Radio-telegraphic transmitters

This paper deals only with the generation of high-frequency currents and the means of controlling them. A few particular features of interest are described rather than general descriptions. The paper is divided into five sections :¿ (1) Spark transmitters.¿The Timed Spark system as employed at Carnarvon and Stavanger is described. (2) The Poulsen arc.¿A short description of the underlying theory is given. The practical construction of an arc set is described, together with the means of controlling it. (3) The high-frequency alternator.¿The lay-out of the Lyons station is described and the precautions taken to obtain constant speed are indicated. (4) Valve transmitters.¿The valve is still in the first stages of development as a means of generating highfrequency currents for large powers, but the circuits employed are almost fully developed. Circuits are described and figures given for the larger types of valve and for transmitting circuits. (5) Conclusion and future developments.