15 KC splits—A source of channels in the 150 MC band

The implementation of 15 KC split frequencies in the 150 megacycle band is entirely feasible, practical, and in the interest of good spectrum utilization, provided only that sufficient geographic spacing is employed between base stations. Equipment meeting the present FCC standards for narrow-band operation is entirely adequate for this type of operation. With receivers having a two-signal selectivity of 40 db or more at plus and minus 15 KC, the limiting factor on interference range is the side-band envelope of the interfering transmitter. But even with receivers having only 20 db of selectivity at the 15 KC points, 15 KC split-channel operation is clearly superior to co-channel operation. Tone-operated squelch will be even .ore effective in reducing interference with 15 KC spacing between the systems than with co-channel operation because the desensitizing effect of an interfering carrier is reduced by as much as 72 db. Tone operated squelch can be expected to completely eliminate nuisance interference due to voice modulation peaks.