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A balun is a device that connects a balanced line to
an unbalanced line. It allows a signal of one impedance value to be transmitted
over a cable that uses a different impedance. Impedance is simply a measure of
opposition to alternating current. A video balun
allows a user to send video signals over a cable not meant for video. A common
situation involving video baluns is for them to be used with Cat5 cable. Coax
cable, which transmits video, has an impedance of 75 ohm while Cat5 has a 100
ohm impedance. Baluns, therefore, convert the original impedance to the
impedance of the cable and then back. Baluns are used in pairs; you need one on
each end of the cable. Transmitting video over Cat5 without the use of video
baluns will produce a picture with ghosting as delays in the signal will occur.
The word balun is derived from the words BALance and UNbalance, as the device
takes a signal from a balanced line, converts it to a signal for use in an
unbalanced line, and vice versa. A balanced line has two conductors and is one
in which the current is equal in opposite directions while an unbalanced line
has just one conductor with current returning via a common ground. The reason
for using a balun is because Cat5 cable costs less then coax cable. Another
factor is ease of installation. The quality of video is also excellent when
using Cat5 cable. Cat5 provides for excellent balance, meaning the video signal
will not be affected by other signals. Most of the electrical noise and RF
interference which affect coaxial cables are eliminated.
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