Continuous Waves in Long-Distance Radiotelegraphy

Ability to predetermine the probable normal daylight sending radius of high-powered radiotelegraphic stati ons is of prime importance in their design. The theoretical transmission equations for both continuous and damped waves are discussed and the empirical formulas for the latter are given. Experiments with continuous waves over a period of six months between San Francisco and Honolulu, a distance of 2100 nautical miles (3880 km.), are described, and an empirical formula for the calculation of probable sending radius with such waves is proposed. This is checked by experiments between Tuckerton, N. J., and Honolulu, 4330 nautical miles (8000 km.). Curves giving the energy received at Honolulu from San Francisco under both day and night conditions are shown, and the effects of changes in wave length upon transmission efficiency are discussed. Evidence strengthening theories of the reflection, refraction and interference of Hertzian waves in long-distance transmissions, and experimental data showing interference bands not over 18 miles in width, are given. The great value of easy and rapid changes in wave length, especially at night, is apparent from the curves. Final conclusions drawn from a comparison of the empirical transmission formulas for continuous and for damped waves are that the transmission efficiency of continuous waves is somewhat higher than that of damped waves on wave lengths of approximately 3000 m. or above, and that this advantage increases with the wave length.