| 摘要 |
PURPOSE:To prevent the generation of the crosstalk noise by switching alternately and every track the 1st and 2nd carrier frequencies which are out of an audible band together with the difference frequency also set outside the audible band to modulate the sound signal, modulating again the modulated sound signal with an optional frequency of a band between a chroma signal and a luminance signal to be recorded and mixing this modulated signal into the luminance and chroma signals for recording. CONSTITUTION:The sound signal is modulated by an FM modulator 61 to alternate tracks with a subcarrier of 30kHz or 60kHz. This modulated signal and a sound signal are mixed together by a mixer 64. This mixture signal is modulated again by an FM modulator 17 with a subcarrier of 1.5MHz. In a reproduction mode, the normal signals (solid lines) of a subcarrier of one side and the crosstalks (broken lines) of a subcarrier of the other side are mixed as shown in figures A and B for the signals supplied to an FM demodulator 67. Then the frequency of the subcarrier is set so that the beat frequency of said mixture is set out of a sound band. Thus it is possible to eliminate a noise component through an LPF47. |
