A new single sideband transceiver for the 27 mc Citizens Band service

Extremely rapid growth of the 27 mc Citizens Band service has resulted in extreme congestion of the allocated 23 channels running from 26.965 mc through 27.255 mc. The majority of these 23 channels are spaced 10 kc and to date, standard amplitude modulated techniques have been employed utilizing 5 watts DC input to the plate circuit of the final RF amplifier stage. Transmission of full carrier and both sidebands is normal in this service. Since there is no reason to believe that additional frequencies will be allocated for the Citizens Band service, a better utilization of the allocated channels must come about if any appreciable expansion in the numbers of licensees is to take place over the next few years. The Mark SSB-27 Transceiver described here is capable of transmitting and receiving on either upper sideband or lower sideband with suppressed carrier on any 5 pre-determined channels of the 23 available. This in effect doubles the available number of channels in the Citizens Band service to 46 from the original 23 since tests have proved that the equipment is capable of providing communications for one system on the upper sideband of an allocated channel with simultaneous communication on an additional system utilizing the lower sideband of the same channel when mobile units of the two systems are operating within one mile of each other. Performance of this nature has been attained through the use of standard single sideband suppressed carrier techniques, excellent frequency stability with all frequency determining crystals contained in a temperature controlled oven, and the employment of a high quality 3 kc single sideband crystal lattice filter.