This article will show different techniques for wiring CCTV cameras and video surveillance systems using spools of RG59 Siamese coax cable. It’s very important to purchase the right type and quality of the coaxial cable. A good and certified coaxial cable will provide a high-quality picture and is the foundation for a reliable CCTV system.
Not all coaxial cables should be used for CCTV camera installations. Be sure to read the specs before you buy. This guide applies to security cameras that use coaxial cables 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 a type of transmission line, used to carry high-frequency electrical signals with low losses. It has an inner conductor surrounded by an insulating layer, surrounded by a conductive shielding. Also, they have an insulating outer jacket.
The key to the coaxial cable’s success has been its shielded design, which allows the cable’s copper core to transmit data quickly, without succumbing to electromagnetic interference or damage from environmental factors. The diagram below illustrates the construction of a typical cable. Electrical signal flows through the center conductor.
Parts of a coaxial cable (refer to the image above):
- conductor: copper-clad steel, used to transmit the signal.
- dielectric: polyethylene providing insulation.
- braid: metallic material that acts as a shield.
- plastic jacket:
The metallic shield (braid) protects the core conductor from any external interference. The dielectric insulator protects the metallic conductor from the braid and provides more stability to the cable.
When installing CCTV systems that use coaxial cabling, it’s important to choose cables that have almost-pure metallic conducting material (it’s recommended to be 95% copper core).
The distance that these cables run depends by the quality and the thickness of the cable. There are various types of coaxial cables that are optimized for different CCTV installations projects.
Types of coaxial cables
The three most common cable sizes are RG59, RG6 and RG11. RG stands for “radio guide.” The numbers of the various versions of RG cable refer to the diameter (59 meaning .059, and 6 meaning .06, etc.).
They are also called RF cables, which stand for “radio frequency”. Most non-industrial coaxial cable is now known as RG6. The RG cables used in homes should be 75-ohm impedance.
What is Siamese cable?
RG59 Siamese cable is a heavily shielded cable that contains RG59 coax cable for video and a pair of 18 gauge 2 conductor power wires in one jacket. In other words, you have two cables in one: one for the video signal and another one for the power, both attached together (like Siamese brothers, hence the name).
The advantage of using RG59 cable for CCTV in camera installation is that it is more durable than most pre-made camera cables and can be run over 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 coaxial 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 that 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 HD-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.
