In The Beginning....

CB Radio goes back much further than many people will imagine. CB stands for Citizens Band and it started life in America governed under the FCC, (Federal Communications Commision) way back in 1945 where it put aside some frequencys for Public use.
The FCC is a federal agency that regulates electronic communications such as the radio, TV, Phone, Internet and so on. They chose the lowest frequency spectrum at that time leaving other frequencies for more important uses (police, military, radio and TV) and also because they thought long distance communication couldnt occur on these frequencies....

On July 3rd 1958 the FCC (Uncle Charlie) officially assigned 27MHz for the use of CB radio with 23 channels on AM (Amplitude Modulation). Back then it was known as the Citizens Radio Service and to talk on it you had to obtain a licence by filling out a simple form but this was later eliminated. In 1977 the FCC assigned 17 more channels thus making it 40ch and the Phase Lock Loop came into its own.
Earlier CB's used to have a crystal for each channel making them very bulky and was controlled by a rotary dial (cooker dial) and they were limited to 4w ERP (Effective Radiating Power) .
With 40 channel CBs came the PLL (Phase Lock Loop) which did away with nearly all these crystals making the sets much more stable and smaller and the frequencies needed for the channels were mixed together and controlled by a rotary channel selector with a LED (light emitting diode) display.
Then came SSB (Single Side Band) which worked by using the same frequencies but making each channel available in two different modes eliminating the need for a carrier signal needed by AM, making the channel 3 times larger AM, USB,LSB. With the AM carrier removed on SSB more power could be concentrated into the transmission increasing its talking distance over that of AM.

CB in the UK

CB began to take off in the UK in the Mid 70's thanks to such films as smokey and the bandit, Convoy, Dukes of Hazzard and CB magazines like Citizens Band and Breaker on the Side, ect. and it was the cool thing to have an Illegal CB and non-suss antenna (Unless you were brave or stupid) and many left it till late at night after the tellys closed down (Yes they used to go off air late at night no 24 hr telly then) .Why wait?? because AM radio's used to Rip into black and white and old colour TVs like you wouldnt believe and also interfere with Phones.... and even model planes... something had to be done....the DTI and radiocommunications agencys were hot on our heels (Buzby).

After much protesting and mayhem caused by marchers and pressure on the government of the time The then Home Secretary "William Whitelaw" brought us the legalised version (2nd November 1981) of CB radio still on 27MHz but higher up the band and FM (Frequency Modulation) instead of AM. These FM rigs caused a lot less interference than their AM counterparts and instead of the 9 to full scale of interference on the "mid" block (Original 40ch) we had a much quieter, more useable in the day service. Another difference with the new FM sets was the FM white Noise (hiss) which was bloody annoying compaired to the Quiet AM background noise (At Night) but this is where the Squelch came into its own... Longer distance copies were clearer on FM  and distance noise under the FM carrier was eliminated completely leaving a nice clear signal. On AM you could hear other stuff in the background even if it was a much weaker signal to the person you were talking to. (This is also why most music radio channels went on the FM network)

CB radio was the thing to have, millions were sold in the UK, some were complete pants and had terrible broadband rejection, some were very good and had loads of fancy switches and knobs. Antennas were restricted in height to 1.5m and 4w output as previous. Many people complained this FM CB would be useless and have no distance to it but they were proved wrong. All the 40 channels were full especially in the big cities, and people campained for more channels to use as it was vastly overcrowded.

A CB licence was (and still is) required at 10 for the year (15 now) which was small potatoes realy for the amount of entertainment they gave, and many people made new friends and even got married thanks to the CB radio..... yes it was great !!.

There was (is) another frequency used by UK Citizens which isnt talked about much. It is the 934 MHz system. These radios operate between 934.0125MHz to 934.9625MHz (20ch, 50KHz spacing instead of 10KHz) but were never highly used due to the fact they were very expensive, even the accessories were dear making it an "elitest" band... missing the point of CB entirely. These radio's are no Longer made and are illegal to use since 1st January 1999. These radios are marked CB934/81

In the early 90's the Government allowed us the PR27GB band which was the original 40ch from the 70's but still on FM. You had to have one CB for each Band, converting the radio to work on both blocks was a no no..

The law was relaxed on Antennas too so you could legally use a half wave (18ft) or 3/4 wave (21ft) silver rod or the like, maximum width 55mm not including any groundplanes, increasing distance tremendously.

Then came the PR27/97 (December 1997) which legally combined FCC FM and UK FM for the first time, which came a bit late really as the hobby had already dwindled quite a bit. Still, it gave us extra channels to escape from some of the "Muppets" who had no real interest in the hobby but bought a complete straight 40 setup for a tenner and found great amusement by threatening people and playing music over it... such losers !!

1999 saw the release of PMR446 which a few people are getting into but these are only really designed for local work and although possible, DX is more luck than planned. You can only use handhelds with a fixed antenna and 0.5w (500mW) output. The plus point is there is NO LICENCE required for this and the radios themselves are inexpensive unless you go top of the range. Not quite CB but not far off. Its use is for private and professional alike.

Recent events

For a couple of years now weve heard rumours about the UK27/81 band being de-regulised and the frequencies taken away from CB use.  Also we were told we would no longer need a licence and the band would be phased out soon after 2010. Ive also heard rumours that AM and SSB might become legal but I think thats more wishful thinking than anything else.
Next we were told about  sharing the band with
CADS (Community Audio Distribution System) which has been running on a trial basis for a few years now,  which involves churches transmitting their sermons on the UK27/81 band (they would be licensed of course) and the results of that pilot will no doubt be reaching us soon. In the meantime there is no Hard and Fast  legislation yet as to what will happen.

So... at the moment both bands are still legal to use with the correct equipment and a licence is required at
15 per year. Youngsters and pensioners get it free.

Latest

December 8th 2006. CB radio has now been de-regulated so you no longer need a licence to use CB radio. This does NOT mean you can use anything you like. It works the same as PMR446. No licence but the correct type of radio equipment will still be needed. Anything converted will NOT be allowed.
UK27/81 radios are no longer made and the type approval has been withdrawn. Ofcom, however, have said that UK27/81 equipment may still be used for the radios useful lifetime. This can mean virtually anything as CB's can work without problems (If correctly used) for many years. Until another piece of legislation emerges in the future then it is business as usual as far as these type of radios go.

More information, if required, is available on the Ofcom website.

Some reading for you..
DEREGULATION OF CITIZENS BAND RADIO AND EVENTUAL WITHDRAWAL OF THE UK40 ONLY CHANNELS
SUMMARY OF CONSULTATION RESPONSES AUGUST 2003

!! PEOPLE WHO DO NOT HAVE A VALID CB LICENCE DO GET BUSTED !! (SNIPPIT FROM 2000)

THE COMPLETE STORY BEHIND THE LEGALISATION FIGHT FOR CB IN THE UK. (LONG READ BUT ITS OUR HISTORY )
whole website here