UHF CB

 (Ultra High Frequency CB Radio)

477MHz CB frequency allocations.
Channel Frequency Channel Frequency Channel Frequency Channel Frequency
1 476.425 11 476.675 21 476.925 31 477.175
2 476.450 12 476.700 22 476.950 32 477.200
3 476.475 13 476.725 23 476.975 33 477.225
4 476.500 14 476.750 24 477.000 34 477.250
5 476.525 15 476.775 25 477.025 35 477.275
6 476.550 16 476.800 26 477.050 36 477.300
7 476.575 17 476.825 27 477.075 37 477.325
8 476.600 18 476.850 28 477.100 38 477.350
9 476.625 19 476.875 29 477.125 39 477.375
10 477.650 20 476.900 30 477.150 40 477.400
Emphasised text indicates special but not common uses, as different uses are emphasised differently.

Channel usages for UHF CB.
Channel Usage
1 through to 8 Repeater outputs.
5 Emergency channel for simplex use, and repeater use where one exists.
11 Calling channel.
31 through to 38 Repeater inputs.
40 Road Channel, for travelling & truckies etc.

Current use of UHF CB in Melbourne.

On 477MHz CB, there is only FM, and a mixture of people are around. Due to the fact that there is only FM you can't differentiate between the real communications enthusiasts and those that just use it for socialising.

Duplex, Simplex & repeaters....What do these mean?

  • Simplex - One way communication only. There is only one transmission and no reply expected.
  • Half-Duplex - Two way communications, however only one transmission at a time.
  • Full-duplex - Two way simultaneous communication. Both stations can talk and receive at the same time. Such as Telephones.

    • On UHF CB when repeaters are used it's termed duplex, and when repeaters aren't used it's termed simplex. So they actually both represent half-duplex transmissions on CB but are used only used to differentiate between repeater usage and non-repeater usage.

    A repeater is a special type of radio, it receives a signal on one channel, but gives it out on another channel. That is why you need 'Duplex' on 477MHz C.B. So you can access the repeaters and make use of them. The C.B will display channel 1, because that is what you are receiving, but if you are using 'Duplex', then you are transmitting on 31 and receiving on 1. That is because the repeater receives signals on channel 31 and re-tranmsits the signals on channel 1. The repeaters are also allowed to be more powerful than just a standard CB, because the purpose of the repeater is to extend communicaion range. Here is a diagram:

    Limit on power.

    UHF CB radios are generally short range radios, and the Australian Government decided to limit the power of the CB radios so people couldn't talk too far and so I suppose there wouldn't be over crowding of the band due to a lot of high powered stations talking. The UHF radios are limited to no more than 5W coming out of the back of the radio.

    Updated on Thursday, April 25, 2002