INTERNATIONAL TELECOMMUNICATION UNION RADIOCOMMUNICATION BUREAU (Direct Fax No. +41 22 730 57 85) Administrative Circular CAR/5 12 April 1994 TO THE ADMINISTRATIONS OF MEMBERS OF THE ITU Proposed approval of 9 draft new and revised Recommendations adopted by Radiocommunication Study Group 6 at its meeting on 10 to 11 March 1994 At the meeting of Radiocommunication Study Group 6 (Radio-wave propagation in ionized media), held on 10 to 11 March 1994, the Study Group unanimously adopted the texts of 9 draft new and revised Recommendations, and agreed to apply the procedure of Resolution ITU-R 1 (see § 10) for approval of Recommendations between Radiocommunication Assemblies. The titles of these Recommendations are given in Annex. Having regard to the provisions of § 10.4.1 of Resolution ITU- R 1, I should be grateful if you would inform me by 12 July 1994, whether your Administration approves or does not approve these draft Recommendations. A Member who indicates that a draft new or revised Recommendation should not be approved is requested to advise the reason and indicate possible changes in order to facilitate further consideration by the Study Group during the study period. After the above-mentioned deadline, the Director of the Radiocommunication Bureau will notify the results of this consultation by administrative circular and make arrangements for the Recommendations to be published in accordance with Resolution ITU-R 1. Richard C. KIRBY Director Annex: List of documents with titles and summaries Documents attached: Documents 6/BL/12 to 6/BL/20 Distribution: Administrations of Members of the ITU ***** ANNEX List of titles of the 9 draft new and revised Recommendations adopted by Radiocommunication Study Group 6 (Geneva, 10 to 11 March 1994) Draft new Recommendations Draft new Recommendation ITU-R PI.[Doc. 6/38] Doc. 6/BL/12 METHOD FOR PREDICTING SKY-WAVE FIELD STRENGTHS IN THE FREQUENCY RANGE 1 605 TO 1 705 kHz The Recommendation fulfils the need for a sky-wave propagation prediction method for use by the broadcasting service in the band 1 605 - 1 705 kHz. Recognizing that portions of the band are used by other services in different Regions, the method may also be used to predict potential interference between the services concerned. Draft new Recommendation ITU-R PI.[Doc. 6/53] Doc. 6/BL/13 PROPAGATION FACTORS AFFECTING FREQUENCY SHARING IN HF TERRESTRIAL SYSTEMS Material is presented responsive to Question ITU-R 219/3 covering those propagation factors that should be taken into account when designing, planning and operating radiocommunication services or systems in the HF band. The importance is stressed of propagation loss in determining whether required compatibility is achieved and advantages of dynamic frequency sharing are outlined. Draft revised Recommendations Draft revision of Recommendation ITU-R PI.684 Doc. 6/BL/14 PREDICTION OF FIELD STRENGTH AT FREQUENCIES BELOW ABOUT 500 kHz The revision represents a propagation prediction procedure for sky-wave field strength at frequencies below about 500 kHz. Two methods - the wave hop method and the waveguide mode method - are described, together with guidance as to their conditions of application. Draft revision of Recommendation ITU-R PI.372-5 Doc. 6/BL/15 RADIO NOISE Radio noise is an essential factor in system design over the whole radio spectrum. This Recommendation consolidates into a single text current information from Study Groups 1, 5, 6 and 8 relating to radio noise of natural and artificial origin. Draft revision of Recommendation ITU-R PI.845 Doc. 6/BL/16 HF FIELD-STRENGTH MEASUREMENT The Recommendation promotes development of a consistent data base of high frequency measurements, required for improvement in prediction methods. It specifies a standard procedure for carrying out a measurement campaign. The revision refines details on the installation of a receiving antenna, in Appendix 1 to Annex 2 of the Recommendation. Draft revision of Recommendation ITU-R PI.531-2 Doc. 6/BL/17 IONOSPHERIC EFFECTS INFLUENCING RADIO SYSTEMS INVOLVING SPACECRAFT The Recommendation describes the ionospheric effects on radio signals to be taken into account in the design and planning of Earth-space systems. Both large-scale changes due to the variation of electron density, as well as smaller scale irregularities affect the signal. The effects include scintillation, absorption, variation in direction of arrival, propagation delay, dispersion, frequency change and polarization rotation. The revision incorporates new material relating to scintillation at high latitudes. Draft revision of Recommendation ITU-R PI.844 Doc. 6/BL/18 IONOSPHERIC FACTORS AFFECTING FREQUENCY SHARING IN THE VHF AND UHF BANDS (30 MHz - 3 GHz) The Recommendation treats ionospheric propagation over long distances at VHF and above which can take place with relatively small losses. Propagation mechanisms, such as normal F-region, trans-equatorial, sporadic-E, meteor-trail ionization and auroral ionization may be significant in causing interference at these frequencies, particularly for systems requiring high reliability. The revised version draws a distinction between effects on terrestrial and Earth-space paths. Draft revision of Recommendation ITU-R PI.842 Doc. 6/BL/19 COMPUTATION OF RELIABILITY AND COMPATIBILITY OF HF RADIO SYSTEMS The revised Recommendation now includes a procedure for evaluating reliability in the presence of multiple interference and a method of estimating compatibility, which term is newly defined. The cases are included where the multiple interferers have differing frequency offsets from the wanted signal and where these apply over paths at different latitudes with varying fading statistics. Draft revision of Recommendation ITU-R PI.533-3 Doc. 6/BL/20 HF PROPAGATION PREDICTION METHOD The recommended ITU-R method of estimating HF sky-wave signal strengths and signal/noise ratios is enhanced by including the antenna gain package of Recommendation ITU-R BS.705 and the latest techniques of reliability evaluation from Recommendation ITU-R PI.842. A number of relatively minor improvements are included in the determination of various intermediate parameters such as solar-zenith angle and electron gyrofrequency. Standardisation factors against the measurement data base have been re-evaluated and incorporated. ___________________________