What is a UHF CB repeater and how does it work?

Repeaters are a powerful but often misunderstood part of the UHF CB system. Learning how and when to use them can make a massive difference to how you use your CB radio.

What is a repeater?

A repeater is a device which receives radio transmissions and rebroadcasts (“repeats”) them on a different frequency. Repeaters are usually placed in high locations, such as on top of mountains, hilltops or tall buildings, where they can receive transmissions from further away. This also increases the distance at which they can be received, due to higher locations having line of sight further towards the horizon.

By using a repeater, you dramatically increase the range of your radio by using the height advantage of the repeater.

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How do I use a repeater?

Repeaters work by receiving on one channel and rebroadcasting on another. Ordinarily, your radio will transmit and receive on a single channel – this is called “simplex”. When using a repeater, your radio will need to transmit on a different channel to the one that it receives on – this is called “duplex”.

The channel you transmit on is called the “input” channel. The channel the repeater transmits on is called the “output” channel. The input/output terminology is from the perspective of the repeater, not the radio.

Selecting the “duplex” function on your radio tells your radio to automatically distinguish between the transmit and receive channels. There is no need to manually set the input and output channels – merely selecting the correct repeater channel and ensuring the “duplex” function is enabled is all you need to do – the radio takes care of the rest.

What are the repeater channels?

There are 8 repeater channels on 40 channel UHF CB and 16 repeater channels on 80 channel UHF CB. Whilst it is possible to use these channels for simplex communications, it is highly recommended to only use these channels for repeater operation. This is especially true for channels 31-38, as you are unable to hear the output of the repeater, increasing the risk of inadvertently interrupting other users communications.

Duplex ChannelInput ChannelOutput Channel
5 (Emergency Only)5 (Emergency Only)35 (Emergency Only)

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