see also:

• remote communication for campers and hikers
• radio basics
• radio for campers
• radio receivers
• hand crank torch radios for disasters and hiking
• bushwalking in Australia
• navigation management for hikers
• getting a weather forecast when camping or off-grid
• radar and radar motion detector sensors for campers
• radio antennas
• radio signal intelligence (SigInt)
• software defined radio (SDR) receivers
• transceivers - software defined radio (SDR)

• 2-way CB radios play a very important role for many 4WDers and truckies
  • they allow communication between vehicles on highways - road conditions, dangers, safety to overtake, etc
  • allow spotters to communicate with a vehicle driver during vehicle recovery operations such as winching, navigating deep track ruts, etc
  • allow 4WD convoys to communicate when driving on remote, and often potentially dangerous roads

• 80 channels on 476-477MHz (~0.63m wavelength)
• channel spacing changed from 25kHz to 12.5kHz in 2011 to double the number of channels from 40 to 80
  • hence channels 1-40 have frequencies starting at 476.425MHz then add 25kHz to get each subsequent channel
  • frequencies for channel x (for channels 41-80) is the frequency for channel (x-40) + 12.5kHz
• all communications on every channel are public - anyone can hear and join in if they are in range
• maximum power is restricted to 5W device outputs
• CB transmissions are time limited to 3 minutes to ensure a channel is not blocked accidentally by a depressed PTT button - CB radios are required to have this feature
• you can use software defined radio (SDR) receivers to listen in on CB radio - usually using narrow FM
• in Australia CB UHF is used instead of General Mobile Radio Services (GMRS) which is what can be used elsewhere such as the US on different frequencies - GMRS is not used in Australia
• legally restricted UHF channels
  • Channel 5 and 35: are the designated emergency channels and are not to be used except in an emergency.
  • Channel 11: is the ‘call channel’ and is only to be used for initiating calls with another person, you should quickly organise another vacant channel to continue your discussion on.
  • Channel 22 and 23: are only to be used for telemetry and telecommand, packet data and voice transmission are not allowed
  • Channel 61, 62 and 63: are reserved for future allocation and transmission on these channels is not allowed.
• accepted CB radio use
  • Channel 10: 4WD Clubs or Convoys and National Parks.
  • Channel 18: Caravanners and Campers Convoy Channel.
  • Channel 40: Australia Wide road safety channel used primarily by truckies and oversized load pilot vehicles.
  • Channels 9, 12-17, 19-21 24-28, 30, 39, 49-60, 64-70, 79 and 80: General chat channels, simplex use.

• Repeater channels in Australia function in duplex mode:
  • eg. the radio transmits on the input channel (33), and the repeater repeats the signal on the output channel (3)
  • if a CB radio is set to channel 3 in repeater (duplex) mode, pressing the PTT (Push To Talk) button causes the radio to transmit on channel 33; the repeater then re-broadcasts it on channel 3 for others to hear
• for example, channel 3 is a repeater input channel
  • if near a repeater site, there will also be short digital bursts that could be telemetry or control packets for the repeater system (eg. keep-alive, access tones, telemetry)
• repeater channel pairings:
  • ch 1 ⇒ ch 31
  • ch 2 ⇒ ch 32
  • ch 3 ⇒ ch 33
  • ch 4 ⇒ ch 34
  • ch 5 ⇒ ch 35
  • ch 6 ⇒ ch 36
  • ch 7 ⇒ ch 37
  • ch 8 ⇒ ch 38
• location of CB repeaters:
  • note the receiver for the paired channel is at the same location as the repeater transmission base station (ie. receiver for Ch33 and the transmitter for ch3 are both at MELO3 in Cranbourne)
  • see https://www.vkham.com/Repeater/uhfcb.html

