1、CCIR VOLUME*IV-1 90 W 4855232 O509866 2 10 Rec. 354-2 RECOMMENDATION 354-2 VIDEO BANDWIDTH AND PERMISSIBLE NOISE LEVEL IN THE HYPOTHETICAL REFERENCE CIRCUIT FOR THE FIXED-SATELLITE SERVICE * (Question 2/4) (1963-1970-1974) The CCIR, CONSIDERING (u) that the hypothetical reference circuit is intended
2、 as a guide to designers and constructors of actual systems; (6) that the costs of establishing and maintaining systems in the fixed-satellite service are critically dependent on the video bandwidth and the overall signal-to-noise ratio to be provided and these should, therefore, not be greater than
3、 is strictly necessary for acceptable transmission; (c) that it is desirable for the noise level in satellite transmission not to exceed the permissible level for international terrestrial transmissions (see Recommendation 567);. (d) that it is desirable for international television programmes via s
4、pace stations in the fixed-satellite service to be transmitted according to the television standards and system of origin, so as to ensure the best quality of service in conformity with Opinion 38, UNANIMOUSLY RECOMMENDS 1. that, in the hypothetical reference circuit for systems in the fixed-satelli
5、te service, as defined in Recommen- dation 352, the nominal upper limit of the video bandwidth should be compatible with the necessary bandwidth for the television system or systems to be transmitted (see Recommendation 567); 2. that the signal-to-weighted noise ratios for continuous random noise at
6、 the end of the hypothetical reference circuit, defined in Recommendation 352, should provisionally be equal to the ratios recommended for the 2500 km terrestrial reference circuit in Recommendation 567 for the appropriate television standard. Note 1 - The CMIT intends to study the definitions and c
7、haracteristics of auxiliary circuits to be associated with picture and sound programme circuits (see Study Programme 17C/CMTI). Note 2 - In the application of RECOMMENDS 2 of this Recommendation, special note should be taken of Note 2* of 0 1.2 of Recommendation 421-3 (Geneva, 1974) with regard to n
8、oise in the hypothetical reference circuit. Note 3 - The noise specified above should include the interference noise in Recommendation 483. . * These requirements are provisional. In Question iS/CMlT and Study Programme 13D/CMTT, the CMT invites Administrations to study the characteristics of a hypothetical reference circuit for the transmission of television by satellite. Note by the Secretariat: this Note has been deleted in Recommendation 567 which replaces Recommendation 421-3. _b * -_7 -
