27.405 MHz
Channel 40 sits at 27.405 MHz and is used mainly for ssb — trucker ssb overflow from ch.19. Like most of the 40-channel band, exact usage varies by region and time of day — the best way to know what a channel is used for near you is to listen before you transmit.
This channel is in the SSB segment: up to 12 watts PEP on single-sideband is legal, versus 4 watts on AM. No license is required either way.
All 40 CB channels are fixed nationwide by the FCC between 26.965 and 27.405 MHz. Channel uses like the ones described here are widely-observed operator conventions, not law — the frequency is fixed, but who's talking on it depends on your region and the time of day.
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