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CB Radio

Car 2 Car Comms - getting started

Introduction

CB-Radio, well, its kind of 'naff' isn't it. A bit like the 'Rubber-Duck' it makes you think of. But, CB Radio has been legal for a while now, and can be quite useful to 'off-roaders'. If you have a small convoy of vehicles, CB lets you talk between cars, which can be quite helpful, if cars get split up, say by traffic lights, or if one gets stuck or to find out why every-one has stopped, or just to comment on the scenery or the land marks as you are going along.

So, it bears a thought, if you are thinking about green-laning. You don't need to be a die hard, out every week-end off-roader, for it to be worthwhile. A lot of keen green-laners have CB's and use them, and if you are new to it all, having one can mean that you can talk to them and they can let you know what's going on as it happens, and you'll have more confidence from being 'in the picture' as it were.

This article's been up a few years now, and in the make-over I have taken the opportunity of updating it a bit. First of all to tell you a bit about Radio itself, and other types of Radio, and how CB fits into with the other types, and what alternatives they are, before talking about choosing, setting up and using a CB if that's what you want to do. But mainly because the CB Radio 'licence' has now been abolished!

Radio Standards

In the UK, the 'RA' & 'OFCOM' are the government appointed agencies that regulate the air waves; it would be a bit confusing if every-one started transmitting ad-hoc, and people would be distorting other peoples signals and it would all not be very helpful to every-one. At least that's the theory; seems it also gave an opportunity for the government to claim proprietarily rights over the air waves and decide they could 'sell' the rights to use them!

Which is where TV licences come from, and the notion we no longer need a licence to operate a CB; very generously, that bit of the air waves that CB radio works in they have decided we can have for nothing. There's another bit of the air waves we can have for nothing, and that's 'licence exempt' which any-one can use for anything from garage door openers, to remote key fobs, to radio controlled models and kids toys.

However; in order to minimise the possible interference from unregulated use by a multitude of people, they have imposed stringent transmitter power limits; in the case of CB radio, that is 4w transmitter power; in the case of licence exempt radio it's 250mW or 1/4 of a watt.

Rest of the broadcast spectrum of air waves is carved up and allocated or sold off for other purposes; military communication, weather satellites, mobile telephones, TV broadcast, commercial radio stations etc etc etc. Which are all on frequencies, you and I the general public cannot broadcast on.

Others we might are commercial radio (as opposed to commercial broadcast radio) which is the frequencies used by taxi drivers, security guards, and people organising large events and things. We actually use commercial radio for motorcycle training for bike-to-bike communication with students. But, it needs a licence you do have to pay for, and is again restricted to limited transmission powers.

Then there is HAM or Amateur Radio. It is not available to the general public; you have to have a licence, which requires qualifications in radio operation, construction and use, which, once obtained, allows you to broadcast on a much wider range of frequencies and bang out much more powerful signals.

And, I suppose, commercial network, mobile telephones.

Some Tech Stuff

Right, the update has spawned a whole new article; 'Radio - getting technical' over in the theory & know how section; which you may like to have a look at, but summing it up:

Licence Exempt 'Toy' Radio

Before looking specifically at CB Radio, I want to take a little look at the alternatives; and the most accessible form of radio is licence exempt.

This operates on one of the higher frequency bands and is limited to a very small transmission power, 1/4 Watt or 250mW. Any one can operate licence exempt radio equipment, and for almost any purpose; provided it meets the legislative standards. But, it is very short range, and there's a lot of 'traffic' on these frequencies.

Everything from kids Radio Controlled cars, to garage door openers; car remote key-fobs; baby minders, cordless door-bells, that kind of thing, all work on the licence exempt frequencies. Its not great for voice transmission, but it can work and can work acceptably over short range. And it is probably the cheapest and most accessible to get hold of.

10 in woollies, pair of kids 'Action Man' walkie talkies; stick in a pair of PP3 batteries and you are set. Limited range, and a single fixed channel, they aren't very sophisticated; reception quality isn't brilliant, and when the batteries start to go, probably easier to just shout! 

