CCTV Cable Installation: Coax, Siamese and BNC for a DVR System

CCTV cable installation for a classic DVR system comes down to three things: run one siamese cable (coax for video bundled with a two-core power pair) from the recorder to each camera, terminate the coax with a BNC plug and the power pair with a DC plug, and keep every run away from mains cables. Many picture problems on wired analog systems later turn out to be a loose BNC, too little voltage at the far end of a long power run, or a video cable laid next to mains wiring.

This guide covers the coax side of wired camera installation. If your cameras use a single network cable for both data and power instead, that is a different system, and the PoE camera setup guide is the one to follow.

First: confirm you actually have a coax system

Before buying any cable for CCTV installation, check what your cameras and recorder expect. The two wired systems look similar on a shelf but are not interchangeable.

1. Look at the camera's tail. A coax camera usually has a round BNC socket for video and a small barrel socket for low-voltage DC power (often 12V, but check the label). A network camera has an RJ45 (network) socket, sometimes with a DC socket as well.
2. Look at the back of the recorder. A DVR for coax cameras has a row of round BNC inputs, one per camera. An NVR has network ports instead, or none at all if the cameras reach it over your router.
3. Read the labels. The camera label and the recorder manual state the video format and power requirement. Some recorders are "hybrid" and accept both kinds, but only on certain channels, so check which.

If you have network cameras, stop here and use the PoE guide. Everything below assumes coax cameras and a DVR.

Choose the right cable

Siamese cable: video and power in one jacket

Siamese cable is coax and a two-core power cable moulded side by side, so one pull gives you both. For most home and small-shop installs it is the simplest choice. The alternatives are separate coax and power cables pulled together, or a pair of adaptors (called baluns) that send video, and on some types power, over network cable, which is useful when network cable is already in the wall.

What to check when buying:

• Solid copper centre conductor. Cheaper coax sometimes uses a steel core coated with copper. It may look fine on a short run, but picture quality falls off sooner on longer ones.
• A decent braid or shield. The shield is what keeps electrical noise out of the video. A thin, sparse braid lets interference in.
• Thick enough power cores. Thin power cores cause the voltage drop problem described below. Thicker is better on long runs.
• Outdoor-rated jacket for anything outside. Indoor jackets crack in sun and rain over time. Use cable sold for outdoor or direct-burial use where the run is exposed, or put it in conduit.

The common thin and thick coax grades both work for short runs. The thicker grade usually carries video further before the picture softens. The usable distance depends on the cable, the camera and the recorder, so check the recorder and camera manuals rather than relying on a single figure from a forum.

Connectors you will need

• BNC plugs for each end of the coax. Compression-type BNC plugs, fitted with the matching tool, are the most reliable. Twist-on plugs are quick but tend to work loose. Crimp plugs are fine if you have the right crimper.
• DC plugs for the camera end of the power pair. Screw-terminal DC plugs need no soldering. Check which way round the camera wants the positive and negative.
• A power supply. Either a single power supply box with one output per camera (fused per channel is better), or one plug-in adaptor per camera near the recorder.

Plan the runs before you drill

A few minutes with a sketch saves a lot of rework.

1. Mark each camera position and the recorder position. Put the recorder somewhere cool, dry and hard for an intruder to reach, with a router and power socket nearby.
2. Measure each run along the route the cable will really take, including up walls, across ceilings and around corners, then add slack at both ends for a service loop.
3. Map where mains cables run. Note light switches, sockets, ceiling lights and the route from the distribution board. Your video cable should cross mains wiring at right angles where it must cross, and otherwise keep a clear gap from it.
4. Decide where each cable enters the building. Plan for a downward drip loop just before each entry point so rainwater runs off the cable instead of into the hole.
5. Label both ends of every cable with the camera name before you pull it. Matching unlabelled cables later is slow and error-prone.

Voltage drop on long 12V runs

Most coax cameras run on low-voltage DC, typically 12V, and at low voltage even a modest loss along a long, thin cable can leave the camera short of what it needs. The camera may still power up but behave strangely, and the problem often shows up only at night, when the infrared lights switch on and the camera draws more current.

A worked example to show the idea, not a rule: suppose a camera needs 12V and your supply delivers 12V at the box. If the run is long and the power cores thin, the camera might receive noticeably less once the infrared lights come on. Whether that is enough depends on the camera's tolerance, so check its label or manual for the accepted input range.

Ways to deal with it:

• Use thicker power cores for the long runs.
• Power the far camera locally from an outdoor socket installed by a qualified electrician and a weatherproof supply, instead of sending 12V down the whole run.
• Measure. With the camera running and its infrared on (cover the lens or test after dark), measure the voltage at the camera's DC plug with a multimeter. If it is below the range on the label, the cable or supply needs changing.
• Do not simply turn up the voltage. Some supplies have an adjustment screw. Raising it to compensate for a long run can over-volt cameras on short runs sharing the same supply.

Step-by-step wired camera installation

Step 1 — Bench test before any cable goes in

Connect each camera to the DVR with a short cable on the floor or a table, power it, and confirm a picture on the recorder's monitor. Set up the recorder, the date and time, the recording schedule and the hard drive. A dead camera is far easier to spot now than after it is on a wall.

