ARINC 566A-9

Purpose: For several years following its publication in 1961,ARINC Characteristic 546 served to describe the basic VHFcommunications transceiver system of the airline industry. Towardsthe end of the sixties, however, the airlines began planning forthe implementation of a VHF SATCOM system to provide long-rangepilot-to-controller and company operational voice communications.As part of that activity, AEEC produced ARINC Characteristic566.

ARINC Characteristic 566 described two versions of an airborneVHF SATCOM terminal. In the first of these, an ARINC 546transceiver was supplemented with other units (modulationadapter/modem, preamplifier/switching unit and power amplifier) toform the terminal. In the second, a more sophisticated transceiverabsorbed the functions of the modulation adapter/modem to eliminatethis unit from the equipment complement. This transceiver becameknown as the “ARINC 566” transceiver.

25 kHz channel spacing in the aeronautical mobile communicationsenvironment was foreseen as inevitable by the airlines even beforethe preparation of ARINC Characteristic 546. As part of thatactivity, therefore, they laid careful plans to ensure that ARINC546 transceivers would not be made obsolete when the need to adoptthe closer spacing arose. Adequate transmitter frequency stabilitywas specified, as were provisions for the easy modification of IFand audio bandwidths. All these features were carried over into theARINC 566 transceiver specification when it was written somehalf-dozen years later.

It was not until April 1972, at the 7th Air NavigationConference of the International Civil Aviation Organization, thatthe international standardization of system parameters for 25 kHzchannel spacing was finalized. Reviewing this event a month laterat the Spring 1972 AEEC General Session in Montreal, the airlinesdecided that a new ARINC specification should be written to replaceCharacteristic 546. They noted that many ARINC 546 radios now inservice would reach retirement age before the 25 kHz implementationdates set by ICAO, and that no operational justification wouldexist on many aircraft for replacing them with the sophisticatedand expensive ARINC 566 SATCOM transceivers. They determined thatthe new Characteristic should describe a simple, “no-frills”, 25kHz VHF transceiver for terrestrial use only. It should, theydecided, supplement Characteristic 566 without downgrading thestature of that document as the airline industry specification forVHF SATCOM hardware.

ARINC Characteristic 566A sets out to fulfill this function.

Section 3.0 is applicable to the 25 kHz channel-spaced voice anddata modes of operation. Section 4.0 is applicable to an optional8.33 kHz channel-spaced voice mode of operation and defines onlythe characteristics specific to the 8.33 kHz channel-spaced mode ofoperation, such as the channeling, the frequency selection, theselectivity, the frequency stability, the frequency response, andthe transmitter occupied spectrum.

The characteristics in Section 3.0 are also applicable to theoptional 8.33 kHz channel-spaced voice mode of operation unlessotherwise specified in Section 4.0.

COMMENTARY: The 8.33 kHz channel-spaced mode of operation forvoice communications, if implemented concurrently with the 25 kHzchannel-spaced modes of operation, would require dual-bandwidthreceivers to ensure inter-operability of the airborne transceiverswith the current (25 kHz) and proposed European narrowband (8.33kHz) VHF voice communications systems. The narrowband mode ofoperation is limited to voice communications.

Edition:

98

Published:

01/30/1998

Number of Pages:

73

File Size:

1 file , 810 KB