| 摘要 |
PURPOSE:To obtain an excellent reproduced sound and also to decrease disturbance to the reproduced picture quality by bringing two sound carrier frequencies in the helical scanning type magnetic recording and reproduction to a specific number of multiple of the frequency of a horizontal synchronizing signal. CONSTITUTION:The FM sound carrier is used twice and both frequencies are brought into an integral number of multiple of the frequency fH of the horizontal synchronizing signal. That is, the 1st sound signal 1 is inputted to an FM modulation circuit 38, where the signal is frequency-modulated and the result is fed to a mixing circuit 39. An output of the circuit 38 is inputted to a frequency division circuit 40, and after n1 frequency division, the result is fed to a phase comparator circuit 41. Then the carrier frequency f1 of the FM modulation circuit 38 is locked to the relation of f1=n1.fH/2 through the constitution of PLL. The 2nd sound signal 1' is inputted similarly to an FM modulation circuit 43 so as to lock the carrier frequency of the FM modulation circuit 43 in the relation of f2=n2.fH/2. Thus, the f1, f2 are fixed stably so as to bring the beat frequency to a frequency having a minimum energy of the spectrum of a low frequency chroma signal. |
