Video Baluns for CCTV: Fix Lines, Noise and No Video

12 min read · Oct 21, 2026

When video baluns for CCTV give you rolling lines, snowy noise or a "No Video" channel, the cause is usually one of three things: the two baluns do not match each other or the camera's signal type, the two wires of the video pair are swapped at one end, or power is sharing a pair with the video. Less often, it is the network cable itself or a mains cable running alongside it. Test those causes in the order below, changing one thing at a time.

This guide is for wired analog and HD-over-coax cameras that feed a DVR through network cable. If your camera is a Wi-Fi or IP camera, you do not need baluns at all, and the section near the end explains why.

How a balun system works, in one minute

A video balun is a small adapter that lets a coax-type video signal travel over one twisted pair inside a network cable. You always need two: one at the camera, one at the DVR. The camera end takes the BNC plug from the camera, and the DVR end gives you a BNC plug again for the recorder's input.

There are a few common types, and knowing which you have matters for troubleshooting:

Passive baluns. No power needed. The most common kind. They work well over moderate runs, but their usable distance is shorter for HD signals than for older standard-definition video. Check the rating printed on the packaging for your resolution.
Active (powered) baluns. Usually only at the DVR end, with a small amplifier inside. Used for longer runs or when passive baluns give a soft or noisy picture.
Power-video baluns. These carry the camera's DC power over separate pairs in the same network cable, with a power jack at each end. Handy, but they add more places for a fault.

Inside the cable, video uses one pair: two wires twisted together, one solid colour and one striped. The twisting is what cancels interference. Anything that breaks that pairing, such as using one wire from the blue pair and one from the green pair, cancels the benefit and brings the noise back.

First, read the symptom

Write down exactly what you see on the DVR before changing anything.

What you see	What it usually points to
Thin horizontal lines drifting slowly up or down	Interference: mains wiring nearby, a ground loop, or a split pair
Picture rolling or tearing, colour flickering	Signal type mismatch, or a balun not rated for HD
Snow or grain that gets worse at night	Weak signal: run too long for passive baluns, poor cable, poor termination
Ghosting or a faint double image	Impedance problem: mixed balun brands, untwisted wires at the terminals
Black and white only, no colour	Weak signal or wrong signal format on the DVR channel
"No Video" on that channel	Polarity swapped, broken wire, wrong pair, or no power to the camera

If every camera on the system shows the same fault, look at the DVR, the shared power supply and the common cable route first. If only one camera is affected, our guide to tracking down why one CCTV camera is not working has a swap routine that pairs well with the checks below.

Step 1: Prove the camera and DVR channel work without the baluns

This is the most useful test, and people skip it. Take the camera down or bring the DVR to it, and connect them with a short coax patch lead, no baluns and no network cable. Use the camera's own power adapter.

Clean picture with a short coax lead: the camera, its power and the DVR channel are fine. The fault is in the baluns or the cable run.
Same fault with a short coax lead: the baluns are not the problem. Check the DVR channel's input format and the camera's output mode. Our article on a TVI camera showing no picture on the DVR walks through that setting. If the screen is completely black even here, see how to fix a CCTV camera with no video.

Only move on when you have a clean picture on the short lead.

Step 2: Check that the baluns match each other and the camera

Mismatched baluns are behind a lot of noise and ghosting problems. Check these points on both baluns:

Same make and model at both ends. Baluns from different makers may be built to slightly different designs. A mixed pair can work, but it is the first thing to rule out.
Rated for your camera's signal type and resolution. Older baluns made for standard-definition video often struggle with HD-over-coax signals. The packaging or label should state which formats and resolutions it supports. If it says nothing about HD, assume it was not built for it.
Passive at both ends, or active receiver at the DVR end only. Do not put two active receivers on one run, and do not put an active unit at the camera end unless the instructions say so.

A quick check: connect the camera to the DVR through both baluns with a short network patch lead, a metre or two long. If the picture is clean, the baluns work as a pair and the problem is in the long run. If it is already noisy over a short lead, replace the baluns with a matched pair rated for HD.

Step 3: Check polarity and the pair you used

Most baluns have two screw terminals or push-in slots marked + and −, or a colour code. The rule is simple: the wire that goes into + at the camera end must go into + at the DVR end.

Open both baluns and note which two wires you used. Write the colours down, for example "blue on +, blue-white on −".
Compare both ends. They must be the same two wires, in the same terminals.
Confirm both wires are from one twisted pair. Two wires of different colour families, such as solid blue and white-green, form a split pair and will pick up interference.
If your baluns take the cable through an RJ45 socket instead of terminals, make sure both ends are crimped to the same wiring standard. One end on one standard and the other end on the other moves the video to a different pair.

Swapped polarity often shows as no video at all, but on some baluns it gives a faint, washed-out or negative-looking image instead. Either way, swap the two wires at one end and test again. It costs nothing and rules it out.

Step 4: Check the terminations

Bad terminations cause noise, ghosting and pictures that come and go when the cable is touched.

