Rec. ITU-R P.1546-1
RECOMMENDATION ITU-R P.1546-1
Method for point-to-area predictions for terrestrial services in the
frequency range 30 MHz to 3 000 MHz
The ITU Radiocommunication Assembly,
a) that there is a need to give guidance to engineers in the planning of terrestrial radiocommunication services in the VHF and UHF bands;
b) that, for stations working in the same or adjacent frequency channels, the determination of the minimum geographical distance of separation required to avoid unacceptable interference due to long-distance tropospheric propagation is a matter of great importance;
c) that the curves that appear in Annexes 2, 3 and 4 are based on the statistical analysis of experimental data,
a) that Recommendation ITU-R P.528 provides guidance on the prediction of point-to-area path loss for the aeronautical mobile service for the frequency range 125 MHz to 30 GHz and the distance range up to 1 800 km;
b) that Recommendation ITU-R P.452 provides guidance on the detailed evaluation of microwave interference between stations on the surface of the Earth at frequencies above about 0.7 GHz;
c) that Recommendation ITU-R P.617 provides guidance on the prediction of point-to-point path loss for trans-horizon radio-relay systems for the frequency range above 30 MHz and for the distance range 100 to 1 000 km;
d) that Recommendation ITU-R P.1411 provides guidance on prediction for short-range (up to 1 km) outdoor services;
e) that Recommendation ITU-R P.530 provides guidance on the prediction of point-to-point path loss for terrestrial line-of-sight systems,
1 that the procedures given in Annexes 1 to 6 be adopted for point-to-area prediction of field strength for the broadcasting, land mobile, maritime mobile and certain fixed services (e.g. those employing point-to-multipoint systems) in the frequency range 30 MHz to 3 000 MHz and for the distance range 1 km to 1 000 km.
The propagation curves in Annexes 2, 3 and 4 represent field-strength values for 1 kW effective radiated power (e.r.p.) at nominal frequencies of 100, 600 and 2 000 MHz, respectively, as a function of various parameters; some curves refer to land paths, others refer to sea paths. Interpolation or extrapolation of the values obtained for these nominal frequency values should be used to obtain field strength values for any given required frequency using the method given in Annex 5, § 6.
The curves are based on measurement data mainly relating to mean climatic conditions in temperate regions containing cold and warm seas, e.g. the North Sea and the Mediterranean Sea. The land path curves were prepared from data obtained mainly from temperate climates as encountered in Europe and North America. The sea-path curves were prepared from data obtained mainly from the Mediterranean and the North Sea regions. Extensive studies reveal that propagation conditions in certain areas of super-refractivity bounded by hot seas are substantially different.
This Recommendation is not specific to a particular polarization.
2 Maximum field strengths
The curves have upper limits on the possible value of field strength which may be obtained under any conditions. These limits are defined in Annex 5, § 2 and appear as dashed lines on the graphs reproduced in Annexes 2, 3, and 4.
Although field strengths may be read directly from the curves presented as figures in Annexes 2, 3 and 4 of this Recommendation, it is intended that computer implementations of the method will use tabulated field strengths available from the Radiocommunication Bureau. See that part of the ITU R website dealing with Radiocommunication Study Group 3.
The detailed step-by-step procedure to be used in the application of this Recommendation is given in Annex 6.
5 Designation of antennas
In this Recommendation, the term “transmitting/base antenna” is used to deal with both the concept of transmitting antenna as used in the broadcasting service and the concept of base station antenna as used in the terrestrial mobile services. Similarly, the term “receiving/mobile antenna” is used to deal with the concept of a receiving antenna as used in the broadcasting service and a mobile antenna as used in the terrestrial mobile services.
The method takes account of the effective height of the transmitting/base antenna, which is the height of the antenna above terrain height averaged between distances of 3 to 15 km in the direction of the receiving/mobile antenna. For land paths shorter than 15 km where the information is available the method also takes account of the height of the transmitting/base antenna above the height of representative clutter (i.e. ground cover) at the location of the transmitting/base station. The transmitting/base antenna height, h1, to be used for calculations is obtained using the method given in Annex 5, § 3.
The field strength versus distance curves in Annexes 2, 3 and 4, and the associated tabulations, are given for values of h1 of 10, 20, 37.5, 75, 150, 300, 600 and 1 200 m. For any values of h1 in the range 10 m to 3 000 m an interpolation or extrapolation from the appropriate two curves should be used, as described in Annex 5, § 4.1. For h1 below 10 m, the extrapolation to be applied is given in Annex 5, § 4.2. It is possible for the value of h1 to be negative, in which case the method given in Annex 5, § 4.3 should be used.