UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia, New Zealand, Vanuatu, and Malaysia in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels (16 output, 16 input) allocated to repeater stations. It is similar in concept to 27MHz CB Radio in the United States, Australia, and New Zealand.
Class Licensing means that users do not have to apply for a license or pay a license fee however they must comply with the regulations of the class licence. 
User equipment designs are similar to commercial land mobile two-way radio except the maximum legal output power is 5 Watts. External antennas are permitted and commercially manufactured antennas have gains as high as 12dB. Handheld transceivers (walkie talkies) are permitted and have transmit power from 500 mW to 5W (full legal power) and are relatively cheap compared to full-sized transceivers.
It is illegal to use non-standard radios purchased from overseas because they interfere with licensed land-mobile services. This includes overseas personal radio service devices because they do not share the same band plan, power output and channels as UHF CB. Care must be taken when importing radios from overseas to ensure they comply with local regulations. Approved radios are identified by an Australian standards C Tick usually found on the tag or sticker of the radio.
Many UHF CB radios allow the user to scan channels to find a conversation. Several different scan modes may be provided:
Open Scan scans all 80 channels to find an active conversation. Some radios allow skipping selected channels when scanning.
Group Scan scans a small number of selected channels. For example, a caravanner travelling around the country may choose to group scan Channel 40 (Road Channel), 18 (Caravan Channel) and 5 (Emergency Channel) so they will hear any conversations relating to their travels.
Priority Scan allows selection of a "Priority" channel whilst scanning a handful of selected channels. This could be useful in a convoy of cars where vehicles can set their own convoy channel as a priority channel whilst scanning the designated road channel for traffic updates, if a member from their convoy speaks, the radio will always switch back to the priority channel even if someone is speaking on another channel.
Selective calling (Selcall) allows a radio to call another radio using a sequence of tones, usually presented to the user as a series of 5 numbers. UHF CB radios can be set to be completely silent until they receive a series of tones matching a pre-programmed sequence. Radios which have this feature usually indicate that a call has been received by emitting a number of beeps and by opening the squelch. The popularity of selcall has dropped since the introduction of CTCSS.
Continuous Tone Coded Squelch System (CTCSS) allows a group of radios set with the same tone to converse on a channel without hearing other radios using that channel. CTCSS can be used to silence a radio until another radio with the same tone transmits. This allows monitoring of a channel for transmissions from radios set with the same tone without hearing other conversations that use different or even no tone.
The use of CTCSS is not permitted on UHF CB repeaters or the designated emergency channels.
Repeaters extend the range of transmission by receiving and automatically rebroadcasting a transmission using an antenna located in a high location, normally the top of a mountain, tall building or radio tower. Sometimes a transmission range of over 100 kilometres (60 miles) can be achieved through the use of a repeater. Repeaters are on channels 1-8 and 41-48 and the duplex button should be pressed to access the repeater.
It is common practice to install signs at the rear of campervans & caravans, worksites, roadworks, some regional highways & National Parks and Heavy Vehicle Checking Stations to advertise a UHF channel to communicate on. For example, during the widening of the M1 Pacific Motorway between Sydney and Newcastle contractors installed "UHF 29" signs at the entry point to each worksite.
Legally restricted channels
The following channels are legislated as a part of the ACMA UHF CB Class Licence.
- Channel 5 and 35 are the designated emergency channels, and are not to be used except in an emergency. To make an emergency call, switch your radio to Channel 5 with duplex on, if there is no response, try again with duplex off.
- Channel 11 is the 'call channel' and is only to be used for initiating calls with another person, who should quickly organise another vacant channel to continue their discussion on.
- Channel 22 and 23 are only to be used for telemetry and telecommand, packet data and voice transmission are not allowed.
- Channel 61, 62 and 63 are reserved for future allocation and transmission on these channels is not allowed.
Channels used by consensus
The following channels are not legislated as a part of the class licence however are used for the following purposes by consensus.
- Channel 10 is typically used by 4WD clubs when in a convoy & in national parks. This channel is used to avoid interfering with road safety communications on channel 29 or 40. If you are not in a convoy it is recommended you use 29 or 40 depending on the road you are using.
- Channel 18 is the campers and caravan convoy channel, typically used by travelers.
