DIRECTION-FINDING.

Press, Volume LXVII, Issue 20171, 25 February 1931, Page 16

DIRECTION-FINDING.

lQ NEW WIRELESS APPARATUS. (rs.oit ou* nwji cobmspohmkt.) IONDON, January 15. Two new pieces of wireless apparatus, intended to improve and to sim- *■ plify the syßtem of direction-finding, have recently been introduced (says the aeronautical correspondent of "The Times"). One which eliminates the error, hitherto found in taking bearings by wireless at night has been adopted by the Air and is being installed at Pulham,. Norfolk. A second station in this country will be similarly equipped during this year. The' other, which automatically records the bearing of the . aircraft or ship on to'which it is. tuned,, is about • to'-be" tested by the Air .Ministry. ' The former of*these,' the "MarcdniAdcock direction-finder," is of great importance in view of the probable increase of. night flying. At present only _ the Belgian night air mail service is being worked from Croydon but" a similar German service' has been . operated, and may be resumed; and before long there will be | sight flying on some sections of'the British routes'. With the Bellini-Tosi apparatus now in use at Croydon, Pulham, and Lympne, the error in .bearings taken at night haa,amounted to lOdejj,, prls deg., There is reason, to believe also that, for similar there was an error of 10 miles in the position given by Le Bourget to RlOl just .before the disaster near Beauvais; Wireless waves at night become polarised, and change the angle at which they would normally, repcli a horizontal aerial." The new system corrects this defect by eliminating the horizontal component of the vaerial. The apparatus now being erected at ' Pulham consists of four perpendicular contained within wooden towera at the corners of a square whose diagonal, measurement in 150 ft. At the base of .each tower is a junction box from which a cable is led underground to the direction-finding, instrument in a hut tit the centre # of the 'square. Comparative tests with the, old and the new system were, made , same time ago at Chelmsford,, using the Dutch, station at'Hilversum, whose bearing is known to be 90 degrees, for : the< purpose. By the old method the ' compass needle was wandering over ■ an arc' of front 10 to .15 degrees, while tht}t controlled by the Marcorii-Adcock Byetem was generally steady, and never varied'more than a degree. , Theotherapparatusseeks to reduce the process of direction from a - highly skilled operation to something like an automatic one. At the com- » 'has -to be adjusted until, -the note 'of the 'calling instrument disappears. In, the new apparatus, the. • 'compass needle; itself swings on te the .bearing of' the distant instrument as soon as the receiver is tuned in to it. This is achieved by means of a doubleloop aerial which is rotated by an , electric motor at 600 .revolutions .a The apparatus, which is suitable only for ground stations or 1 . shipß. and could, not .be carried in an • aeroplane, has been produced by the r . International Marine Radio Company, I and will shortly be tried out at one of the Air Ministry stations.