"WALKIE-TALKIE" RADIOS

Chronicle (Levin), 27 November 1946, Page 7

"WALKIE-TALKIE" RADIOS

-Press Association

INNOVATION EXPLAINED

By Teleciravh-

WELLINGTON, Nov. 2(5. In a statement issued today the P-ost Office mentioned thiet for some time extensive use has been made of the radio in various countries ove'rseas for communicating with moving vehieles, notably for thp police and fire brigade serviees. In New Zealand there is a growing interest in the use of radio by local bodies and othcr operatives desiring to improve the methods of despatching and controlling the moveinents of their nrotor vehicle lleets. This interest no doubt arises from the wide use which was Made of radio during the wai' when on occasions necessity demanded contiuuous communication between sliips, aircraft, tanks and other annoured vehieles and betwcen individuals of the forees carrying "wallcietalkies. " Stimulation has been added also by the publicity given to the use of radio for police patrol cars. It has become generally lcnown by those iiitcrested tliat there is available just no w a iargo quantity of surplus Army radio-comiuunication equipinent which with niiuor modilications could be used for mobilo radio systems, but . the Post Ollico points out tliat this typo of equipment will not provide everything required for an effective service. Kesearch carried out in New Zealand coulirins the experience overseas tliat adcquate power at the central transmitting statiun is essential for a satisfactory service. The equipincnt of low power can give good results over sliort periods in the hands of trained personnel, but for longer periods reliable coininunicatioii of good quality which should be the basis of any permanent civil set-up is more diffieult to attain in view of the topograpliieal conditions obtaining 111 New Zealand. Licence to Operate Required. iSome persons are apparently unaware tliat radio transmitting cquipnient cannot be used unless a licence is issued by the Post Offi.ce. Others assume tliat iicences for various types of radio communication service will be issued as a liiatter of course togetlier with appro priate operating froqueiicies. Such fre quencies are ailotted in aceordance with an international agreement, and ovving to the increasing use of radio for ships, aircraft, navigational aids, etc., allocation is not a siniple matter. I11 fact considerabie difficulty is being e'xperienced in this respect. The Post Ollice recognises, howcver. tliat certain frequencies niust be re served for use by motor vehieles, and it has arranged for liinited bands to be available in the mediuin and verv high frequency ranges. The higlL frequcnc^ bund is not favoured for sliort distance coiiiinunications because even with the equ'ipnient of fairly low power "sky wave ' ' transmission occurs causing in terference to serviees iii other paris oi the world, and this niust be avoided. The use of mediuin frequencies niake.it possible to utilise substantial powei in the purent station transmitters, tlius providing for eifective coverage which is so necessary and avoiding interference. Overseas transmission from vehieles is not so effective 011 low frequencies owing lo Ihe sniull aeriuls used, and in the cifcumstances suitable frequencies in the 3 megacycle band have been ailotted for mobile units to permit of two-way communication using low power, tiius reducing tlie likeliliood of interference to overseas stations. Special Certificate for Operators. I11 most cases iicensees desiro tliat their existing staffs should operate the radio equipnient (which incidentalh must Iie "crystal conlrolled'"), and to nieet these cases the Post Office has issued a restricted radio-telcphono oper alors' cerlilicate. The operators ari required to pass an eleuientary exainination in the lincuipulatioii anil operalion of Ihe equipnient, but il is emphasised tliat ihe restricted certiiicate will be issued only when l-.j u]>puratus used is of a-typo "which eannoL by malad juslmeiit ereato interference to other serviees. While in certain applications an individual radio systeni is justiiied there would be lilllo difficulty in co ordinating Ihe roquirements of several aulhorities in oue area. For example, iire, umbulanee, power, traffic and otliei lucul body aulhorities, aud this is the jiolicy favoured by Ihe Post Office be ea use of the liinited nuniber of suitable radio f'requoucy chaunels and the coni jiaratively heavy cost of providing liigh grade and reliable radio conimunieation.