How can the effects of coherent carrier frequencies on the consistency of distortion measurement be minimized?
If the carriers in the multiple frequency generator are set for example, to within 1 kHz of the correct frequency, all the composite beats will fall within a 6 kHz band. This stresses the measurement because the high crest factor of the distortion. One way to minimize is to randomly offset the signal source frequencies by up to 5 kHz. The Matrix ASX-16B and later models have the capability to remotely adjust the carrier frequency trim. Matrix CATV Equipment control program has the capability to automatically randomize the carrier frequencies. The use of a square law detector eliminates the crest factor problem and extends the lower limit of the measurement. See MTN-110.
