Splitting the 450-MC channels

A recently released FCC Notice of Proposed Rule Making, Docket No. 13847, contains a proposal to subdivide the existing 50 kc channels in the 450-470 mc private land mobile band into twice as many 25 kc channels. Field and laboratory tests conducted to date indicate that the proposed technical standards can be successfully implemented in closely controlled test systems. Some significant problems may arise in actual "user" systems, however, if transmitters and receivers are not properly netted and held to a close RF channel tolerance. Considerable attention must be given to the various factors which determine the amount of receiver performance degradation experienced, if successful implementation of "same area" adjacent channel operation is to be achieved. Existing 450 mc equipment of recent manufacture should provide adequate performance in most systems until the 25 kc split channels are assigned to new users in the same area.