Abstract :
Beginning with the first 12-metre transmitters adapted from ionospheric research equipment, the history of the extension towards shorter and shorter wavelengths is traced over the decade 1935¿45, concluding with an indication of the elements of a 3-cm r.f. unit. The major Service equipments are described with special reference to the technical advances they exhibited, particularly on the modulation side. The circuit fundamentals of the duplexing devices (T.R. switches), which may normally be regarded as part of the transmitter, are also given.
