| 摘要 |
PURPOSE:To simply measure a carrier to noise (C/N) rate and a composite triple beat rate by sampling a composite video signal during the non-modulation period of a TV signal, finding out the average value of synchronizing signals and calculating the C/N rate in the carrier frequency of a specific channel from the peak value and average value of the synchronizing signals. CONSTITUTION:A spectrum analyzer 10 samples a composite video signal during the non-modulation period of a TV signal and measures the effective value of a peak in the synchronizing signals of a carrier and the frequency of the carrier. In this case, the averaging mode of samples is selected, the number of lines of a TV signal is adjusted and a vertical blanking interval part is set up on the center of a display screen. Two impulses out of plural ones obtained from vertical synchronizing pulses are specified and an averaged sample or the like is obtained from the center part. After stopping the entering operation, the center amplitude value of the impulses is set up as noise amplitude. Then a C/N value is calculated from the absolute value of the peak of the synchronizing signals and the measured noise value. |
