| 摘要 |
<p>The mobile radio system has a frequency allocation plan based on 9 hexagonal areas, each with its own FM channel, grouped together to form a xyz zone. The channels are spaced 20kHz and may be repeated in adjacent zones, no two areas with the same channel being closer than 60km. The number of channels can be increased by replacing some FM channels (1,2,3) with 2 SSB channels each (1-6). The SSB carriers are displaced 5kHz either side of the FM carrier. The lower channel uses LSB and the higher uses USB. Since SSB needs 100km spacing to avoid common channel interference, two zones in which a channel is split into 2 SSB channels must be separated by a zone using that channel for FM. Thus the system operates with a mixture of FM and SSB.</p> |
