Both frequency and phase modulation of the r-f carrier or audio sub-carrier have received a considerable amount of thought and study. It may be that here lies the secret of successfull long distance transmission of radio facsimile.
The following citations are typical of the published or issued patent art covering this method of transmission.
Alexanderson (U. S. Patent 1,830,586, E. F. W. Alexanderson).
Runge & Schroter (U. S. Patent 1,914,898, W. Runge and F.Schroter).).
Schroter (U. S. Patent 1,937,131, F. Schroter).
Newa (Journal I.E.E., Japan, Vol. 54, No. 5, p. 433, May, 1934, Y. Newa).
Osawa (Rep. of Rad. Res. in Japan, Vol. 4, No. 3, pp. 48-49, October, 1934, Z. Osawa).
Hammond, Jr. (U. S. Patent 1,977,438, J. H. Hammond, Jr.).
Wright & Smith (U. S. Patent 1,964,375, G. M. Wright and S. B. Smith).
Aamodt (U. S. Patent 2,094,052, T. Aamodt).
R. K. Potter (U. S. Patent 1,777,016, R. K. Potter).
- (C) Marius Rensen