But, between cars in convoy, or for talking to some-one pre-walking and guiding you through a section, or working on the end of a winch, they COULD do the job needed, without any great outlay, effort or hassle.

Without wanting to sound too derogatory of them; yes, they are cheap and cheerful, and though they are sold as children's toys, end of the day, they are still a genuine bit of communications equipment and can be used as such, provided you can work within their limitations and don't expect too much from them.

And actually, some of them are not half bad, and can give a half decent range and reception. Sold in woollies, newsagents and even petrol stations, they are cheap, and cheerful, and dead easy to set up and use. Playing with my kids, we've used toy radio between cars, and I have been surprised at how far an action man walkie talki CAN transmit and how clear you can hear!

OK, so anything more than a half a dozen cars between you it goes all fuzzy, but I can sit in the car and talk to one of my kids in a house three doors down, and across an open field or beach, with a line of sight, talk to one of my kids flying a kite maybe half a mile away. So don't discount them too fast. No great shakes, but might be all you need.

PMR - Personal Mobile Radio

Personal Mobile Radio works in the Licence Exempt range of frequencies, and just like 'Toy' Radio, is restricted to quarter watt transmitter power. But, they work a lot like a hand held CB set and generally have a lot more features, and capabilities.

They usually have 10 channels, numbered from 0 to 9, and often up to nine 'side bands' within each channel, offering up to 99 possible channels for you to talk on. They often have a function for transmitting a 'ring-tone' or 'call' signal to alert another operator to your transmission, and sometimes this can be set with a caller ID so that a transmission from one hand set gives one ring tone, another from a different hand set, gives a different one. Neat, hugh?

In theory though, these shouldn't be any more powerful than Action Man walkie-talkies, as they are restricted to the same transmitter power. But in practice they can almost compete with proper CB in SOME conditions. Main reason for this is to do with the efficiency and sensitivity of the electronic circuits. In essence, they can't transmit any louder, so they talk clearly and they listen carefully, which explains their cost relative to a CB, or an Action Man walkie-talkie. 

A 'toy' radio costs about 10 for a pair, possibly a bit less if you can get one with out a brand name. A single CB  hand held costs about 100. And a PMR will be about 50 for a pair out of the Ingos or Ardex catalogues. Though the prices are coming down the whole while, and you can get PMR's in bubble packs as cheaply as 'toy' radio these days, in places like Aldi or Liddle.

But, take heed, there is Toy Radio, there is Toy PMR, there is PMR and then there is Motorola PMR!

Quality & performance of PMR sets varies hugely, and you really do get what you pay for; and when you buy a pair of PMR sets for not much more than a pair of toy walkie talkies, don't expect them to perform much better; extra cost really is only giving you the extra channels and the fancy ring tones; not the clearer transmission and more careful listening.

I have had experience of a fair range of PMR and I really wouldn't bother with the bubble packed pairs for a tenner as much more than a baby minder or something for the kids on the beach. 30 pairs in the 'average' range from places like Argos are a bit more useful, the features work, their range and clarity is reasonable, but, I found disappointing and no great leap from toy radio or cheap and nasty PMR

If you want PMR that actually starts to offer any real advantage over toy radio, you really have to look at the 30+ a hand set models, where the quality does start to go into making them work like a 'proper' radio, rather than just look like one. But even then, the performance isn't all that great.

Pair in the pic, are Uniden, upper mid range from Argos a couple of years ago. They were the same price as lower specced Motorola's, about 80 I think, with base charger, batteries and hands free kit, which was why I bought them as 'bike-to-bike' intercoms.

As mid range PMR their performance isn't bad; and the range and reception is pretty reasonable, and they do work a heck of a lot better than the cheaper ones. The hands free, voice activation, which is what I bought them for (so they could be used on a bike), lets them down though.

In a car, the range is reduced quite a bit, and practically, they are reaching their limit at about a mile, which is fine if your convoy is close together, but if your last car through gets caught at traffic lights, you might only have a matter of twenty second from getting the car into neutral to tell the lead vehicle to wait for you.

