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Cable connectors

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector (see diagram below). Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather than screw onto the cable, but the best to use are the one that compress onto the cable giving you a strong water tight seal. Compression connectors are also easy to instal remove most of teh hassels and attenuation which comes from poorly installed crimp connectors.


CCTV Video Cable Installation Tips

1. Use solid core co-axial cable only, not stranded cable. The solid core must have a copper core with copper shield



2. Avoid high voltage cable. A good rule to follow is: for every 100 volts there should be a separation of 1ft between the video cable and power cable.



3. While cabling, avoid areas like electrical equipment or transmitter rooms etc., where EMI interference is expected. This can create all types of interference to the video picture. Co-axial cable is very easily prone to EMI.



4. Minimize cable breaks - Every extra connection in the cable can deteriorate the quality of the video signal. If unavoidable, make sure the insulation is good; otherwise over time the exposed cable can touch the ground causing ground loop currents. It may be difficult or expensive to fix such problems in the future.



5. Avoid sharp bends, which affects the cable impedance causing picture reflection and distortion. This is especially true while getting all the cable into the CCTV monitor rack.



6. Poor BNC connections are the major cause of poor picture quality. Also BNC connectors should be replaced every couple of years and should be part of the system maintenance program. We recommend compression style BNC connectors which are working their way into the market as a main stay for calbe installation. The Compression style connectors provdie a weatherproof seal and if the cable gets pulled on they don't let go of the cable.



7. Use metal conduits for high security applications.



8. Use UV resistant or Direct burial cable for outdoor applications providing better protection against the elements.

Video signals used in CCTV systems must be transmitted over 75 ohm 'low-loss' coaxial cable in order to give acceptable picture quality at the receiving end.

The use of co-axial cable prevents interference to the quite small (1v peak to peak) video signal from external sources and because the cable is low in capacitance then the high frequency elements of the signal are not attenuated to the same degree as would be the case with say a standard twisted-pair type transmission cable.

Distance limitations do have to be set for different types of coaxial cable but these are subjective since different end-users will accept different levels of picture quality and hence levels of signal attenuation.

'Acceptable' pictures should be obtainable over the distances as shown for the following common types of cable used in the CCTV industry:


• Standard un-screened 4 core alarm cable - 5-10m (single camera only)


• Composite video cable: 100m (328 ft)


• URM70 - 200m (656 ft)


• RG59 - 200m (656 ft)


• CT100 - 350m (1148 ft)


• CT125 - 450m (1476 ft)


• CT167 - 750m (2460 ft)



Different grades within each type of cable exist. These grades define the use to which the cable can be put. ie suitable for direct burial etc. The type (ie URM7O) defines the electrical performance.

Note: that the above distances quoted assume a continuous cable run with a minimum number of joints.

Some important points


1. Every well-made joint will add extra signal attenuation equal to approximately 50m of cable, badly made joints considerably more!
2. Coaxial cable is generally supplied either on 500 or 1000' spools. Always remember that a video signal is only 1 volt in amplitude and is thus very vulnerable to external interference and losses in poor quality cables.
3. Never use aerial down lead type coaxial cable for CCTV signals!
4. Always keep video signal cables as far away as possible from mains cables and wiring that may carry high-frequency signals.

When running cable, it is best to follow a few simple rules:


1. For any Runs over 100ft, select Bulk Cable. You will need 2 connectors per cable run.
   For any Runs under 100ft you may select the Plug and Play cables with Connectors but a RG59 Siamese (video / power) combo cable is recommended.
   
2. Always use more cable than you need. Leave plenty of slack
3. Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later
4. Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference
5. If it is necessary to run cable across the floor, cover the cable with cable protectors
6. Label both ends of each cable
7. Use cable ties (not tape) to keep cables in the same location together