Analysis of the recording of sine waves

Magnetic recording of the sine waves of all wavelengths is analyzed. The analysis shows that the recording process consists of two types of phenomena: 1) a virtual input scanning-the remanant tape magnetization (the recording point) appears at the front gap edge and moves over the gap towards the rear gap edge each half period. Thus, the tape is magnetically "scanned" by the input gap field in the direction opposite the tape motion. 2) A particular type of interference-as the half wavelength of tape passes over the gap, the input field will generally reverse polarity at least once. Thus, the different "scannings" on the same tape section will interfere with each other timewise. The net effect of these processes, even with the initial magnetization curve linear, is to produce a distorted tape magnetization output. The results clearly indicate that for longer wavelengths there is the greatest amount of distortion, but no amplitude attenuation or phase shift. Furthermore, in this wavelength region the recording is done over the entire gap. For smaller wavelengths, the reverse holds true; that is, there is a decreasing amount of distortion and an increasing attenuation and phase shifting. Also, the shorter the wavelength, the closer to the front gap edge is the recording point. It is also found that there is a theoretical lower limit to the wavelength that can be recorded and that at very short wavelengths the shape of the gap trailing field becomes most significant. The fact that increasing oversaturation at the shorter wavelengths decreases instead of increases the net tape magnetization is also explained.