1. The power input to the transmitting antenna shall not exceed +13dBW below 10GHz nor +10dBW above 10GHz. assignments to the IFRB for international registration, but this 2. The maximum equivalent isotropically radiated power (e.i.r.p.) action is informal and non mandatory and international registration shall not exceed 55dBW. is not always sought if interference to or from future foreign terre- strial stations is thought to be unlikely. Below 10GHz the constraint is made more stringent in the direc- However, earth stations have more powerful emissions than typi- tion of the geostationary satellite orbit. Thus, if the beam of a fixed cal terrestrial stations and more sensitive receivers; interference service transmitter is directed within 0.5° of the orbit, usually may arise at great distances and such interference may be sporadic, because it is pointed towards one of the two azimuths at which the depending, for example, on tropospheric duct propagation. A thor- line of the orbit cuts the local horizon, the maximum e.i.r.p. is ough and mandatory procedure is used to identify and eliminate 47dBW, rising in a dB linear mode to 55dBW in directions 1.5° potential cross frontier interference problems when an earth station away from the orbit. is first set up. This procedure, once carried out, also provides a basis International spectrum management 26/9 SATELLITE A SATELLITE B Y GHz INTERFERENCE INTERFERENCE MODE 5 MODE 6 Y GHz Y GHz X GHz X GHz X GHz EARTH STATION A EARTH STATION B Figure 26.4 Interference modes from satellite network A to satellite network B, both using frequency band X for down-links and band Y for up-links. Interference from network B will enter network A by similar modes (Wanted signal paths are shown in boken line) for co-ordination of subsequent significant changes of frequency modes (modes 5 and 6 in Figure 26.4) between any pair of satellite assignments to both services in the vicinity of this earth station. networks. There may be three other bi-lateral interference modes The procedure (ITU, 