Effect of Uneven Slit Illumination upon Distortion in Several Types of Variable-Width Records

The effect of uneven slit illumination upon the reproduction of variable-width sound-tracks of the unilateral and bilateral types are analyzed. The ground-noise reduction for unilateral tracks is considered, as accomplished by a single-vane shutter so that the modulations are recorded symmetrically with respect to the center of the track. For bilateral tracks both electrical biasing and double-vane shutters are considered for effecting ground-noise reduction. — When the slit illumination increases linearly across the sound-track, bilateral records either with electrical or shutter ground-noise reduction are not distorted. When the illumination changes by 20 per cent across the sound-track by any uniform function that would correspond to any actual case of faulty adjustment, the harmonic distortion in no case exceeds 3 per cent for fully modulated signals. Further, the percentage of distortion decreases with the signal strength. Thus, while the reproduction of variable-width recordings is subject to distortion by uneven slit illumination, it is not excessive on equipment properly serviced.

Print ISSN

0097-5834

Published

1937-11

Content type

Original Research

DOI

10.5594/J14727