Abstract: This application note proposes a new test method for predicting jitter contribution for imbalance (asymmetry) in serial digital-video differential cables. It exposes myths about intrapair skew as a quality indicator and about the misleading relationship between intrapair skew measurement and jitter. The article identifies the key problem as mode conversion between differential and common modes resulting from cable imbalance, as each mode has its own transmission velocity and loss characteristics. An economical cable test method of mode conversion is presented, with pass/fail criteria related directly to data jitter.

Active and Passive Video Baluns

Composite video signal normally carries a 1V peak to peak signal. Passive baluns do not alter the intensity of the signal, and merely transfers it from coaxial to Cat5 connectivity or vice versa. However, for long range applications, the signal will naturally degrade. Therefore, active baluns are useful for intensifying the signal and transmitting a stronger signal to the receiving balun. An active balun on the receiving side will receive a weakened signal and intensify it before sending it to the video surveillance appliance. The longest range active balun will boost the signal up to 5V. Active baluns come in long, medium, short, and adjustable ranges. A quality DVR machine can tolerate video signals ranging from 0.3V to 5.0V

Active and passive baluns can exist in various configurations

Purpose
Why use video baluns? Normally, coaxial cable is used to carry video between the camera and the monitor. Substituting networking cable (Cat5 or Cat6) will allow for longer runs at a lower cost. Such video can be carried over long distances, as much as 6,000 ft. Each Cat5 cable contains 8 wires. Because video is sent in pairs, one Cat5 cable can support up to 4 cameras. If fewer cameras are needed, Cat5 wires can be used to carry power, so that cameras can be powered from far away.

Phone cable can be used instead of Cat5. Phone cables are like Cat5 cables but only have six wires (three pairs of two). A normal phone number and connection uses only one pair (two wires), leaving four more wires free. These four wires can be used to carry video. Phone cables have a tremendous advantage – wiring cost efficiency. Because phone cables are already integrated into a building’s walls, all you have to do is unscrew the face plate, strip the phone cable wires, and connect it to the balun

I purchased some cheap no-name baluns through Amazon and THEN I read the discussions about some cheap baluns being only pass-through w/o the required circuitry. So what do I do? Well take one apart and find out what’s inside!