Interference is a major problem on CCTV systems that use coaxial cables (the so-called analog of HD coaxial CCTV systems). In most cases, interference and noise in the image can be eliminated by using good cables, the right power supplies, and by building a well-designed surveillance system.
In this article, we will talk about the CCTV interference issue and offer tips on how to eliminate noises/interference in a security camera.
What is CCTV noise?
In the CCTV field, the term noise is used to refer to the undesirable grainy-look image in your TV or monitor, especially during the nighttime. No matter how excellent and low-light capable your CCTV cameras are, there will inevitably be some noise when shooting video surveillance footage in the dark.
Noise is an unavoidable part of any electronic communication, whether video or audio. It’s essentially static – interference in the video signal that manifests as white and black spots in the frame and gives it a grainy appearance.
Inadequate, dim lighting makes it difficult for the camera to distinguish colors and contrast, resulting in pixels in the image becoming blended together instead of rendered properly and with detail.
Image noise also occurs when poor illumination causes the light in the image to be too close to the level of noise found naturally in the sensor, making it difficult for the sensor to sense the image.
However, in many cases, you have plenty of light in the environment and you’re still getting that ugly noise on the screen.
Apart from the light noise that can’t be avoided in CCTV systems, in many cases, the noise or interference is caused by improper installation techniques. You can make the interference/noiseless by trying the tips listed below.
What causes interference and noise in the security cameras?
In this section, we will explain in detail what causes the interference or noise in CCTV systems and offer a few tips on how to eliminate this phenomenon. There are several factors that can cause interference issues in security cameras.
- Use of poor quality cables
- Insufficient power supply
- Use of poor quality (cheap) cameras
- Grounding is done wrong
- Poor connections
- Not enough lighting
- Use of poor video baluns
- Use the DNR feature to get rid of the interference
1. Use of bad quality cables
Coaxial cables
A cheap coaxial cable doesn’t provide enough shielding from electromagnetic phenomena. This crucial system component is often neglected, with many users giving little thought to the cable they choose.
Not all cables are created equal, however, and a vast majority of image problems are caused by poor quality or improperly installed cables.
The typical cable of choice for a traditional CCTV surveillance system is RG59 Siamese cable. It is called “Siamese” because it is actually composed of two different cables attached to each other: a coaxial RG59 cable used to carry the video signal, and a two-wire cable (usually 18/2) used to carry the power.
For a CCTV cable, a coverage of 95% or better is recommended for proper operation. Click here for more information on coaxial cables.
UTP cables
If you’re using UTP cables (Ethernet/network cables) for your CCTV system, make sure you’re using cables manufactured by a well-known company and not some cheap Chinese manufacturer. You may save something now, but in the long run, you’ll end up spending more.
Some CAT5 cables are not pure copper but CCA or copper-coated aluminum. Don’t rely on the label or what the retailer says, actually check the cable yourself. CAT5, CAT5e, CAT6, and CAT6e can all be CCA rather than pure copper. CCA tends to break easily when bent and you can scrape the copper off to reveal silver colored metal in the center.
The maximum distance video signal can be transferred with good video baluns is approximately 300 meters (980 feet).
If you are using the cable to power a camera as well as transfer video signal then we recommend a maximum distance of about 50 meters (200 ft) to avoid voltage drop. This assumes you are using 3 pairs of wire for 12 volt supply and 1 pair for video signal transfer.
2. Insufficient power supply
In order for a security camera to operate correctly, it needs to be powered according to the manufacturing specs. Nowadays most CCTV cameras use a 12V DC (direct current) but there are also security cameras that use 24V AC power (the cable runs can be longer).
What’s the proper voltage for a camera? It’s important to get CCTV security cameras that support a 10% tolerance of voltage. This means that if the camera needs 12V DC, it can support voltage 10% above (13.2 V DC) or 10% below (10.8V DC) the standard 12V DC.
If you buy a cheap camera that doesn’t support such voltage variation, the camera may get damaged if the voltage is a little bit higher or lower.
