WIRELESS

Nelson Evening Mail, Volume LXVI, 16 April 1932, Page 3

WIRELESS

LONG WAVE BROADCASTING POSSIBILITY OF 1500 OR 2004 METRE SUBJECT ENGAGING RADIO ENGINEERS 'I lie investigations of the “Coverage ’ Commission set up by the Broadcasting Board, will doubtless include a survey of Hie possibilities of 1500 or 2000 metre broadcasting as a solution to New Zealand's national coverage problem. The failure of 2YA lo give the service expected of it, in certain areas, is well known. There, lias recently been a revival of technical interest in broadcasting on wavelengths around 1500 moires. Broadly speaking the aerial energy ol a transmitting station produces pressure waves which travel to the reception point, by two different routes —one following approximately tlie contour of the land and known as flic ground wave while (he oilier is launched into space at an angle above tlie horizontal plane and only reappears on tho earth s surface aua'in due (o reflection and refraction from the Heaviside layer. The ground wave provides the useliil energy in localities near the transmitter while the space wave becomes of the major importance in very long distance reception. At, certain distances and under certain conditions ground wave and space wave interfere with one another badly and caused severe fading and distortion

Tlie space wave coming by the devious route is more subject to disturbances and distortion, it is only because of its usw fulness at comparatively great distances that it is tolerated. It is impossible to secure consistent first class reception when reiving on the space wave. The area covered by the groumlwavc of a station is more a function of wa-vc-iengtiL than ot power, and there is more or less definite mileage limit (for a given wavelength) which increases of power will not appreciably extend. it so happens that the possible effective groundwave radius is considerably greater for a 2000 metre wave than for, sav, a 400 metre wave, so that by adopting a long wavelength it is possible to bring a. greater number of listeners within tlie zone of assured reception free from tlie distractions of fading and dis tortion. hi general it may be said that 200-000 metre wavelengths have greater claims for reception at extra distances particularly at night- time, while 1500 metre waves give more consistent and •■cliahlo reception at moderate distances--reception under daylight conditions is also considerably improved. It is in tiie.se respects that longwave broadcasting is now engaging (lie attention of radio engineers in various parts of Hie, world.