40 channels on the 27 MHz band and I am not sure, but there was also 20 channels on the 934 MHz band, both of which used FM, but not sure about the 934 now.
Re Dipole..
Antennas for 27 MHz CB
The following types of antenna are legal:
A single, vertical, omnidirectional monopole, the driven element of which does not exceed 6.95m in length or 55mm in diameter, including any loading coils and associated circuitry and casings, but excluding any plates, radial wires or rods designed to act as a ground plane or counterpoise, which are located at the physical base of the antenna; and
A single, vertical, omnidirectional dipole antenna not exceeding 5.55m in length.
Please note that the use of a loop, yagi or any type of beam antenna is prohibited.