The camera should also receive enough current (usually 1A per camera) from the power supply in order to operate properly (more amps are okay, but fewer amps will have the camera struggle).
Power-related issues often cause interference and noise in the picture, apart from damaging the system in the long run. So, if you’re experiencing interference or noise, make sure the cameras are getting enough juice from the power supply.
3. Using cheap cameras
If your go for a cheap and low-quality security camera, it won’t matter if you try to improve the infrastructure, the camera will still provide bad and grainy images. Low-cost unbranded cameras do not deliver the quality you need (or expect) for your CCTV system, especially in low-light situations.
That’s why it’s very important to research the product before you purchase it and to make sure that it fulfills the quality requirements for your CCTV project.
You should purchase security cameras from a respected manufacturer or reseller who provides technical support for their products. If you go cheap, in the long run, it will turn more expensive.
4. Grounding is done wrong
If grounding is done improperly or not done at all (which happens in many lazy projects), you may see lines moving on the screen. This type of interference is called ground loop and you can read this article for more information.
A ground loop problem may occur at several points in the system, and each occurrence of the problem must be corrected individually.
Loops can occur between a camera and monitor, from a camera to a switcher, or one of many other possibilities. The easy solution to eliminate the interference caused by ground loops is to use ground loop isolators such as this one.
5. Poor connections
Check out the power supply or coaxial cable connections to make sure that they’re done correctly and nothing’s loose. It’s not rare for the interference to be caused by poorly and unprofessionally made camera connectors or simply because the contacts are not tight.
When making and checking a connection, always double-check and never get lazy. You may save 2 minutes now but waste a whole week trying to figure out where the problem is.
6. Not enough lighting
To get a good (or acceptable) image there needs to be enough light in the environment that is under surveillance. All security cameras will struggle and show interference in a low illumination situation, however, when the camera is high end (and more expensive), this problem is minimized to the maximum.
Before purchasing a CCTV security camera, check out the night time performance on demo videos or take a look at the number of LEDs that are built-in into the camera.
Another way to improve the illumination is to install floodlights are LED illuminators in the area under surveillance. The bottom line, a cheap camera will show a lot of interference and noise in the live picture, a high-end camera will provide a way much better image.
7. Use of poor video baluns
If you are using video baluns for Cat5e or Cat6 UTP cables make sure to choose the right product. There are video baluns that work better with HD-CVI cameras or HD-TVI or AHD cameras.
You have to get the baluns that match the technology you’re using. To learn more about these technologies, read the article: Differences between HD-TVI, HD-CVI, and AHD.
Also, check the maximum distance that the baluns can be used for, read the specs, and if you have questions, double confirm it with the manufacturer. More about CCTV baluns in this article.
8. Use the Digital Noise Reduction feature
Some surveillance camera companies may include their brands in their innovative DNR technology. When it comes to CCTV, DNR is crucial for clearer images.
The image sensor on the CCD eliminates the grainy effect on the images, and consequences in a richer image. This is essential to identify any movement of objects on the screen. It helps to have DNR on surveillance cameras located in parking lots, and it comes in handy for forensic use.
Digital Noise Reduction utilizes software in the CCD to digitally remove any noise found in each image. It has an algorithm that analyses two consecutive frames and removes any grains that do not match the previous frame.
When the CCD eliminates the noise from the photo, the image is then transferred to the DVR or NVR. When it is stored on the hard disk drive (HDD), the picture size is decreased by 70% and is clearer and crisper than before.
However, the image is typically only processed in the foreground of the image. Objects in the background tend to appear grainy. Newer developments have found a solution for this. The most advanced type of digital noise reduction is called 3D-DNR, or as it is sometimes written, 3DNR.
The latest form of Digital Noise Reduction is 3D-DNR. It compares every pixel with the pixels surrounding it in addition to every frame with the next.
This process of matching is called spatial noise reduction. With 3D-DNR, thorough processing of the image is applied, including the background. This results in a clearer image than traditional DNR and less space is taken on the hard disk drive.