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The '''mesomeric effect''' or '''resonance effect''' in [[chemistry]] is a property of [[substituent]]s or [[functional group]]s in a [[chemical compound]]. The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant [[resonance structure]]s and is symbolized by the letter '''M'''. The mesomeric effect is negative ('''-M''') when the substituent is an electron-withdrawing group and the effect is positive ('''+M''') when based on resonance the substituent is an electron releasing group.
'''CB Radio''' was first introduced into the [[United Kingdom]] in around 1978 (although these dates are hard to confirm accurately). People were using [[CB radio|American Citizens' Band Radios]] and were illegal to own and use. The modes of transmission used were AM ([[Amplitude Modulation]]) and SSB ([[Single sideband modulation]]). The usage of illegal CB radio peaked in 1980 and the UK Government was forced to legalise CB Radio.
*Examples of -M substituents: [[acetyl]] (UPAC ethanoyl) - [[nitrile]] - [[nitro]]
In the run up to legalisation, many people wanted the unused since WW2, vhf bomber frequency for UK CB. This would have offered much better conditions for CB; nice clear channels without the chronic overseas interference there is on 27 MHz. This interference is often so severe, it even stops local contacts from being made, rendering 27 MHz CB totally useless. The fact is that short wave is not the place for short range two way radio; the professionals [Police, Fire Brigade, and Ambulance etc], all use vhf/uhf.
*Examples of +M substituents: [[alcohol]] - [[amine]]
The net electron flow from or to the substituent is determined also by the [[inductive effect]]. It's important to note that the mesomeric effect as a result of p - orbital overlap (resonance) has absolutely no effect on this inductive effect, as the inductive effect is purely to do with the [[electronegativity]] of the atoms and their structural chemistry (which atoms are connected to which).
CB became legal in the United Kingdom in 1981; hence the logo stamped on all type approved radios of this era ''CB27/81 or CB934/81''.
The concepts of mesomeric effect, '''mesomerism''' and '''mesomer''' were introduced by [[Christopher Kelk Ingold|Ingold]] in 1938 as an alternative to the [[Linus Pauling|Pauling's]] synonymous concept of [[resonance effect|resonance]] <ref>''If It's Resonance, What Is Resonating?'' Kerber, Robert C. . J. Chem. Educ. '''2006''' 83 223. [http://www.jce.divched.org/Journal/Issues/2006/Feb/abs223.html Abstract]</ref>. Mesomerism is in this context is often encountered in German and French literature but in English literature the term resonance dominates.
A licence is required to operate a CB Radio. This was at one time available from most major [[Post Office|Post Offices]] within the United Kingdom for a small fee, but is due to be scrapped in 2004. No special test is required.
== External links==
The channels legalised on 2nd November 1981 were on two blocks of frequencies. 40 channels on the 27 MHz band and 20 channels on the 934 MHz band both using FM ([[frequency modulation]]). The 27 MHz band frequency allocation is shown here: [[27 MHz CB27/81 Bandplan|27 MHz CB27/81 Bandplan]]
* IUPAC [[Gold Book]] [http://www.iupac.org/goldbook/M03844.pdf definition]
== See also ==
Many CB users who witnessed the noisy & unruly conditions on 27 MHz, wanted to get away from all that and use the superior 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. The 934 MHz band was eventually discontinued by the government on 31 December 1998 due to low user numbers, though this same argument doesn't affect the huge amount of frequencies that a relatively small number of radio hams can use. The main reason for the public refusing to accept 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 1980's, most people had opted for the noisy and cheap 27 MHz, or gone on to take the Radio Amateur Exam.
* [[List of publications in chemistry#Organic chemistry|Important publications in organic chemistry]]
== References ==
Later on in the 1990s the government allocated an additional 40 channels in line with the emerging European harmonisation and the American channel allocation method, although transmission was still only allowable using FM modulation.
<references />
[[Category:Chemical bonding]]
The 27 MHz band frequency allocation is shown here: [[27 MHz FCC Bandplan]]
[[de:Mesomerer Effekt]]
There are three channels that have a specific use in the UK
* Channel 9 - The emergency calling channel
* Channel 14 - Calling channel
* Channel 19 - Truckers channel and calling channel
CB users may use the [[phonetic alphabet]] and [[ten-code]]s.
===The CB craze and legalisation===
The CB craze in the UK started off with a few individuals, particularly truck drivers, importing US equipment and using it illegally. It clearly served a need as the craze grew rapidly, reaching an enormous peak around [[1980]]. While CB sets from the US had been used in the UK since around 1977, this was still a very small number of users. However, by [[1979]], the widespread existence of illegal CB was becoming common knowledge, especially among the more technically aware. Around this time, companies in Britain started to sell US equipment quite openly, as there was no law against selling or owning a set, only using one. At the same time, technically savvy engineers with a certain amount of curiosity about the rumours, started to convert [[radiotelephone]] equipment to use on the 27 MHz band. The result was an explosion in the number of users, and a huge growth in the CB culture that accompanied it.
