Flutter in magnetic recording of data

Among the sources of error in magnetic tape recording, one of the more important is the distortion of the reproduced time scale generally described by the term "flutter." Flutter is defined as the deviation in reproduced frequency from the original recorded frequency, which results from nonuniform speed of the recording medium during recording and reproduction. The present paper provides a qualitative and quantitative discussion of flutter including: 1) Causes-eccentricities, resonances, frictional variations. 2) Effects-FM noise, AM' noise, time displacement error. 3) Measurements-methods, units and relations between them. 4) Compensation-methods and limitations. The object of the paper is to collect the essential characteristics of flutter in a way that will be of value to users of magnetic tape recording equipment.