the process of setting up their infrastructure. The impact of the "first Many receiving stations are likewise unlikely to suffer interference come, first served" concept may be particularly serious where from abroad. The national frequency assignment management ar- interference can arise at great distances, typically in the HF fre- rangements described in Section 26.2.1 are adequate for these quency range, 3 to 30MHz, and also where satellite systems are stations. However, interference can cross frontiers; some radio links involved. are international and some radio equipment moves from country to Various special measures have been adopted in particular fre- country and is used wherever it goes. The international aspects of quency bands to deal with these problems and objections. The most frequency assignment management fall into three parts; the interna- important of these measures are as follows: tional machinery for registering frequency assignments is reviewed in this section, the management of spectrum in an international International radio channelling plans have been adopted in a context follows in Section 26.2.3 and the elimination of interference number of frequency bands. These plans specify the carrier if it should occur is considered in Section 26.2.4. frequencies that should be used and the kinds of traffic that they Before an administration makes a frequency assignment, it should should be used for. In some cases they specify also various ascertain whether the activation of the proposed new assignment parameters of the emissions that may be employed. will involve interference with already established foreign assign- International frequency allotment plans have been formally ments. This often involves consultation with other administrations. agreed for some frequency bands. These plans extend the prin- In some circumstances, and in particular where it may be difficult ciple of radio channelling plans, typically by allotting channels to identify the foreign administrations that should be consulted, to 