Cat5 or Siamese Coax
I have experienced a number of clients that ask about using cat5e cable rather than traditional Siamese coax cable for their camera runs. Is cat5 heavy enough? Will I be able to transmit video as far as I can with Siamese? How does the power work with regards to cat5 cabling? These are all very good questions and we will look at each in turn.
-First, Is cat5 heavy enough? and similarly, will I be able to transmit video as far as I can with Siamese?
The short answer is yes, cat5 is heavy enough to transmit video. In fact, most sources show that the 24AWG (American Wire Gauge) used to make up the cat5 will actually transmit video farther than the RG59 used in the Siamese cable. One only needs to incorporate an adapter from cctv BNC connectors to unshielded twisted pair (UTP) to make this physical connection work. Such an adapter in the CCTV business is referred to as a balun, and comes in several different models – Learn more about Baluns and BNC connectors.
-Next, How does the power work with regards to cat5 cabling?
This is the part that needs special attention. When using cat5 for power transmission, I always recommend using 24VAC or dual voltage cameras, in order to not starve or under-power the cameras. This is done by incorporating two (2) of the twisted pairs in the cat5. So essentially, you will have one (1) of the twisted pair being used for video and two (2) of the other twisted pairs used for the power, leaving you with one (1) unused twisted pair in the cat5. (I have seen all-in-one adapters that allow DIY installers to plug in a finished cat5 (RJ-45) connection on both ends and accomplish both video and power portions, though distance is usually a limiting factor.)
So if you or your clients have some extra cat5 lying around, go ahead and give it a try. It wasn’t mentioned earlier, but even your back will thank you, as cat5 is considerably easier to carry around and pull through conduit!
Wire Gauge and Voltage Drop
For the majority of analog cameras, Siamese cable is adequate to run both the power and the video. The most common type of CCTV Siamese cable is a combination of RG59 coax and 18/2 power cable. RG59 will carry the video signal around 750 ft, so for most runs that will be more than enough. Power is what will restrict most longer runs.
18/2 cable is two 18 gauge wires. That is simple enough; if there were four wires it would be called 18/4. Like shotgun shells and needles, wire thickness is measured by gauge and the smaller the gauge the thicker the wire. So, 14 gauge wire will be thicker than 18 or 24 gauge wire. The reason that is important is that a thicker wire will transmit electricity farther that a thinner wire. Why does this matter? Because if you have a long run from the power supply and DVR to a camera and there is no way to power the camera locally, you will have to adjust the gauge of the wire to compensate for the voltage drop – View our voltage/amperage quick guide.
Below we’ve created a chart that will help with planning a long run. Make sure when calculating that you know the voltage and amperage used by the camera. Make sure you use the max amps listed on the spec sheet (here’s an example where we talk about amps and power along with other important features to look for on a spec sheet).
If you have a question or comment about CCTV power supplies or cables, we welcome comments below!
Max Power Distance Chart
(Quick chart based on a 10% voltage drop from power source to device)
Embed the Max Power Cable Distance Chart on your site