The Reliability of Short-Wave Radio Telephone Circuits

W ITHIN a comparatively few years short-wave radio telephone circuits have become an important part of the international communication network. These years have represented a wide variety of experience ranging between the quiet and the disturbed extremes of an eleven-year sunspot cycle. An attempt is made here to review some of this transmission experience in a quantitative way and show certain relations that may be useful in the engineering of short-wave circuits. During a magnetically disturbed year, such as 1930, a low-power short-wave transmitter with a simple antenna arrangement would have provided very uncertain means for communication across the North Atlantic. The percentage of time that such equipment could transmit what according to lenient standards in terms of noise-to-signal ratio are useful telephone signals, would have been very low. If the power of the transmitter were increased or a directive antenna employed to reduce the noise-to-signal ratio the percentage useful time would, as based upon the same standards, be increased or conversely the percentage lost time decreased. Any improvement which will decrease *To be presented at joint meeting of U.R.S.I, and I.R.E., Washington, D. C., May 1, 1936. 181