how they affect the overall quality of the system that will be installed.
Not all coaxial cable should be used for CCTV camera installations. Be sure to read the specs before you buy. This guide applies to security cameras that use coax cable to transmit video to DVRs and monitors. This includes analog CCTV cameras and the following HD security camera types: HD-TVI, AHD, HD-SDI, HD-CVI.
The construction of a coaxial cable
A coaxial cable is constructed to allow the transmission of the signals and at the same time protect against external electromagnetic interference. In the image below we can see the parts of a coaxial cable: conductor (used for transmission), dielectric (insulation material), braid (acts as a shield), outer jacket (protects the cable).
When a camera is connected using a coaxial cable to a monitor or recorder, the braid is used to protect the center conductor from external interference. The dielectric is used to insulate the center conductor from the braid and the outer jacket is designed to protect the cable. Due to this need for protection of the coaxial cables for CCTV we must use quality material such as conductors with a higher percentage of braid (95% is a good example). The distance from the installation of a camera is directly affected by the quality and thickness (gauge) of the coaxial cable used.
What is Siamese coax cable?
RG59 Siamese cable is a heavily shielded cable which contains RG59 COAX cable for video and pair of 18 gauge 2 conductor power wires in one jacket. The advantages to using RG59 cable for CCTV camera installation is that it is more durable than most pre-made camera cables and can be run in long distances without interference. You can also cut each cable run to the exact length that you need which makes the cabling part of the installation neat.
The above picture shows a close-up of RG59 cable. You can see the 18 gauge power cable and RG59 coax portions of the cable clearly.
RG59 siamese cable comes in 500 and 1000 foot spools. White and black cable is typically available in case your cable is visually exposed and you have a preference in color.
What coaxial cable to buy for my CCTV system?
This is what you need to know. Be sure to select RG59 cable with a solid copper core / inner conductor and 95% copper braiding. Look at the specification in the below image. These two elements are highlighted and the arrows point to the parts of the cable they refer to. The impedance of CCTV cameras is 75 ohms. In order to have minimum video loss, you should use coax cable that also has an impedance of 75 ohms. Coax cable is also available in 50 ohm and 93 ohm. Do not use these for CCTV installation. Use ONLY 75 ohm cable.
What about Cable for HD CCTV (AHD, TVI, CVI)?
RG6 can also be used for CCTV. It is also available with a solid copper core / inner conductor and 95% copper braiding. RG6 can be run farther distances than RG59 without video loss, however, RG6 is a thicker, more rigid cable which is not as convenient to work with (especially around corners). RG59 is rated at 700 feet and RG6 is rated at 1000 feet for analog CCTV. RG59 is more typically used.
HD CCTV technologies such as HD-CVI cameras, AHD cameras and TVI cameras also operate at low frequency – similar to analog CCTV. You should use RG59 or RG6 with a solid copper core and 95% braided shielding for HD security camera installations. These systems, known as “HD over coax” us the same cable as traditional analog CCTV, however high quality cable for these systems is even more important because of the higher bandwidth requirements of the video.
What about cable for 3 Megapixel, 5 Megapixel, and 4K resolution?
The technology for “HD over coax” security camera systems continues to improve. 3 megapixel, 4 megapixel, 5 megapixel, and even 4K HD CCTV cameras are available. HD over coax DVRs that support these resolutions are also now available. If you wire your system with high quality RG59 coax cable now, it will be ready to upgrade to any of these camera types in the future.