- Channel 29 is the road safety channel on the M1 Pacific Motorway and Highway between Brisbane (QLD) and Sydney (NSW). It is used so that users of these roads only hear conversations related to the highway and not unrelated conversations in built up areas. Once leaving the highway, trucks switch to channel 40. It is recommended to avoid using this channel on the east coast unless your conversations relates to road safety communications on these roads.
- Channel 40 is the primary Road safety channel Australia-wide, most commonly used by trucks including pilot/escort vehicles for oversized loads.  
Users should be aware that UHF CB channels 31 to 38 and 71 to 78 are the 'input' channels for repeaters. Users should avoid using these channels to avoid interfering with repeaters. If you wish to use a repeater, switch to 1-8 or 41-48 and press the duplex button.
UHF CB band plan
Expansion to 80 channels
On 27 May 2011 the channel spacing on UHF CB was changed, allowing the band to expand from 40 channels to 80 channels. Due to data channels 22 and 23 occupying 25 kHz bandwidth, the expansion effectively allows the use of 77 channels, as channels 61, 62 and 63 are reserved.
Current UHF CB band plan (80 Channels)
General chat channels are used in simplex mode, repeater channels must be used in duplex mode. If you are not using a repeater it is recommended to choose a "General Chat Channel".
|Channel Name:||Frequency:||Purpose:||Frequency Spacing:|
|Channel 1||476.4250||Repeater Channel||12.5 kHz|
|Channel 2||476.4500||Repeater Channel||12.5 kHz|
|Channel 3||476.4750||Repeater Channel||12.5 kHz|
|Channel 4||476.5000||Repeater Channel||12.5 kHz|
|Channel 5||476.5250||Emergency Repeater Output||12.5 kHz|
|Channel 6||476.5500||Repeater Channel||12.5 kHz|
|Channel 7||476.5750||Repeater Channel||12.5 kHz|
|Channel 8||476.6000||Repeater Channel||12.5 kHz|
|Channel 9||476.6250||General Chat Channel||12.5 kHz|
|Channel 10||476.6500||4WD Clubs or Convoys and National Parks.||12.5 kHz|
|Channel 11||476.6750||Call Channel||12.5 kHz|
|Channel 12||476.7000||General Chat Channel||12.5 kHz|
|Channel 13||476.7250||General Chat Channel||12.5 kHz|
|Channel 14||476.7500||General Chat Channel||12.5 kHz|
|Channel 15||476.7750||General Chat Channel||12.5 kHz|
|Channel 16||476.8000||General Chat Channel||12.5 kHz|
|Channel 17||476.8250||General Chat Channel||12.5 kHz|
|Channel 18||476.8500||Caravanners and Campers Convoy Channel||12.5 kHz|
|Channel 19||476.8750||General Chat Channel||12.5 kHz|
|Channel 20||476.9000||General Chat Channel||12.5 kHz|
|Channel 21||476.9250||General Chat Channel||12.5 kHz|
|Channel 22||476.9500||Telemetry & Telecommand Only (No Voice & Data)||25 kHz|
|Channel 23||476.9750||Telemetry & Telecommand Only (No Voice & Data)||25 kHz|
|Channel 24||477.0000||General Chat Channel||12.5 kHz|
|Channel 25||477.0250||General Chat Channel||12.5 kHz|
|Channel 26||477.0500||General Chat Channel||12.5 kHz|
|Channel 27||477.0750||General Chat Channel||12.5 kHz|
|Channel 28||477.1000||General Chat Channel||12.5 kHz|
|Channel 29||477.1250||Road safety channel Pacific Hwy/Mwy between Brisbane (QLD) and Sydney (NSW)||12.5 kHz|
|Channel 30||477.1500||General Chat Channel||12.5 kHz|
|Channel 31||477.1750||Repeater Input||12.5 kHz|
|Channel 32||477.2000||Repeater Input||12.5 kHz|
|Channel 33||477.2250||Repeater Input||12.5 kHz|
|Channel 34||477.2500||Repeater Input||12.5 kHz|
|Channel 35||477.2750||Emergency repeater input||12.5 kHz|
|Channel 36||477.3000||Repeater Input||12.5 kHz|
