INTERNATIONAL TELECOMMUNICATION UNION RADIOCOMMUNICATION BUREAU (Direct Fax No. +41 22 730 57 85) Administrative Circular 11 April 1994 CAR/4 TO THE ADMINISTRATIONS OF MEMBERS OF THE ITU Proposed approval of 19 draft new and revised Recommendations adopted by Radiocommunication Study Group 5 at its meeting on 7 to 9 March 1994 At the meeting of Radiocommunication Study Group 5 (Radio-wave propagation in non-ionized media), held on 7 to 9 March 1994, the Study Group unanimously adopted the texts of 19 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 11 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 5/BL/29 to 5/BL/47 Distribution: Administrations of Members of the ITU ANNEX List of titles of the 19 draft new and revised Recommendations adopted by Radiocommunication Study Group 5 (Geneva, 7 to 9 March 1994) Draft new Recommendations Draft new Recommendation ITU-R PN.[Doc. 5/48] Doc. 5/BL/29 PROBABILITY DISTRIBUTIONS RELEVANT TO RADIO-WAVE PROPAGATION MODELLING The draft new Recommendation contains general information on the most important probability distributions used in radiowave propagation modelling. The text provides a common background to the statistical methods for propagation prediction used in the Recommendations of the ITU-R Study Groups. Draft new Recommendation ITU-R PN.[Doc. 5/57] Doc. 5/BL/30 DIGITAL TOPOGRAPHIC DATABASES FOR PROPAGATION STUDIES The draft new Recommendation gives advice on the type of information which should be contained within topographic databases and, in particular, the resolution of terrain data suitable for propagation predictions. Additional data are also suggested for the description of ground cover. Draft revised Recommendations Draft revision of Recommendation ITU-R PN.369-5 Doc. 5/BL/31 REFERENCE ATMOSPHERE FOR REFRACTION The revision contains a minor modification to express the atmospheric profile in terms of scale height. Draft revision of Recommendation ITU-R PN.453-3 Doc. 5/BL/32 THE RADIO REFRACTIVE INDEX: ITS FORMULA AND REFRACTIVITY DATA The revised text is brought into line with the revision to Recommendation ITU-R PN.369 as regards the atmospheric profile and clarification is added regarding the derivation of the maps of surface refractivity provided in the Recommendation. Draft revision of Recommendation ITU-R PN.834 Doc. 5/BL/33 EFFECTS OF TROPOSPHERIC REFRACTION ON RADIO-WAVE PROPAGATION Two new sections have been added to the Recommendation. The first, on effective radio path length, gives expressions for excess path length on a satellite path as a function of the prevailing refractivity conditions. The second new section concerns propagation in ducting layers and provides useful information on the trapping of radiowaves into ducts as a function of elevation angle and wave frequency. Draft revision of Recommendation ITU-R PN.835 Doc. 5/BL/34 REFERENCE STANDARD ATMOSPHERE FOR GASEOUS ATTENUATION The revision contains two small modifications in order to express the standard exponential profiles in terms of scale height. Draft revision of Recommendation ITU-R PN.837 Doc. 5/BL/35 CHARACTERISTICS OF PRECIPITATION FOR PROPAGATION MODELLING The revision draws attention to the availability of a digitized version of the rainfall climatic zone maps and to the associated software that gives the corresponding rainfall rate distribution for any specified location. Draft revision of Recommendation ITU-R PN.840 Doc. 5/BL/36 ATTENUATION DUE TO CLOUDS AND FOG The Recommendation has been extended to include a formula for the refractive index of water to allow numerical evaluation of attenuation in clouds and fog as given by the Figure contained in the existing text. Draft revision of Recommendation ITU-R PN.525-1 Doc. 5/BL/37 CALCULATION OF FREE-SPACE ATTENUATION The revision brings the Recommendation up-to-date by the removal of nomograms, the rationalization of symbols and the inclusion of some formulae for the conversion between field strength, transmission loss and power in practical situations concerning free-space propagation. Draft revision of Recommendation ITU-R PN.341-2 Doc. 5/BL/38 THE CONCEPT OF TRANSMISSION LOSS FOR RADIO LINKS Modification has been made to the section concerning the influence of the environment on the