Land mobile SSB : Promises and problems

SSB radios for land mobile use will require more circuits and tighter tolerances than FM units. The extra circuits, which are required for purposes such as pilot extraction and automatic gain control, must be designed as compromises between various aspects of performance and cost. Tests, with phase-locked-loop receivers, of three pilot schemes (pilot carrier, tone-in-band, tone-above-band) have given very similar results. Considerations of the ease of implementation, and compatibility with existing systems, suggest that pilot carrier is to be preferred. Amplitude companding may improve the effective signal to noise ratio under some conditions but its use is optional, not essential.