• Ensure your radio is not being blocked by metal (eg. a towed caravan or metal ute tray box will block radio to and from behind) or trees and the antenna is as high as possible from the ground
• Put your radio into scan mode to see which channels are being frequently used by other people, so you can choose a different channel for your own conversations
• Select the channel you wish to talk on by using the up down arrow keys (note the specific vs general channel uses)
• Wait a few seconds after others have finished speaking in case someone needs to get in with an emergency call
• Hold the push-to-talk (PTT) transmit button on the side of your radio or handpiece,
• position the microphone 5 to 10cm from your face - microphone works best if held forward of your cheek so you talk across the microphone
• wait one second before beginning your transmission - this will avoid your voice being cut off, then talk briefly slower than usual and clearly
• When you’ve finished talking, release the transmit button. Unlike telephone communication, users can’t transmit simultaneously – so always wait for others to finish their message before replying.
• If you are receiving a weak signal, try turning the squelch level down to hear them. Squelch is the function which silences weak or noisy transmission.
• conversation etiquette:
  • if trying to contact Joe use “Hi Joe can I get a Copy”
  • at end of your line say “Over” to indicate you have finished talking - although most don't seem to use this anymore
  • “Over and out” = signing off end of radio transmissions
  • “Roger” or “Copy that” or “10-4” = okay or message received
  • “4-10?” = do you agree?
  • “10-9” = Please repeat I didnt quite hear that
  • “10-6” = Can't talk right now
  • “10-20” or “whats your 20?” = what is your current location
  • “10-51” = I'm heading to you
  • “10-100” = I need a toilet stop
  • “Affirmative” = yes
  • “Negative” = no
  • “Breaker Breaker” or “Breaker One Niner” = you have something important to say to cut in on a conversation or you are about to start transmitting
• Duplex function:
  • helps increase the range of UHF radios using repeater stations set in ideal locations, such as hills. In duplex mode, the fixed position station forwards the signal it receives from repeater input stations 31-38 & 71-78 to the corresponding output stations 1-8 & 41-48.
  • if you are wanting to transmit on repeater channels and there is a repeater station in your vicinity then you must use Duplex mode
• see https://westaussiecampers.com/on-the-road/cb-cheat-sheet/

• uses specific words to represent letters during radio communication, ensuring clarity and accuracy.
• A - Alpha, B - Bravo, C - Charlie, D - Delta, E - Echo, F - Foxtrot, G - Golf, H - Hotel, I - India, J - Juliett, K - Kilo, L - Lima, M - Mike, N - November, O - Oscar, P - Papa, Q - Quebec, R - Romeo, S - Sierra, T - Tango, U - Uniform, V - Victor, W - Whiskey, X - X-ray, Y - Yankee, Z - Zulu
• these were fixed in 1956 after evolving from the Able Baker alphabet which was initially developed from 1942 to standardize the many different versions used in Britain and USA which differed between navy, airforce and others. IN 1944, 52 nations created the International Civil Aviation Organization to oversee civil aviation in peace time, this was headquartered in Qebec and developed the “NATO” alphabet. Their 1st version was the Able Baker version, but this was not ideal for non-English speakers and a new version was sought which could be easily pronounced and recognized by English, French and Spanish speakers.²⁾
  • Germany had its own version which was changed in 2022 to have place names instead of first names of people

• all caravans and RVs should listen to channel 40 while on the road and listen out for truck drivers trying to talk to you, however, change to channel 18 or other agreed channel when having casual chats
• you should warn a large truck behind you if you are planning to suddenly turn off the road
• only one radio will be heard at one time so wait till the air ways are clear before trying to talk
• on Channel 40, keep any conversations brief and to the point, talk clearly and slowly - it is not for chatting on
• there is also some valuable information passed on via Channel 40 like road conditions, animals on the road, car accidents, wide loads ahead, roadblocks to avoid up ahead, speed camera locations and other things of interest.
• see also https://www.truckfriendly.com.au/wp-content/uploads/2021/04/uhf-radio-use.pdf

call Truck on channel 40 “can I get a copy on truck heading ” (S or N bound depending what way your heading on a compass) They will answer “yes mate got a copy” You respond “coming up behind you heading (N or S depending what way your going looking to pass) can you let me know when safe to come around” Truck will respond “copy that” Then when safe he will give a “copy on 4wd safe to come around” and he will flash his right indicator You reply with “copy that coming around now” - just have a look first to check obviously and your mirror to make sure some else isn’t already coming from behind Then just cruise around make sure you accelerate, most truck drivers will slow a little to get you past.“ After you pass, indicate thanking them by using right left right indicators