I've occasionally come close to getting a couple of miles range on a pair of PMR radio's, and conversation has been possible, if not easy. Out on green lanes, with trees and hills between vehicles, I've lost any recognisable signal on a PMR in under a mile, Which is where extra bit of muscle CB has starts to become useful

I mentioned that there are four qualities of PMR; budget, which is about as good as toy radio; average; which is a bit better, but not a huge leap, then higher end, where they stop being 'cheap' but do start offering some more realistic performance., but then there is Motorola PMR.

Absolutely no question, Motorola PMR's are about as good as you can get, and the performance from them is pretty impressive.

Where people have suggested that PMR can compete with CB for range and clarity, the ONLY PMR's to come close are Motorola, but they really can only compete with CB under near 'ideal' circumstances. They are still limited to a quarter watt transmitter and a higher frequency range carrier signal, and they just don't have the 'beef' of a CB set with 16 times the power!

I used to have a pair of Motorola's, but they were American spec, operating on a different frequency, and with I think a 1w transmitter. Four times the power, it REALLY made a difference, and I clocked a five mile range between cars with them once, which was pretty impressive, but a UK set wouldn't come close to matching that.

For motorcycle training we use commercial PMR, which look identical, and work the same way, just on a different frequency range, and with I think the 1w transmitter power, like the US spec PMR's. The sets though are expensive, and need a licence, which again costs, so the school tried retail PMR's to see if they worked and could save us a few quid. They were Motorola's, and as good as we could get; but they just couldn't hack it, and the instructors got fed up of having to tear off after students that didn't know they'd lost radio contact, or having students complain that they didn't know what they had been told!

Amateur HAM Radio

I'd better mention Amateur Radio. CB sits between PMR and HAM radio in the hierarchy of things I suppose, and isn't hindered by the limitations on CB of restricted frequency allocation and transmitter power. Other than that; they use pretty much the same sort of hardware; and Radio Ameteurs can transmit on CB frequencies, I believe at a slightly higher power output.

Main impediment with Amateur Radio though is the licensing system, and you have to attend classes to learn about radio operation, construction and use, in order to gain an operators licence, which you have to pay for, and pay an annual fee to renew.

If you are dead keen, it can be a good way to go, to get the extra range and reception CB lacks, or to find 'clear' frequencies no-one else is using. But Current CB usage is so low, there isn't a LOT of traffic out there to bother you.

Only REAL thing worth mentioning here though, is that so far, both 'Toy' Radio and PMR are consumer 'products', self contained walkie talkies or 'transceivers. Everything is in one unit, you put in the batteries and press the button to transmit.

Amateur radio is based on more commercial 'specialist' hard ware, and starts coming in component form, with separate 'base units' microphones, receiver tuners, transmitter amplifiers, modulators, power supplies, aerials and all sorts of techno kit!

Which is why the training and qualification is needed for the licence, because you have to have some idea of what all the stuff is, what it does and how it works to operate it.

CB Radio

OK, finally we get to talk about the actual subject of the article! So, CB radio, can best be described as Amateur Radio simplified for idiots! But, it is starting to look like 'proper' kit, and based on commercial hardware. Just kept simple.

Three 'types' of radio set; base station; mobile; and hand held.

Hand Held, or 'Transceiver' is a big walkie talkie. Much like toy radio or PMR the unit is self contained, and all you need to do is add batteries and press the transmit button. But usually it will have some professional type features like the facility to use an external aerial, or microphone, or power supply.

Mobile 'rigs' are sets not dissimilar to a car radio receiver, usually designed to be mounted on a dash board. They contain the receiver and transmitter, and normally the speaker, in one unit, but have an external microphone and aerial, and are designed to be powered straight from a car's 12v supply.

Base station sets, are intended for fixed installation in a home. There aren't many CB base stations, and most people use mobile sets ran to a large external mast aerial, and powered from a 12v mains transformer. But, there have been fully integrated base stations that run off mains power, and simply have an external aerial feed, or full Amateur component systems, with separate receivers and transmitters, just restricted to the CB frequencies. For our purposes, probably not worth going into much more detail on them; really base stations are the start of Amateur Radio, and not something for fitting in a Land Rover.

