e procedure is outlined in Section 26.4.2.5. above. It is broadcasting transmitters or cabled networks. Such earth stations labour intensive but its application is quite feasible given the as- can be sited with due care, in locations which are remote from sumptions for which it was developed, namely that there are rela- terrestrial stations or screened from terrestrial station antennas, tively few earth stations. However substantial numbers of new earth typically by hills or massive buildings. Conventional frequency stations are now being installed, mostly Very Small Aperture Termi- co-ordination is appropriate in such a situation and is in general use. nals (VSATs). The use of frequency co-ordination to manage spec- The second situation has evolved from the use of satellites opera- trum in bands shared by large numbers of stations of both space and ting in frequency bands allocated to the fixed satellite service for terrestrial services is likely to lead to inefficient use of spectrum for distributing television programmes to terrestrial broadcasting sta- one or both services and spectrum management costs may become tions and cabled networks. Large numbers of small receiving an- 26/18 Radio spectrum management tennas are now being used domestically in some countries to inter- Economists point out that radio spectrum is exceptional among cept these signals for home entertainment. In many residential factors of substantial economic importance in that it is available at localities interference from terrestrial transmitters may not be unac- virtually no cost. Levin (1971), for example, argues that in conse- ceptably high, but where interference is strong, there is no practical quence there is no satisfactory mechanism for ensuring that spec- way in which frequency co-ordination can be used to reduce it. trum is distributed between users in an economically optimum way. The third situation concerns VSATs. Some of these earth stations The application of market forces should lead to spectrum being are installed at remot