Abstract :
The paper briefly describes the history and the principles of m.f.s.k. signalling as applied to h.f. telegraphy. It quotes mathematical relationships for the performance of such systems, and derives equations for the occupied bandwidth. These relationships, together with the results of measurements carried out on different experimental m.f.s.k. systems, and practical limitations suggested by experience, are used to suggest an approach to the selection of optimum parameters. Systems suitable for different telegraphy and telemetry applications are derived and discussed. Practical problems of synchronization and source stability are analysed, and methods of error coding for ARQ and FEC systems are described. It is concluded that for data links in the range of 20 to 200 bits per second, the use of m.f.s.k. techniques can give an improvement in performance equivalent to about 10 dB in signal-to-noise ratio, or a reduction in error rate of the order of 10/1 in the raw data (or more than 100/1 if an error coding system is used).