So lets look at hand helds and mobile rigs in more detail.

Hand Held CB Radio

As they are an 'integrated' package, you just fit batteries to and switch on, so they are probably a good place as any to start.

On the plus side, that is all you need. They have the full 4w transmitter, and the 40 UK CB channels, and on the latest sets the 40 EU CB channels too. Just like mobile sets, but you don't need to drill any holes in your car to fit them, or mess around trying to find earth and power leads behind the dash, or fitting an aerial & routing the lead. Then, you can transfer it between cars, and even use it away from the vehicle. Sounds ideal.

But they do have some draw backs. First of all, batteries. A hand Held CB, with will often need eight or ten AA batteries, and heavy use can see them spent in a couple of hours. Given more reasonable use, and infrequent transmission, you might see a new set last eight hours of a Green-Lane trip, but you better pack spares, just in case. Or get a car power supply, so that while you are in the vehicle, you can preserve battery life.

The main drawback with a hand held set though is range. To make a set small and compact enough to be easily portable, they make do with a relatively short aerial, maybe not more than six inches long. To improve things a bit, the aerial if often coiled, to give it a longer 'effective' length, but its not brilliant, and put it inside a vehicle and its already compromised size will be masked by the vehicle body. 

You can get an external aerial to mount outside a car that will fit a hand held CB, and you can get battery eliminators, so that you can run them off the cars 12v supply. But, that adds cost, and can have you getting all tangled up in a mess of wires, so not prove too practical.

And there are actually only a couple of hand helds on the market at the moment. Priced at around 100, they could both prove more expensive that a budget mobile rig, even without a host of accessories.

However, they are still useful, and easy to use. The fact that you can carry one around, irrespective of what car you might be in, and don't have to mess around drilling any holes or mounting anything, might make their limitations worth while.

Mobile CB Radio

Biggest advantage over hand helds is the fact that they are designed to fit into a vehicle, so you will have a bigger external aerial, which will optimise the effective range, and it will be wired into the vehicles electrics, so you don't need batteries.

And it should be easy to use in the car, without any untidy power or aerial leads, or without having to find a home for a bulky hand-set etc.

Drawbacks are that it can't easily be swapped between vehicles or used away from the vehicle, and some installation is required.

That said; I know of a number of people who have CB sets that have a cigarette lighter plug on the power leads, and a magnetic aerial base, so that they put the set on the seat next to them or on top of the dash board, stick the aerial on the roof and thread the aerial lead through the door seal.

Mine is shown here mounted in Jaqui's dash just above the radio, which is a natural sort of place for one. Actually, its fitted into one of the air-vent ducts which it conveniently fitted, saving cutting any unsightly holes, or cluttering up the oddment tray, bolting it there.

But what set to go for? Well, the most basic set has:

A lot of sets have microphones with a lot of buttons for functions on the radio. This can be useful if you have the radio tucked somewhere its not easy to get to, but it also makes it easier to press the wrong button, when you hang the microphone up, or whatever, but those are your 'basic' features.

On old sets, tuning might have been done with a tuning knob, and a scale, and you would have to have a chart telling you the frequencies of each channel or a scale marked with the channels so that you could tune your radio in to any particular one. These days though, sets usually have 'PLL' or Phase Locked Loop tuning, which basically means 'electronic' tuning. You just type in the channel number, or press an up/down key to set the channel. This is useful.

Squelch

The last 'basic feature, with a weird name, that people often ask about, so worth a bit more attention, all sets should have a 'squelch' knob, and it's quite important.

Technically speaking, its a tuneable filter. If you have read the Radio Theory article, or remember the mention in 'technical stuff' earlier, the radio receiver receives all transmitted signals, and what it does for you, is separate out the frequency of carrier signal you want to listen to, then filters that carrier signal off the transmission signal

Unfortunately, separating the wheat from the chaff isn't all that easy, and you will normally get some carrier signal distortion left in the audible signal sent to your speaker. That sort of "hasharashaher" noise you used to get when you tuned in an old fashioned TV or Radio.

