| 摘要 |
PURPOSE:To increase the erasing frequency as the travelling speed of a magnetic medium increases and to enhance the reproducing performance for a magnetic recording and reproducing device of AC erasing system, by setting the erasing frequency at >=300kHz with the travelling speed of the magnetic speed set at 19cm/s. CONSTITUTION:The recording is carried out to a new magnetic tape 1 and when the tape is reproduced while the travelling speed of the tape 1 is set constant and an AC oscillator 5 for erasing head is stopped. The output level of an output reproducer 8 under such conditions is compared with the output level of the reproducer 8 which is obtained when the recording is carried out to the tape 1 in a state under which the oscillator 5 is actuated. The difference (degree of deterioration) varies along with the frequency of the oscillator 5. For instance, the speed of the tape 1 is set at 38cm/s and the tape 1 uses the magnetic powder of gamma hematite with the recording frequency set at 25kHz. In such case, the frequency of the oscillator 5 is varied as shown in the diagram. Thus an erasing frequency is selected to be suited to the travelling speed of the magnetic tape. |