|Channel 37||477.3250||Repeater Input||12.5 kHz|
|Channel 38||477.3500||Repeater Input||12.5 kHz|
|Channel 39||477.3750||General Chat Channel||12.5 kHz|
|Channel 40||477.4000||Road safety channel Australia Wide||12.5 kHz|
|Channel 41||476.4375||Repeater Channel||12.5 kHz|
|Channel 42||476.4625||Repeater Channel||12.5 kHz|
|Channel 43||476.4875||Repeater Channel||12.5 kHz|
|Channel 44||476.5125||Repeater Channel||12.5 kHz|
|Channel 45||476.5375||Repeater Channel||12.5 kHz|
|Channel 46||476.5625||Repeater Channel||12.5 kHz|
|Channel 47||476.5875||Repeater Channel||12.5 kHz|
|Channel 48||476.6125||Repeater Channel||12.5 kHz|
|Channel 49||476.6375||General Chat Channel||12.5 kHz|
|Channel 50||476.6625||General Chat Channel||12.5 kHz|
|Channel 51||476.6875||General Chat Channel||12.5 kHz|
|Channel 52||476.7125||General Chat Channel||12.5 kHz|
|Channel 53||476.7375||General Chat Channel||12.5 kHz|
|Channel 54||476.7625||General Chat Channel||12.5 kHz|
|Channel 55||476.7875||General Chat Channel||12.5 kHz|
|Channel 56||476.8125||General Chat Channel||12.5 kHz|
|Channel 57||476.8375||General Chat Channel||12.5 kHz|
|Channel 58||476.8625||General Chat Channel||12.5 kHz|
|Channel 59||476.8875||General Chat Channel||12.5 kHz|
|Channel 60||476.9125||General Chat Channel||12.5 kHz|
|Channel 61||Reserved for Future Expansion||-|
|Channel 62||Reserved for Future Expansion||-|
|Channel 63||Reserved for Future Expansion||-|
|Channel 64||477.0125||General Chat Channel||12.5 kHz|
|Channel 65||477.0375||General Chat Channel||12.5 kHz|
|Channel 66||477.0625||General Chat Channel||12.5 kHz|
|Channel 67||477.0875||General Chat Channel||12.5 kHz|
|Channel 68||477.1125||General Chat Channel||12.5 kHz|
|Channel 69||477.1375||General Chat Channel||12.5 kHz|
|Channel 70||477.1625||General Chat Channel||12.5 kHz|
|Channel 71||477.1875||Repeater Input||12.5 kHz|
|Channel 72||477.2125||Repeater Input||12.5 kHz|
|Channel 73||477.2375||Repeater Input||12.5 kHz|
|Channel 74||477.2625||Repeater Input||12.5 kHz|
|Channel 75||477.2875||Repeater Input||12.5 kHz|
|Channel 76||477.3125||Repeater Input||12.5 kHz|
|Channel 77||477.3375||Repeater Input||12.5 kHz|
|Channel 78||477.3625||Repeater Input||12.5 kHz|
|Channel 79||477.3875||General Chat Channel||12.5 kHz|
|Channel 80||477.4125||General Chat Channel||12.5 kHz|
Currently, older 40 channel radios may still use 25 kHz spacing however this may be phased out by 2017. The ACMA plan to review this policy in 2016.
New Zealand offers a similar PRS service. New Zealand's Personal Radio Service (PRS) and 26 MHz Citizens Band radio are very similar to Australia's UHF Citizens Band and 27 MHz Citizens Band services.
The New Zealand Governments Ministry Of Commerce introduced the UHF PRS in 1996 to allow for freely available short-range wireless communications outside the 26 MHz CB band. The UHF (but not VHF) band was selected due to its ability to withstand atmospheric and groundwave interference unlike the existing 26 MHz allocation.
NZ PRS channels
- VMB4 Newcastle - An example of an Australian UHF CB Repeater
- Jim Sinclair Radio Signal Finding McGraw-Hill Professional, 2000 ISBN 0-07-137191-5 page 281
- http://www.uhfcb.com.au/CB-Radio-History.php CB radio History
- Radiocommunications (Citizen Band Radio Stations) Class Licence 2002 - The Australian official license under which UHF CB operates
- Australian Communications and Media Authority - The Australian regulator of the radio-frequency spectrum
- Tropinet UHF CB Repeater Database for a listing of repeaters in Australia.