31 July 2011 C1 CIVIL AVIATION DEPARTMENT HONG KONG ...

CIVIL AVIATION DEPARTMENTHONG KONG, CHINAAirworthiness NoticeTHIS NOTICE GIVES DETAILS OF A MANDATORY ACTIONHF COMMUNICATION SYSTEMNo. 85Issue 231 July 20091 ApplicabilityThis Airworthiness Notice is applicable to Hong Kong registered aircraft issued witha Certificate of Airworthiness.2 General2.1 International Civil Aviation Organization (ICAO) has published Standards inAnnex 10 Volume III Part II paragraph 2.4.1.4 the requirements of classes ofemission and carrier suppression to Single Sideband (SSB) HF communicationsystem.2.2 The Chief Executive of Hong Kong Special Administrative Region, inexercise of the powers conferred on him by Section 2A of the Civil AviationOrdinance, as amended which gives effect to Chicago Convention, adopts theStandards in accordance with the Convention.3 Introduction3.1 The International Telecommunication Union (ITU) uses an internationallyagreed system for classifying radio frequency signals. Each type of radioemission is classified according to its bandwidth, method of modulation,nature of the modulating signal, and type of information transmitted on thecarrier signal. It is based on characteristics of the signal, not on the transmitterused.3.2 The class of emission is a set of characteristics classified and symbolisedaccording to their basic characteristics. The basic characteristics are:• First symbol – type of modulation of the main carrier;• Second symbol – nature of signal(s) modulating the main carrier;• Third symbol – type of information to be transmitted.AN-85 P.131 July 2009