By Michael F. Jeffers, Jerrold Division General Instrument Corporation
Phase Lock and Sync Lock are tools that can be used to reduce distortion and favorably change the subjective appearance of the interference seen in the background of a television channel. The use of these tools allows systems carrying fifty or more channels to serve the same geographical area formerly limited to thirty-five channel distribution. Effects of Cross Modulation and Composite Triple Beat will be discussed, and it will be proven that the Triple Beat mechanism is the predominant source of distortion. The phase-lock technique will be explained analytically showing the mechanism which causes the subjective transition of distortion from low frequency beats to sliding video frames. The report will also discuss further additional improvements in system tolerance using sync-lock and sync suppression.