operation of a pair antennas forming an elementary circuit. Formulae are given for power flux density, effective capture area of the receiving antenna and the transmission loss as functions of antenna heights, antenna separation and wavelength. Draft revision of Recommendation ITU-R PN.526-2 Doc. 5/BL/39 PROPAGATION BY DIFFRACTION A new section has been included treating a finite width screen, relevant to the suppression of interference at a receiving site such as a small Earth station. The model provides estimates for the average and minimum diffraction loss as a function of location. In addition, significant revision has been made to the section giving a general treatment for diffraction over one or more obstacles using the cascaded cylinder model. Bearing in mind that the method is used elsewhere in Recommendations dealing with the evaluation of interference signals, attention has been paid to providing clear guidance on the calculation of the relevant cylinder parameters and to the computation of sub-path diffraction losses. Draft revision of Recommendation ITU-R PN.833 Doc. 5/BL/40 ATTENUATION IN VEGETATION The revised Recommendation now draws a distinction between attenuation due to vegetation through long stretches of woodland, such as for terrestrial paths, and for short stretches, such as for land-mobile satellite paths. The Figure giving specific attenuation in vegetation has been updated. Draft revision of Recommendation ITU-R PN.370-5 Doc. 5/BL/41 VHF AND UHF PROPAGATION CURVES FOR THE FREQUENCY RANGE FROM 30 MHz TO 1 000 MHz Broadcasting services The revised version provides new advice on terrain clearance angle corrections, receiving antenna height gain corrections and the treatment of effective transmitting antenna heights below 37.5 and above 1200 m. The Figure providing the field strength variability due to receiver location has been modified to include wide-band systems. The text of the Recommendation now contains the well-known procedure for dealing with mixed land/sea paths. Draft revision of Recommendation ITU-R PN.681 Doc. 5/BL/42 PROPAGATION DATA REQUIRED FOR THE DESIGN OF EARTH-SPACE LAND MOBILE TELECOMMUNICATION SYSTEMS The Recommendation has undergone major revision. It contains models on slant-path fade depth and fade duration statistics and treats multipath situations for mountainous terrain and for roadside environments with trees. Draft revision of Recommendation ITU-R PN.310-8 Doc. 5/BL/43 DEFINITIONS OF TERMS RELATING TO PROPAGATION IN NON-IONIZED MEDIA The new text contains a revised definition for obstacle gain and sees the introduction of a definition for site shielding. Draft revision of Recommendation ITU-R PN.311-6 Doc. 5/BL/44 ACQUISITION, PRESENTATION AND ANALYSIS OF DATA IN STUDIES OF TROPOSPHERIC PROPAGATION Many of the parameter descriptions have been clarified and the formats rationalized. A completely revised table for worst month multipath channel characteristics and outage times on line-of-sight paths has been introduced. Draft revision of Recommendation ITU-R PN.530-4 Doc. 5/BL/45 PROPAGATION DATA AND PREDICTION METHODS REQUIRED FOR THE DESIGN OF TERRESTRIAL LINE-OF-SIGHT SYSTEMS The revision proposes improvement of the prediction of multipath fading and enhancement for the climatic model using refractivity gradient statistics from Recommendation ITU-R PN.453; also proposed, is a new prediction method for conversion from worst month to annual statistics. Draft revision of Recommendation ITU-R PN.618-2 Doc. 5/BL/46 PROPAGATION DATA AND PREDICTION METHODS REQUIRED FOR THE DESIGN OF EARTH-SPACE TELECOMMUNICATIONS SYSTEMS The revision contains a small, but significant, modification to the method of calculation for XPD. Draft revision of Recommendation ITU-R PN.452-5 Doc. 5/BL/47 PREDICTION PROCEDURE FOR THE EVALUATION OF MICROWAVE INTERFERENCE BETWEEN STATIONS OF THE SURFACE OF THE EARTH AT FREQUENCIES ABOVE ABOUT 0.7 GHz The modifications essentially concern the method for calculating diffraction signals, bringing the text into line with the full description of the diffraction model contained in Recommendation ITU-R PN.526. Some further attention has also been paid to procedural layout with some clarification of parameter descriptions.