The Benefits of Using a 4 Channel Passive Video Balun

Today, many security equipment and surveillance cameras still use coaxial cables, specifically RG-59, which is a shielded cable that has an impedance of 75 ohms. By impedance, we are talking about the measure of the opposition from an electrical circuit to the passage of the current as voltage is applied through it. Shielded cables are wrapped, most commonly in aluminum, mesh wires, and plastic, preventing external noise from reaching the cable. Additionally, with shielded cables, the desired radio frequency is kept inside the cable. With an impedance of 75 ohms, ideal quality videos will only result if the objects that transmit the signal also have the same impedance of 75 ohms.

Cat5 cables, on the other hand, are more recent technological innovations, which have twisted pairs of wires. The twisting of the pairs actually allows electromagnetic interference from external sources to be canceled out. The problem with Cat5 cables though, is that it is unshielded, which means that there is no shield to prevent outside noise which comes in the form of electromagnetic radiation. This is another reason why Cat5 cables have a different name – UTP cables which stand for Unshielded Twisted Pair cable. Cat5 cables also differ from coaxial cables in one thing: it has an impedance of 100 ohms. 

The camera that has an impedance of 75 ohms and the DVR that intends to receive it at 75 ohms means that Cat5 cables are a mismatch with both the camera and the DVR, along with everything else. How do we solve this problem?

A 4 channel passive video balun is the best way to prevent loss of information that is brought about by lengthy, unshielded, or mismatched cables. With a 4 channel passive video balun, the mismatch of ohms going to and from the cable will be corrected. Additionally, external noise cancellation is also prevented as well as other video signal attributes such as white balance. A 4 channel passive video balun is specifically designed to solve these problems and fortunately for us, they come at a cheap price.

Video baluns are used in CCTV systems and some of the pieces we are familiar with include active video baluns, HDTV baluns, keystone video baluns, and rackmount video baluns. 

Notes On Using A 4-Channel Passive Video Balun

4 Port Passive Video Balun (Terminal Type), with Power, Monitor Side

First things first, what is a 4-channel passive video balun?

A 4-channel passive video balun is a specialized electrical transformer that converts differential electrical signals to unbalanced (also known as single-ended) electrical signals. A 4-channel passive video balun is used when dealing with radio frequencies. For example, when the length of the cable is too long, when it is unshielded or when it is mismatched in impedance, then there is a possibility of loss signal; this is where the 4-channel passive video balun comes in.

The majority of digital video security and surveillance cameras still use coaxial cable specifically the RG-59. The RG-59 is a shielded cable that has an impedance of 75 ohms and that has aluminum, mesh wires or even plastic sheath. These features prevent the loss of desired radio frequency in and prevent external noise from reaching the cable. Now, let’s talk about CAT5 or Ethernet cables. Ethernet cable has a twisted pair of wires that cancels out electromagnetic interference from external sources. It is also called UTP or short for Unshielded Twisted Pair cable because it contains no shield that prevents outside noise for radio frequency applications. Ethernet cables can also be used for video transmission lines for digital video security cameras, but it has an impedance of about 100 ohms. Since the camera is transmitting its video data at an impedance of 75 ohms and the DVR has to receive it at 75 ohms, then there is a clear mismatch between the Ethernet cable and everything else.

This is where a 4-channel passive video balun comes in. The video balun will correct the mismatch of ohms going to and from the cable; in addition, the balun may also correct for noise, white balance, and other video signal attributes. It also enables four different signals to be sent over one CAT5 cable that is up to 1200 feet in length. When using a 4-channel passive video balun, make sure to purchase two units. The first one converts the signal from BNC to CAT5 while the second video balun converts the CAT5 back to BNC so it can be used by the DVR.