1、CCIR RECMN*702-1 72 = 4855212 0519230 860 = Rec. 702-1 1 RECOMMENDATION 702- 1 SYNCHRONIZATION AND MULTIPLE FREQUENCY USE PER PROGRAMME IN HF BROADCASTING (Question 62/10) (1990-1992) The CCIR, considering a) that the overloading of the HF bands is well known; b) that Article 17, No. 1751, of the Ra
2、dio Regulations, states: “., their number (of frequencies) should be the minimum necessary to provide satisfactory reception of the particular programme in each of the areas for which it is intended ,”; C) that the WARC “2-87 recognized that the synchronization of transmitters is an accepted techniq
3、ue for improving the efficient use of the spectrum, recommends that, wherever possible, only one frequency should be used to radiate a particular progrme to a given 1. reception area; 2. that over certain paths, e.g. very long paths, those passing through the auroral zone, or paths over which the pr
4、opagation conditions are changing rapidly, it may be found necessary to use more than one frequency per programme; 3. that in certain special circumstances, namely: - where the depth of the required service area extending outwards from the transmitter is too great for it to be served by a single fre
5、quency; when highly directional antennas are used to maintain satisfactory signal-to-noise ratios, thereby limiting the geographical area covered by such antennas; where the required service area subtends an azimuth angle greater than can be served by a single directional antenna, - - more than one
6、frequency per progrCamme or synchronization could be used as appropriate; 4. that synchronized transmitters: - at the same site, driven by a common oscillator and modulated by the same progrme in the correct phase; at separate sites, driven by separate oscillators, the frequencies of which are preci
7、sely controlled (a carrier frequency difference of O. 1 Hz or less) and modulated by the same programme, - should be considered as not introducing any appreciable deterioration in reception. This conclusion is valid: - for non-overlapping coverage areas; - for overlapping coverage areas, provided th
8、at due consideration is given to: - - - the shape and size of the reception area; the availability of suitable transmitting antennas; the propagation conditions over the respective transmission paths. The use of synchronized transmitters with overlapping coverage areas can lead to an improvement in the efficiency of spectrum utilization.
