By Gerald L. Bahr, Cox Cable Communications
By employing a tracking generator/receiver system, (such as an Avantek sweep system) and incorporating a local oscillator with a double-balanced mixer, you can develop a side band analyzer that greatly facilitates the requirement to measure and make adjustments to headend equipment, including video modulators.
This technique allows the channel response measurement to be made in the presence of other carriers, thus negate the requirement to turn the system headend off while making these measurements. Using this technique, the head-end and system can be measured as one integral unit, thus, with the aid of a camera, providing proof of the channel response for the total system and eliminating the need to algebraically add two or more response measurements together.