While the number of users grew, the authorities were slow to react, but by the beginning of 1980, a number of police forces decided to take it upon themselves to start clamping down on illegal CBers. The normal authority for regulating the use of radio, the Home Office Radio Regulatory Department, were overwhelmed and could not possibly trace and prosecute every illegal user. The fact that the police weighed in to enforce the law is probably one reason why the craze grew and had a more extended life than it might otherwise have done - suddenly there was a common cause (the legalisation of CB) around which CBers could organise. As a result, CB clubs sprang up in most towns around the country, and numbers of users went through the roof. As the fad reached its peak towards the end of 1980, it became impossible to achieve more than a few miles range at most, such was the number of users jamming the channels.
Around this time, a number of CB-related periodicals appeared on the market, and you could buy CB equipment such as antennae in many ordinary car accessory shops. The CB clubs organised a number of national demonstrations in favour of legalisation, including a mass "convoy" to the heart of London, which brought the city to a standstill. In the face of overwhelming support, and the fact that the current situation was unenforceable, the government hastily commissioned a white paper proposing a CB service using the 934 MHz UHF frequency band. Among the enthusiasts, there was an outcry, since they wanted to use the 27 MHz equipment they had already invested in, despite the fact that the band was already allocated for model control and other applications. Eventually the government capitulated, and sanctioned both a 27 MHz and 934 MHz band. The CB lobby was appeased, until they saw the fine print - the new 27 MHz band used an odd channel offset and [[FM]] modulation, so it was incompatible with the American system. The reason for this was on the grounds of reducing as much as possible the interference to legitimate services. By then it was too late, the legislation had been passed, and the 27 MHz FM system was rushed in.
The new system was taken up enthusiastically by all those who had held back using an illegal system, and it was one of the biggest selling gifts for christmas in 1981. Those who had been using the illegal system for the previous few years felt they had been deceived by the government, and there was considerable resistance to the new sets from them. Many did make the change however. The combination of the old and new systems operating on a largely overlapping band rendered both systems more or less unusable, especially in the 6 month period following christmas 1981. With the fight won, albeit with a considerable compromise, and the system practically unusable, the remaining CB clubs gradually dwindled in membership, most disappearing altogether within a year.
===CB culture===
At the height of the craze, everyone was either using CB or knew somebody who did - it is important to realise that this was a very significant movement, in terms of numbers. While essentially a youth culture, CB was enthusiastically embraced by people in all walks of life, young and old, housewives, business people, techies, and of course truck drivers. The cause of legalisation and the community spirit of beating "smokie" and not getting "busted" was very strong. Much of the culture surrounding CB was initially imported from the US, fueled by such films as ''Smokie and the Bandit'', and ''Convoy''. CBers adopted the [[ten-code]] and much of the incumbent US slang, but this rapidly evolved into a distinctly UK-oriented [[lingua franca]].
Everyone was required to have a "handle" - using proper names was definitely out. In addition, at one time the use of slang terms for the most everyday things was considered virtually compulsory. For example, I recall overhearing a conversation in which a CBer invited another round for a cup of tea - after a very long pause with the mike held down following "fancy a cup of....", she finally offered the slang term "mud?" - the use of the everyday "tea" would have been breaking the culture. Another typical aspect of the UK CB culture was the low-level of paranoia that accompanied every conversation - perhaps natural in the light of the fact it was breaking the law. It was forbidden to disclose ones ___location (or "twenty", after the ten-code), but it was OK to give clues in a semi-cryptic form. Presumably any eavesdropper had the same chance of solving these as the intended listener, so the value of this was moot.
There were technical aspects to the culture - for example, very few people had much idea what [[VSWR]] (voltage standing wave ratio) was, but everyone knew their antenna had to be "swred in" before use. Some even referred to this process as "swearing in", as if the antenna had to give its oath that it would broadcast straight and true... The "swring in" ritual was also often part of another huge aspect of the CB culture - that of the "wind up". This involved convincing another CBer to do something on a false premise, usually a form of practical joke. Often this could be witnessed if the victim was within sight of the perpetrator, but was not aware of this. A typical example was to get a newbie to "swr in" his antenna by standing on the bonnet of his vehicle with no socks on, one leg in the air and his hand on the antenna. The perpetrator had to convince the victim that it was enhancing his signal.
The CB channels remained very busy until 2000, when more and more channels became empty as fewer and fewer users were on air. This is due to the rise of pay-as-you-go mobile phones [the ultimate walkie talkie] and flat rate access to the Internet. Amateur radio which gained most of its number from CB radio since 1980, is also in decline.
[[Category:Radio in the United Kingdom]]
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