| 摘要 |
PURPOSE:To quantitatively evaluate the modulation noise by providing a detecting means which takes out a modulation noise component superposed on a reproduced FM signal, a filter means which takes out a desired frequency component, and a frequency analyzing means. CONSTITUTION:With respect to a signal to be recorded on a video tape 9, a sine wave having a single frequency in the video signal frequency range is inputted from an external signal generator 6 and a horizontal synchronizing signal and its high frequency component are eliminated. The reproduced FM signal is led to an envelope detecting circuit 3, and only the modulation noise component superposed on a carrier signal is taken out and is led to a frequency analyzer 5 through a filter circuit 4, and only the modulation noise component generated between the video tape 9 and heads 7 and 8 is taken out and is quantized. Thus, the frequency component of modulation noise and its quantity are accurately detected to evaluate the electromagnetic characteristic of a magnetic recording medium.
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