Progress in Radio Communication

Abstract

A paper by Col. A. S. Angwin giving a review of the progress of radio communication for the year 1934 (J. Inst. Elec. Eng., Feb. 1935) is of general interest. The great technical progress made in broadcasting during the last two years is reflected in its rapid development. At the beginning of 1932, the number of licensed listeners in Europe was nearly 14 millions, and two years later it was nearly 20 millions. In 1929 the total power used in broadcasting was 420 kilowatts, whilst five years later it was more than ten times greater. Now that an average high-power station consumes 2 million electric units a year, it is important to use only transmitters of high efficiency. The extended use of short-wave telegraph working in ships has enabled the British P.O. stations to communicate regularly with whaling boats in the antarctic and in eastern waters. Directive aerials have been erected at these stations covering all the main shipping routes of the world, and this has greatly improved the services. Additional radio-telephone services from Great Britain to South Africa, Egypt and India have been opened up, while services to Japan, Shanghai, Kenya and Iceland are projected. By. extension to circuits already existing, radio communication is now possible with nearly all the South American States. The outstanding feature in radio research has been the intensive study with the help of the cathode ray oscillograph of the propagation of waves in the ionosphere. The methods now in use indicate that the reflected signal resulting from a single pulse incident on the ionosphere consists frequently of a doublet the components of which are separated by a small time-interval. The reflected components are apparently electrically polarised waves of opposite rotational sense.