CB Radio in The United Kingdom - Methods of Transmission

Methods of Transmission

The originally imported equipment used AM (amplitude modulation) and SSB (single sideband modulation) modes of transmission.

The UK channels that were legalised on 2 November 1981 were on two blocks of frequencies: 40 channels on the 27 MHz band and 20 channels on the 934 MHz band, both of which used FM (frequency modulation) and both unique to the UK. The 27 MHz band frequency allocation is shown here: 27 MHz CB27/81 Bandplan. In 1987 40 additional frequencies were added, which were ironically the same as the U.S. allocation - but again using FM. This additional band is often referred to as the CEPT or EU band. As with the 'old' channels, this band suffered from increased 'skip' reception, especially towards the maxima of the 11-year sunspot cycle.

The illegal SSB mode had its enthusiasts, many of whom lost interest in normal CB and adopted a different style of call-sign (instead of a 'handle') in the manner of radio amateurs. In a related way, some CB enthusiasts took up long-distance communication in a narrow frequency band around 6.6 MHz, using SSB mode. This unofficial 'band' was close to international air travel frequencies and policed more strongly than normal CB radio but reached well into European countries and did not suffer from the high levels of interference on 27 MHz.

Many CB users who witnessed the noisy and unruly conditions on 27 MHz wanted to get away from all that and use the 934 MHz UHF CB allocation. In fact, the cost of cutting edge (at the time) UHF radio equipment meant that only the more serious CB operator would use the band, a nice though expensive haven for mature CB operators, and radio hams who didn't like the 'red tape' of amateur radio. At first the range was limited, but as antenna restrictions were lifted and better equipment started to appear, the number of UHF CB operators grew. Sadly, after just a few years in 1988, it was announced that no more new equipment for 934 would be made, the specification was withdrawn and the band was 'frozen'. Due to the relatively low number of users, the 934 MHz band was eventually discontinued by the government on 31 December 1998. Compared to cheap 27 MHz, the main reason for the lower user numbers on the 934 MHz band, was its cost (up to £500 for a radio), coupled with the fact that by the time reliable Japanese equipment became available in the mid-1980s, most people had opted for the noisier but cheaper 27 MHz, or gone on to take the Radio Amateur Exam. Though many people think mobile phones have taken over 934 MHz, the band remains unused to the present day, and could still be in use for people who spent lots of money on their radio equipment, that still functions perfectly. Arguably, the real reason for the 934 MHz band's demise, was the lucrative sale of the band to the mobile phone industry; the start of a trend that continues with the move from analogue to digital TV.

There are three channels that have a specific use in the UK, though the arrangement is completely unofficial:

• Channel 9: The emergency calling channel
• Channel 14: Calling channel
• Channel 19: Truckers' channel and secondary calling channel

CB users may use the NATO phonetic alphabet and ten-codes.

Nowadays it seems nobody wants to use Channel 14 for Calling, even though Channel 14 was actually intended for homebase users and Channel 19 for mobile users.

Channel 9 was taken more seriously for emergencies in the 1980s, whereas nowadays Channel 9 is just another breaker channel. If anybody was really stuck or maybe in an attempt of being hijacked of their lorry or similar life-threatening situation they should call for help on the most-used Channel, which is 19.