A new measurement for television transmission characteristics

The author describes an open-loop measurement system for determining TV transmission characteristics. Measurements of transmission from the studio to the final relay station can be performed. A teletext (digital-code-service) signal is inserted into a video signal on the same line. Two carriers are used: the measured signal is transmitted on the video carrier, and the audio carrier is used for sending the reference signal. The signal generator for the video transmitting section has a 1/2 divider adjustable to any type of line, such as a narrow audio frequency line. The receiver of the RF measured signal has a second multiplier to regenerate the reference signal. A phase comparator measures the transmitting line characteristics by comparing the measured signal with the reference signal. The reference signal accuracy of the method has been analyzed to certify the validity of the test results. When a 10-kHz subreference signal modulated at a modulation index of 30% is transmitted from a TV transmitting station to a receiving site, the calculated phase rotation angle is 0.75 rad