• NOT useful for emergency communications due to limited coverage
• generally not worth carrying while hiking solo, but can be very useful for group management purposes
• they are popular with 4WD convoys, for groups of hunters, as well as farmers who take one with them when leaving the vehicle as an important safety consideration
• these transmit/receive 80 UHF channels in the range 476.425 MHz – 477.4125 MHz
• these generally are rated for line of sight coverage
  • when hand helds are used inside cars off-road with no metal blocking line of sight, you would probably need a 3-5W unit at 3.5km ³⁾
  • hand helds are less reliable on highways with tall trees around bends for communicating between vehicles more than 1.5-2km but if you stand on the roof of your car it may work at 5km ⁴⁾
  • if you don't want to install a vehicle radio, then a 3-5W handheld (with a clip on wired remote mic so you can move the unit to a line of sight position in the car and you can charge them, and you can get a magnetic aerial for roof of car that will increase range) is workable for 4WD use as long as you have rear window glass if you try to contact someone behind you
  • 0.5-1W hand helds are really only useful around the camp site or for spotting, so avoid them
  • a 5W handheld makes a nice backup in case you snap the antenna on your car radio and they are great for Spotting/Winching or Snatching etc, and have a use when traveling in a tight convoy
    • eg. GME TX6165 5W twin pack with mics, charger, case will cost ~$AU559
    • eg. the GME TX6600 5W twin pack adds channel selector knob, longer antenna, more buttons, and ability to receive only 403-520MHz, only 70g heavier, but is about twice the price and aimed at commercial usage
• 5W is the most powerful you can usually buy and can potentially get you up to 17km line of sight with a good antenna but they are bigger, heavier (~650g each), use more battery power than 2W versions although the GME can be changed to 1W mode to save battery
• you can also get UHF radios with GPS capability such as:
  • GME XRS-660 (see below)
  • the Garmin Rino 750 - this can show each party with such a device the location of other party members whilst allowing 5W UHF radio communication up to 32km line of sight, and a longer battery life than most smartphones especially in cold weather, plus it is USB chargeable so a USB power pack will allow extra usage. Note though that topographic maps are an extra cost ($A99-199) and must be purchased separately for EACH device, and map updates are not free!
• if you need more than 5km or so in range in vehicles then an option is 50W ham transceivers which can get you to 50-100km but you will need to get a ham radio licence

• if frequently transmitting, use the lowest power setting that achieves adequate transmission
• turn off GPS location services if not needed
• avoid frequent scanning mode as it uses ~6x more power than standby mode:
  • Scan Speed: Higher scan speeds increase power consumption because the receiver spends more time actively switching channels and processing signals rather than being idle. Faster scanning means the radio's internal circuitry works harder, which draws more current.
  • Squelch Setting: A lower squelch setting (more sensitive) causes the receiver to open the audio path more frequently, including on weak signals and background noise. This reduces power saving because the radio has to process more audio and signals. Conversely, a higher squelch setting (less sensitive) keeps the receiver quieter and reduces power consumption.
• dim the display

• in Australia, GME is amongst the leading manufacturers of UHF CB Radios for off-roaders
• the XRS range have the most capable features for off-roaders including radio transmission of GPS location
• see GME XRS 2-way CB radio system

