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CB and UHF Communication


In-Vehicle UHF

 


CB (Citizens Band) Radio

CB Radio provides short-range radio communication.  There is currently no license required to operate.   There are two types HF 27 MHz and UHF 477 MHz.  The MHz (megahertz) refers to the radio frequency on which the equipment operates.

First introduced in 1970, the government initially allocated 18 channels and an annual fee was payable to obtain a license.  In 1982 the band was extended to 40 channels, and in 1994 the government abolished CB license fees.

The Australian Communications & Media Authority (ACMA) announced proposed changes from January 2011 increasing the number of allocated UHF CB channels from 40 to 80.  All the changes are not yet finalised awaiting a second round of comment. Stage two is expected to take effect after January 2016 when all 80 channels will become available for narrow band transmissions.  These changes are expected to provide less congestion.

What some of these changes to the UHF CB channels will mean to you:-

- if you own an old CB UHF radio it will continue to work and you will be able to talk to another person but only if that person is on one of the current 40 channels
- the terms ‘wideband’ will be used to describe older 40 channel and ‘narrowband’ for the newer 80 channel CB radios
- only the new narrowband CB radios will have additional channels up to 80
- channels 61, 62 & 63 will be temporarily unusable
- the sound may be a little distorted using the older 40 channel radios

GME is one company, who make CB radio handsets in Australia, that had anticipated these changes so from December 2010 they commenced building UHF CB radios with the existing 40 channel standard and the new narrowband 80 channel standard.

As of June 2011, GME owners of compatible radios can now operate on the new 80 channel narrow band channels. GME radios that are 80-channel compatible can be easily identified by an ’80 Channel Upgradable’ sticker on the packaging and by the following serial number prefixes. Their website, under ‘News & Events’ 30 May 2011 provides instructions on how to upgrade the UHF CB radio.

When having a conversation always remember CB radio communication is not private.  Also, CB is not like a telephone in that only one person can speak at a time.

For communication in ‘Outback’ Australia it is recommended you buy or hire a satellite telephone or HF transceiver.  See HF Radio article

AM (27MHz) equipment is rarely used these days as it only provided a small range (approx 1- 3 kilometers) and speech was difficult to understand.  Vehicle noise was also a problem. 

A UHF (FM) CB radio provides a clearer communication with less interference from such things as power lines or atmospheric noise.   It uses the 40 channels between 476.425 to 477.400 MHz . 

The UHF CB came of age with the introduction of repeater stations that retransmit signals received on one channel onto another channel.  Channels 1- 8 are designated as repeater output channels with channels 31 to 38 the corresponding designated repeater input channels.  For example, a repeater that transmits on Channel 1 will always receive on Channel 31.

Modern transceivers can scan channels and lock in on a channel when a signal is heard.  UHF communication is often termed ‘line of sight’ communication as good communication is available where there are no obstructions such as hills between yourself and say another vehicle with whom you are communicating.  UHF has a range, in good conditions, of about 20-30 kilometers.  When in areas where repeater stations are installed this range can improve the range up to about 300 kms.

Some brand names of radio transceivers are GME Electrophone, Uniden and Icom.

 

         


 

 

 

 

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Australian UHF CB Radio Channel Information

Recommended Channels:

10 – Used by many 4WD clubs (also known as the outback channel)
12 – Recommended for use by 4WD clubs
13 to 17 – Used for conversations
18 – Recommended for caravanners (although it is often used by road gangs and farmers)
19 – Used for conversation
20 – Used by the Campervan and Motorhome Club of Australia (CMCA)
24 to 30 – Used for conversations
39 – Used for conversations

40 – Road channel – mainly used by trucks (the language can be ‘colourful’), but many 4WD'ers and caravanners monitor or use this channel when travelling on the highway.



Legal Channels:

5 –  Emergency channel (simplex and duplex)
35 – Reserved for emergency use, not to be used in simplex (repeater input)
11 – Calling channel – use to make contact then change to another channel
22/23 – Telemetry and telecomm and only (voice communication is not permitted)
1/31 – Not to be used in simplex when in range of a Channel 1 repeater
2/32 - Not to be used in simplex when in range of a Channel 2 repeater
3/33 - Not to be used in simplex when in range of a Channel 3 repeater
4/34 - Not to be used in simplex when in range of a Channel 4 repeater
6/36 - Not to be used in simplex when in range of a Channel 6 repeater
7/37 - Not to be used in simplex when in range of a Channel 7 repeater
8/38 - Not to be used in simplex when in range of a Channel 8 repeater

 

For simplex communications try to use one of these channels:

9-10, 12-21, 24-30, 39-40

It is best to avoid channels 31-38 completely unless you are sure there isn’t any corresponding repeaters in range.

A simple Google search can be done to locate other web sites that have a comprehensive Australian UHF CB Repeater List.  Further information is also available from the Australian Communication and Media Authority.  UHF CB Australia is also a good website with tutorial videos and latest information.

CB Radio Transceivers

A two-way UHF CB radio is a radio that can receive and transmit messages and the transmitting power must be no more than 5 watts.  It is common for 4WD clubs and RV travellers to have a CB radio in their vehicle or tow vehicle. 

Two-way radios consist of a transceiver, microphone and an antenna (aerial) and operate on the vehicle’s 12V DC power.  The transceiver is normally located under the dashboard or in a purpose designed roof console.  The features of a UHF CB radio vary from make and model but generally have a LCD backlit face panel to view channel numbers, a volume control and scan button to name a few. A co-axial cable runs from the transceiver to the aerial and a thicker co-axial cable is favoured to prevent feedline loss. 

These days dashboards are very cluttered with electronic equipment for remote travel so GME have come up with the GME TX3540 to address this problem by including the LCD screen and all the buttons on the handset.

CB Radio Aerials

Care should be taken in selecting an aerial to suit your purpose as the aerial (or antenna) used will influence the transmitting and reception range and the same may be said for its location on the vehicle.  Larger aerials provide better range and are superior for long distance communications.

There is also a ‘vibration factor’, which can fatigue the antenna, for vehicles with diesel engines as well as road surfaces that needs to be taken into consideration when selecting an antenna.  The fiberglass whip aerial on a medium or heavy duty spring may best suit 4WD diesel engine vehicles and outback travelling.

The aerial should be mounted as high as possible so one mounted say to the roof of the vehicle would provide the best range in comparison to one mounted on the front bull bar as the reception from the rear (behind the vehicle) can be impeded by the vehicle body itself.  However, due to the size of most aerials they are generally located on the wheel arch or bull bar of a vehicle.  Aerials are then connected to the transceiver by coaxial cable.

To ensure equipment is working try calling a ‘radio check please’.


Bull Bar Mount - Wrap Around

Angle Mounting - Roof Rack or Side Mounting

Gutter Mount

Z Bracket - Designed for Bonnet Mounting

 

 

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