Abstract
A digital ground broadcasting will be started in the year 2000. The digital broadcasting have the advantage of distinct pictures in comparison with the analog systems on low carrier to noise ratio. The TV broadcasting signals level has varied in sine wave shape, and repeated the fluctuation of the signal level for ten and several seconds by passing airplane. The quasiperiodic level fluctuation exceeding 2dB was sometimes more than 4dB. This phenomenon was derived by the modeled and given calculations. It has understood that the receiving antenna directivity influences the characteristics.