Step 2 — Pull the cable

Switch off power at the distribution board before drilling near any wiring, and use a cable detector before drilling walls. Pull cable gently. Kinks and tight bends damage coax, and a cable crushed under a clip or a staple can cause a lined or snowy picture months later. Use cable clips sized for the cable, not staples driven through it. For ladder or roof work, have a second person hold the ladder, and do not work at height alone.

Step 3 — Terminate the ends

Strip the coax to the dimensions the BNC plug maker gives, fold the braid back neatly, and make sure no braid strand touches the centre conductor. Fit the plug and give it a firm tug test. Then fit the DC plug to the power pair, checking polarity against the camera's marking. A reversed DC plug can damage some cameras, so double-check before connecting.

Step 4 — Test each run before mounting

Plug the camera in at the wall position, still in your hand, and check the picture on the DVR. Wiggle the BNC at each end. If the picture flickers or drops, re-terminate that end now.

Step 5 — Mount, seal and tidy

Mount the camera, aim it, and seal the outdoor joints. Outdoor BNC and DC joints should sit inside a weatherproof junction box, or at least be wrapped with self-amalgamating tape, and positioned so water drips away from them. Water in a BNC joint is a common cause of a picture that fades or goes noisy over time.

Step 6 — Connect the recorder to your network

Plug the DVR into your router with a network cable and set up remote viewing as the recorder's manual describes. Whether a particular DVR can be added to the Yoosee app depends on the recorder model and firmware, so check the recorder's documentation or ask the seller before assuming. Decide also where footage should live: the comparison in NVR or SD card for a wireless camera explains the trade-offs between central recording and per-camera storage, and the same reasoning applies to a DVR.

Step 7 — Check again after dark

Look at every camera at night. Night is when infrared draws the most power and when weak cable runs show themselves as rebooting, flickering or a black picture.

What each symptom usually means

• Rolling horizontal bars or a hum pattern across the picture. Usually interference from mains wiring running alongside the coax, or a ground loop between equipment powered from different sockets. Re-route the cable away from mains, or try powering the camera and recorder from the same circuit. A ground loop isolator on the coax can help.
• Picture fine by day, reboots or goes black at night. Usually voltage drop on the power run once the infrared switches on. Measure at the camera and see the voltage section above.
• Snowy, soft or washed-out picture on one camera only. A long run near its limit, poor cable, a damaged section, or water in a joint. Swap in a short test cable at the camera position to confirm.
• "No video" or "video loss" on one channel. A loose or badly fitted BNC, a broken centre conductor, or no power at the camera. Check the DC plug first, then the BNC at both ends. The article on no video on a CCTV camera covers black live views in more depth.
• Every camera down at once. Usually the shared power supply or the recorder, not the cables. Check the supply's output and fuses.

If the symptom does not fit any of these, the broader security camera not working guide works through problems in order, starting with what you can see.

When to get help

Call a qualified electrician if you need a new outdoor socket, need to run cable near or through the distribution board, or are unsure whether a route is safe to drill. Get professional help for long roof or high-wall runs if you are not comfortable at height. And if a camera still misbehaves after you have swapped in a short known-good cable and a known-good power adaptor, the camera itself may be faulty: contact the seller with the steps you have already tried.

Install or resell cameras?

On coax jobs, call-backs are often caused by terminations and power rather than the cameras themselves. Fit compression BNC plugs with the proper tool rather than twist-on ones, and do a tug test on every end. Measure voltage at the furthest camera with its infrared running before you leave site, and note the reading on the job sheet. Label every cable at both ends, leave a short service loop at each camera, and put outdoor joints in a junction box so the next visit is a quick check rather than a hunt. If you install or sell security cameras and want to discuss supply and dealer terms, see the Yoosee partner information.

Frequently asked questions

Can I use network cable instead of coax for analog cameras?

Yes, with a pair of video baluns, one at each end, which convert the coax signal so it can travel over the twisted pairs in a network cable. Some baluns also send power over spare pairs. Use solid copper network cable and check that the baluns match your camera's video format.

Can I run CCTV cable in the same conduit as mains wiring?

It is best not to. Mains wiring next to coax is a common cause of interference lines, and local wiring rules may not allow it. Keep the runs separate and check local rules with a qualified electrician if you have no other route.

Do I need a separate power supply for each camera?

Not necessarily. A single power box with one output per camera is tidy and common, ideally with a fuse per output so one fault does not take down every camera. One plug-in adaptor per camera also works. Either way, make sure the supply can handle all cameras with their infrared lights on at the same time.

How do I hide CCTV cable on the outside of a house?

Run it along gutters, fascias or corners where it is less visible, inside outdoor-rated conduit or trunking painted to match the wall. Enter the building as close to the camera as you can, with a drip loop before the entry hole. Avoid leaving cable within easy reach, where someone could cut it.

Can I extend a coax cable that is too short?

Yes, with a BNC barrel joiner for the coax and a DC joiner for the power pair. Every joint is a possible failure point, so keep joints indoors or inside a weatherproof box, and avoid stacking several joiners on one run. If you need a lot of extra length, a new continuous run is usually more reliable.