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CB Information


The CB Radio Service was legalised in Australia in 1977, initially as an 18 channel service on the 27MHz HF band, then soon after also as a 40 channel service on the 476/477MHz UHF band. Eventually the 18 channel HF service was also changed to 40 channels to match the US frequency allocations.

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Upcoming changes to UHF

As of 1 July 2017 the (old) 40 channel band plan (25kHz wideband) will become illegal. At present the old 40 channel and the new 80 channel plans are both legal under the Class Licence, however at the end of June 2017 this will change, and only the new 80 channel plan will be legal to own and use. Why? Because the 40 channel plan consists of wideband modulation, designed for channels that have a 25kHz spacing in between. Under the new plan there is only 12.5kHz between channels, however this can be hard to see.

From channel 1 to channel 2 there is still a 25kHz space, as there is right up to channel 40. However, when you come to channel 41 you find that it sits right between channel 1 and 2, with only a 12.5kHz space either side. This continues all the way up to channel 80, which is only 12.5kHz above channel 40. When ACMA increased the band to 80 channels they didn’t add another 40 channels on top, they added them in between the existing 40 channels! You can see this when you look at the UHF channel chart. This means there isn’t as much space in between the channels, which means the transmit modulation must be reduced, or narrowband.

While some people claim that any radio can be turned into 80 channel narrowband, this is not always the case. Many radios can indeed be programmed with 80 channels at 12.5kHz spacing, but that doesn’t mean they comply with the narrowband specification. The transmit and receive sections must also be changed, as narrowband requires a transmit audio of no more than 10.1kHz, whereas wideband is 16kHz (instantly you can see the issue here, if there’s only 12.5kHz between channels and your signal is 16kHz wide, you will interfere with the other channels AND you will receive interference from them. If the adjacent channel is the emergency channel(s), then you also risk lives).

What to do?

Contact the manufacturer of your radio. The issue is far more complicated than allowing some back yard technician to increase the channels. The radio must be capable of being converted to narrowband mode, AND the manufacturer must have received type-approval for the radio to operate as wide or narrow band mode, otherwise the modification will breach the type-approval and the radio becomes illegal for CB!

More info on CB?

If you want more information about CB, and the protocols to use on CB and on the highway while travelling, look at Glenn Farmer’s book UHF/CB Use & Highway Protocol

Book Review

Glenn contacted ACREM some time ago to request permission to use some of the information on our site in his eBook. Glenn has presented some of the essential information for anyone travelling on our highways and roads - how to converse with the many trucks, and how to use one of the most common communications items among truckies, the UHF/CB Radio. UHF and CB Radio equipment is more common than many believe, and it can be an invaluable source of contact, especially in an emergency.

We welcome the creation of this eBook, and the information it contains. Not only does it provide valuable information about the use of CB equipment, but it also offers car drivers an insight into some of the other communications methods used by truck drivers - indicators and headlights - something that probably confuses many that don’t frequent our highways. I highly recommend this eBook, and trust that it will enlighten everyone who shares the roads with our truck driving friends!

Martin Howells
Chief Commissioner
Australian Citizens Radio
Emergency Monitors Inc.

Purchase the full eBook, or download the free version, at: UHF/CB Use & Highway Protocol

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