Keep the twist as close to the terminal as you can. Untwist only the length you need to fit the wire in the terminal.
Strip only the insulation, not the copper. Nicked copper can break later.
Tighten screw terminals firmly and give each wire a gentle pull. A wire held only by its insulation will make poor contact.
Keep the outdoor balun dry. Put it in a weatherproof junction box. Water in a balun or an RJ45 joint gives green tints, noise and slow failure over weeks.

If you have a network cable tester, test the run before reconnecting the baluns. It will show a broken wire, a short or a crossed pair in seconds.

Step 5: Separate power from video

Power is the cause people least expect. Unplug the power supply before you move or rewire any power connections.

Never put DC power on the same pair as the video. The video pair carries video only. If you are using power-video baluns, power goes on other pairs, as marked on the balun.
Try powering the camera locally for the test. Unplug the power-over-cable side and run the camera from its own adapter next to it. If the lines disappear, the problem is in the power side: a weak supply, voltage drop over a long run, or a ground loop.
Check the voltage at the camera end, not just at the supply. Thin network cable wires lose voltage over distance, especially at night when infrared lights draw extra current. A camera that is short of power often looks fine by day and then rolls, flickers or reboots after dark.
Use one power supply for the system if the lines look like slow hum bars. Cameras powered from different outlets in different parts of the building can create a ground loop. Feeding all cameras from one power box near the DVR often clears it, as long as the voltage at the far cameras is still within their rating. Some ground loops need an isolator; ask an installer if a single supply does not help.

Our guide to installing CCTV cable for a DVR system explains voltage drop on long low-voltage runs.

Step 6: Check the cable and its route

If the baluns work over a short lead but not over the real run, the cable and its route are the suspects.

Solid copper cable. Copper-clad aluminium cable looks similar and costs less, but it has higher resistance and is a common cause of weak, noisy video and poor power delivery. Scratch the copper on a cut end: silver underneath means it is not solid copper.
Distance. Every balun has a maximum distance, and it is shorter for higher resolutions. If your run is longer than the rating printed for your camera's resolution, the picture will be soft and noisy. An active receiver at the DVR end, or a shorter route, is the fix.
Mains wiring nearby. Network cable laid tight alongside mains cables, motors, fluorescent light fittings or pumps picks up interference. Lines that change when a fan, pump or light switches on are a strong clue. Re-route the cable away from them, and cross mains cables at right angles rather than running beside them.

If you need to move cable near mains wiring or work at height, switch off the power to that circuit and use a ladder safely. For anything involving the mains, use a qualified electrician.

When to get help

Call an installer or the seller when:

the camera gives a clean picture on a short coax lead, a matched pair of baluns gives a clean picture on a short patch lead, but the long run is still bad and you cannot re-route it;
you suspect a ground loop that a single power supply does not fix;
the cable runs through walls, ceilings or roof spaces you cannot safely reach;
the fault appears on several cameras at once and you have ruled out the DVR settings.

When you call, tell them what you tested and what happened at each step. "Clean on short coax, noisy with baluns on a two-metre patch lead" points straight to the baluns and saves a visit.

What about Wi-Fi and IP cameras?

Yoosee cameras are generally Wi-Fi or IP cameras that connect over Wi-Fi or a network cable straight to your router or a network switch. They send digital data, not an analog video signal, so baluns are not needed and should not be used on them. A network camera plugs directly into a network cable with an RJ45 plug at each end. If someone has put baluns between an IP camera and a switch, remove them: the camera will not connect through them.

A BNC lead on the camera means analog or HD-over-coax; an RJ45 socket or only a power lead means a network camera. Check the label or manual if unsure.

Install or resell cameras?

Balun faults are easy to prevent and slow to find after the job is closed up. A few habits help:

Buy baluns in matched pairs from one batch, and label each pair before you install it.
Use one wire colour scheme on every job, for example the blue pair for video, and write it into your job notes.
Bench test each camera with a short coax lead, then with its baluns on a short patch lead, before you pull cable.
For new projects where you have a choice, consider network cameras, which avoid baluns and the analog signal format questions altogether.

If you install or sell cameras and want to work with Yoosee, see the dealer programme.

Frequently asked questions

Do video baluns reduce picture quality?

A matched pair of good baluns over a run within their rated distance gives a picture very close to coax. Quality drops when the run is too long for the rating, the baluns are not made for HD, or the pair is split or badly terminated. If you see a difference, test the baluns on a short patch lead first.

Can I use the other pairs in the same network cable for more cameras?

Often yes: each camera needs its own pair and its own pair of baluns, and some multi-channel baluns are made for this. In practice, crosstalk between pairs can add noise on long runs, and power on a neighbouring pair can add interference. Check the balun maker's instructions for your model before sharing one cable between cameras.

Why does my balun picture only go bad at night?

At night the camera switches to infrared, which draws more power and produces a darker, grainier image that shows signal weakness more clearly. If the camera is powered over the network cable, voltage drop can make it flicker or reboot. Test with a local power adapter at the camera to separate a power problem from a signal problem.

Can I connect baluns to a Wi-Fi camera to use a longer cable?

No. Baluns carry analog video, while a Wi-Fi or IP camera sends network data. For a network camera, run network cable straight from the camera to your router or switch, or use the camera on Wi-Fi if the signal reaches. Check the camera manual for its supported connections.