27MHz or HF CB is possibly best known from movies such as Smokey and the Bandit and Convoy. This band utilises equipment with 40, 23 and 18 channels. 18 channels (known as “Australian”) was the original allocation legalised in 1977, while 40 channels was the band legalised when the class licence was introduced and was the same as the 40 channels used in the USA at the time. 23 channels was used in the USA at the time of legalisation in Australia and, although illegal, was used in Australia prior to 1977. 23 channel sets use the first 23 channels of the 40 channel allocation.
With the exception of channels designated for a specific mode/use (e.g. call channels), the modes (AM/SSB) shown under “Modes/Use” are by way of a “gentleman’s agreement” that came in before CB was legalised (and inherited from the USA.) Other than the call channels (11 and 16) any mode can legally be used on any channel, however in the interests of peaceful coexistence between AM and SSB operators the bandplan shown is strongly suggested. Also, the frequency does not always match the channel number until channel 25 and above, and the frequencies for channels 23 and 24 are out of sequence due to early equipment design.
|Ch. (23/40)||Ch. (18)||Frequency||Use (legal)||Modes/Use*|
|8||4||27.055||General use||AM – Road channel|
|9||5||27.065||EMERGENCY||AM and SSB|
|35||—||27.355||General use||LSB long distance calling|