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CB radio use is widespread, but courtesy and legalities aren't well known.

In February 2017, the Australian Communications and Media Authority (ACMA) very quietly reversed its decision to make 40-channel UHF radios illegal from June 2017. When the 80-channel spectrum was gazetted, 40-channel radios were banned from sale and were to be phased out. Now they’re not.


It is estimated there are thousands of UHF, or citizens band (CB) radios on farms and in trucks, caravans and businesses throughout Australia and upgrading to 80-channel radios was going to cost some businesses tens of thousands of dollars.

The manager of spectrum licencing policy at ACMA, Dominic Byrne, said the two systems are working well alongside each other, so the Authority had decided to remove the requirement for all users to upgrade to 80-channel UHF sets.

“These changes were introduced to manage congestion and interference in the CB radio channels,” he said.

“Based on both some dialogue we’ve had with CB users and some monitoring of the CB channels we’ve been doing … we don’t think that there’s any harm from the continued operation of the 40 channel units.”

Many UHF CB users were upset by the original decision to make 40-channel radios illegal and many more were completely unaware of the need for the change to 80-channel units.

A key trucking industry association has expressed concern over a lack of communication about the revised law from ACMA. The president of the National Road Freighters Association, Tony Hopkins, runs a large firm in Queensland involving 50 trucks.

It would have cost Mr Hopkins’ company $40,000 to buy new communications equipment and he said he could not substantiate the need.

He said he became aware of the changed legislation in March 2017 and he advised his members then.

“We got a response from a lot of the trucking community,” he said.

“They were outraged and couldn’t believe something like this was happening,” he said.

Mr Hopkins said making 40 channel UHF radios illegal was done without consultation with his industry, but Mr Byrne from ACMA said there had been consultation over a long period.

“This is the product of a review we conducted some years ago and there was an extensive consultation process leading up to these changes in 2011,” he said.

“We’ve also made a statement on our website.”

However, OTA agrees with Tony Hopkins on the point that the changed rules were poorly communicated to the CB-using community.


Not so simple

Also, we know from experience with vehicle convoys using a mixture of 40-channel and 80-channel radios there are problems.

While the 40 channel sets will still work, and talk to the mid-sections of the 80 channel band, they pose a real risk of interference with 80 channel band sets and repeaters. Why this happens is very simple.

Forty-channel wide band sets have a channel spacing of 25kHz and transmit a signal that is 16kHz wide (8kHz either side of the channel). When there were only 40 channels this was fine as there was 25kHz between channels, providing a 9kHz buffer.

However, when the 80 channel band was introduced this changed. Because bandwidth remained the same, but  accommodated twice as many channels, there was only 12.5kHz between the old and new channels.

This is a problem when you have a signal on one channel  extending up 8kHz and another signal on an adjacent channel extending down 8kHz. The intermediate channel between those two can be swamped by signals from both sides.

The situation seems to be exacerbated by people not having correct aerials, or using old handhelds in vehicles.


Avoiding interruptions 

Because of its Citizens’ Band nature, CB radio is ‘open’, meaning anything you broadcast or receive can be heard by any receiver on that channel. That’s a good thing, if you’re looking for important information or emergency assistance, but it’s often just a nuisance.

When we get into new road-test trucks these days we turn off the CB radio more often than not, because the rubbish that’s usually broadcast is annoying and distracting.

In tightly controlled radio environments, such as Marine Rescue and the VKS-737 HF network, voice traffic is much less and users are much more disciplined, with protocols that ensure some degree of privacy.

For the CB network, Continuous Tone-Coded Squelch System (CTCSS) doesn’t give you privacy, but can stop your vehicle to vehicle conversation being interrupted by outsiders.

CTCSS triggers an inaudible tone each time you transmit, recognised by a receiver that is switched to receive transmissions that start with that tone. 

It doesn’t make your chat private, but it does cut out unwanted contributions and can be handy if you’re in a truck convoy and don’t want the four-wheelers involved.


Courtesy and legality

The popularity of CB radios means that nearly every bush-travel vehicle has one and this familiarity can breed contempt. There are strict laws governing the use of Citizens’ Band radios and hefty fines or jail time can apply for misuse.

For example, interfering with life and death broadcasts on the designated emergency channels five and 35 can be a very serious offence.

Don’t let kids play with CB radios!

We’re indebted to Duoro, who operate the CB repeater station at the NSW mountain town of Kurrajong, for the below illustration of channels that can be used for general talk communications and those that cannot.

it would be easier for CB users if the usable channels were in a separate block, away from the channels that can’t be used, but that’s not how bandwidth operates, unfortunately.

When the Wide Band 40-channel network was expanded to 80 Narrow Band channels this was achieved by ‘squeezing’ the 40 additional channels in between the existing ones

Channels 41 to 80 are located halfway between each of the original channels – channel 41 is  between channels one and two.

The original 40 channels are now Narrow Band but remain unchanged in their frequencies.

When a NB radio receives a transmission from a WB radio on the same channel, the audio may sound loud & speech distorted.

When a WB radio receives a transmission from a NB radio on the same channel, the audio will be quieter compared to a WB radios transmission.

When using a WB radio on channel 10 and a NB radio is using channel 49 or 50, which are adjacent to channel 10, the WB radio will hear the NB radio as distorted and off frequency, where a quality NB radio will not open its squelch to the WB radio.

Note that you can use channels nine to 30; 39 and 40; 49 to 70 and 79 and 80 for general talk communications in simplex mode (talk and receive     in one-voice-at-a-time succession) and channels 1-8 and 41-48 for repeater-created duplex mode (telephone-like talking). To access duplex mode you select it and the display will show DUP, RPT or a repeater icon.

Channel 10 is the common 4WD communications channel.

Etiquette dictates that Channel 11 is a call channel only, so after making contact on that channel, move to another one for conversation.

Channel 18 is the preferred caravan communications channel.

Avoid using Channels 29 and 30 in some areas, because they’re used for information broadcasts.

Channel 40 is the truckies’ channel and is often filled with obscene language, unfortunately. However, you can use it to talk to the driver of a truck you’re planning to overtake.




























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