e locations, where interference to or from used, not necessarily to provide the greatest quantity of radio ser- terrestrial stations may not be serious and conventional frequency vices, but for radio services of the greatest aggregate market value. co-ordination may be quite feasible, although the cost may be He recognises that the establishment of a completely free market in disproportionately high, relative to the value of the facilities pro- spectrum presents special problems and is probably impracticable vided by the VSAT station. However, installation of VSATs at city but he concludes that some substantial application of market forces centre locations is more usual and rooftop antenna mounting would would be beneficial. often be preferred. Spectrally efficient frequency co-ordination be- The use of market forces in this way seems indeed to present tween these city centre VSATs and terrestrial systems operating major problems. Any system which takes authority over radio sys- from city centre towers is often not feasible. tems which can cause international interference out of the hands of The current indications are that the total bandwidth that VSAT governments raises problems, solutions to which are not evident. networks will occupy in the foreseeable future may not be very Also, loss of the benefits of internationally standardised frequency great; a few hundreds of Megahertz may well be ample. If so, the allocation in such areas as mobile communication and radionaviga- best arrangement would be for VSAT networks to be assigned tion would cause widespread difficulties and dangers. Furthermore, frequencies in fixed satellite allocations which are not shared in the it is not obvious that facilities that only radio can provide can earth station locality with terrestrial services. There are few un- properly be denied to society because their market value is small. shared frequency allocations for the fixed satellite service in the However, there are situations where economic pressures of some international table