• CB radio wavelength is around 63cm and is essentially line of site radio
• antenna length
  • a 15cm hand held CB radio antenna is thus a quarter-wavelength antenna and is usually a unity 2.1dBi antenna and is more omnidirectional and better for hilly or tree areas
  • a 30cm antenna is half-wavelength and provides more gain and is more directional
  • a 5/8 wave antenna (around 37 cm for 476 MHz), is known to provide around 3 dB gain over a quarter-wave antenna because the radiation pattern becomes more focused in a horizontal direction
  • a 60cm antenna is full wavelength and provides even more gain and more directionality but is mainly only useful in open plains
    • a longer antenna concentrates transmission and reception power more effectively along the horizon, extending the range but with trade offs of narrower reception angles, and tuning complexities
• antenna height above ground
  • Mounting height significantly affects the effective gain and range of a mobile CB radio antenna.
  • The higher the antenna is mounted on the vehicle, the better its range and effective gain become.
  • This happens because:
    • A higher mounting position lowers the antenna's angle of radiation, allowing the radio waves to travel closer to the ground over longer distances, enhancing line-of-sight communication.
    • Antennas mounted higher have fewer obstructions (like the vehicle body or nearby structures), leading to better signal propagation and reception.
    • For every 30cm of antenna height gain, an increase of 1.5-2.5 km in range can be expected in optimal surroundings.
    • each additional meter of antenna height can improve signal strength and communication range by roughly 1-2 dBi in open conditions. This gain increase corresponds to roughly 20-50% increase in effective radiated power or received signal strength per meter of elevation. Raising an antenna from 1 meter to 3 meters can bring about 3-5 dB gain improvement overall.
    • Ground types modulate how much increasing antenna height results in improved gain; conductive surfaces (eg. seawater or moist soil) amplify the height advantage, while poor conductivity surfaces (eg. dry soil, sand, or rocky surfaces) diminish it
    • Poor mounting locations can drastically reduce range and reception quality due to signal blockage (especially by metal) or interference.

• these are mostly for in-vehicle CB radios
  • if usage is on open plains with very few obstructions then consider a taller 8.1dBi high gain antenna
    • this will however not work well if there are hills or trees
  • if you are mainly in areas of lots of obstructions then a short 2.1dBi unity gain antenna is generally preferred
  • for intermediate use, jack of all trades, consider a medium height 5.1-6.6dBi medium gain antenna
  • if mounting with protection of a bull bar then the more rigid antennas may be preferred otherwise go for more flexible ones
  • there are antennas designed to be mounted on glass and these may have an internal under glass coupling box with the antenna cable connector
  • many of these use FME connectors
  • if going off road and mounting on a bull bar, esp. with a diesel engine, you will need one with a large spring mount to cope with the damaging vibration
  • most are ground independent antennas so you do not need to screw them into your roof to create a ground plane
  • best to avoid mounting on a bull bar as in an accident they will be more likely damaged mounted there and you will be without comms when you most need it
  • see https://www.youtube.com/watch?v=DfexxrpjIlc
• handheld CB radio antennas
  • most CB radios have a 50Ω SMA male antenna connector hence need a female SMA 50Ω antenna
  • eg. the GME XRS-660 AE4028 antenna is a 15cm long 2.1dBi SMA female UHF Low Band (450-490MHz) with VSWR of 1.9:1 rated for max 5W transmissions
    • for in vehicle use, you could combine with a GME AE4026SMA magnetic antenna base with SMA cable and then paired with a UHF antenna such as GME AE4702B (6.6dBi) or AE4704B (2.1dBi)

• similar to CB radio but different bands
• in the USA, GMRS is allotted 30 frequency channels in the vicinity of 462 MHz and 467 MHz. They are divided into 16 main channels and 14 interstitial channels
  • requires GMRS licence but usually no exam is needed (unlike HAM radio licences)
• in Australia, UHF CB radio fulfils this use

• requires a license to use and not as convenient as CB 2-way radios

• usually use a 100W transceiver
  • ICOM IC-7300
  • YAESU FTDX-10

• eg. Yaesu FC-40

• eg. ICOM IC-AH710 HF Broadband Folded Dipole - 80 Feet Long - 150 Watts

• power supply
• microphone
• headset
• cables
• line filters may be needed

• see remote communication for campers and hikers

• these act like 2-way radios BUT they use cellular networks to send messages - NOT radio
• hence not very useful for remote campers without cellular network coverage