What channel do you use when you talk on a cb radio?

Answer 1

There are 40 CB channels defined in roughly the band between 27 and 28 MHz,
and another few somewhere near 49 MHz.

UK is 27MHz FM (not on US channel spot frequencies) and 934 MHz FM. AM CB is not approved.

Answer 2

Most any channel. Some GRMS channels that allow 2 or more watts of transmitting power require a FCC License ($75 for 5 years).

Channels 1-7 and 15-22 require a license.

Answer 3

Channel 19 is the most commonly used, although 17 tends to be more common in California.