Turn a CB set on, and you will get the same thing, but what the squelch control lets you do is set a threshold for what it sends to the speaker, so you can block all that out, and unless you have a nice strong signal to listen to, all you get is silence

What you do is turn the set on, and the squelch down so that you can hear all the distortion. Then when some-one starts transmitting, you turn it up so until the back ground goes away.

when you are laning with a group, when you first set out, you'll all agree a channel to talk on, set it, and make a test transmission, so that you can all set your squelch levels.

Thing to remember is that it cuts out any signals of strength lower than you have set it; so its worth setting as low as you can, and maybe putting up with a bit of distortion from time to time, or your set will stay silent, filtering out all but transmissions made from a few yards away at full strength!

Remember the bit about signal degradation; as range increases or the number of obstructions between transmitter & receiver, so the greater the signal degradation; it gets more distorted and weaker.

So, at the limits of transmission range, be that because of great distance or a large amount of obstruction, the signal you are receiving might be so weak, that your squelch will filter it. Turn the squelch down, and the transmission might be weak and a bit hissy, but you could still get something that you could understand

And there are a few of sets on the market now that have back ground reduction features, which are a bit like a fine squelch control, or 'Dolby' for radio! Basically another signal conditioning filter, that takes out back ground hiss, like Dolby was supposed to do for old fashioned audio cassettes

Other Features you might find on sets include some form of bass or treble controls like on an ordinary radio, or sometimes a mic-gain control.

Mic-gain is like a volume control for the microphone. If you have a lot of back ground noise, you turn it down, so the microphone only picks up your voice, not the engine or whatever around you. If you are in a nice quiet cab, you turn it up, and give yourself a bit of extra signal strength.

Not many CB's have mic gain controls, they tend to be auto-levelling or fixed. Apparently it's one of those 'Ham' features that they thinks a bit beyond the uneducated, because apparently messing with the mic gain can cause all sorts of interference problems.

More upmarket are things like 'scan'. What this does is tune briefly between each of the available channels and stop at any that have a strong signal on them. Useful if you are looking for any one-else transmitting.

A similar function is 'Duel Watch'. Basically this lets you listen to one channel, while the set is also tuned to another. If it picks up a signal on the other channel, it automatically switches over and lets you hear that broadcast.

A further refinement on duel watch, is duel scan. This lets you listen to one channel while the set scans through all the others looking for a strong signal. I think you kind of get the idea. There's only SO much you can get a radio to do, but a myriad of permutations on them!

One useful facility some of the basic sets lack, is an external speaker socket. This is a 3.5mm earphone socket, usually on the back of the set, that lets you plug in a jack plug to by-pass the internal speaker to an external one. Some are just a remote speaker, that you can mount somewhere more convenient or audible, and some have amplifiers in to make them louder.

The problem usually is that you need to mount the CB set itself somewhere conveniently reached or out of the way, often under the dashboard, and having the internal speaker pointing down at your feet, you might not be able to hear it too well. Or you have a noisy old bus like a land Rover with a lot of back ground clatter, and wont hear the set over the top.

An external speaker, lets you site the sound more conveniently for where you want to hear it, and gives the chance for some amplification, if it is a bit quiet or has a lot to compete with.

Basically though, a lot of the more sophisticated functions are not all that essential. If you are out green laning in a group, you'll all agree a channel to talk to each other on before you set off. So all you do is set that channel, transmit once to make sure every-one can hear you. Listen to them do the same, and set your squelch, and that's all you need.

Set Location

What is worth thinking about though, is where in the car you are going to mount the set, whether it will have to go under the dash, or under a seat even.

Shown here's my rig as mounted in Jaqui's dash. This is a convenient spot, and as mentioned, it fits conveniently into a heater vent, which I can live without.

The display is clearly visible, and the controls and mic easily reached from the driving seat, but aren't in the way.

And in Jaquis relatively quiet cab, the internal speaker is loud enough, and not obscured enough to need an external speaker; though I do have ideas about using a CD walkman connector to feed it into the radio

When I had the rig in Wheezil, placement needed a bit more careful consideration, as the dash in a series is fairly skimpy and cluttered, and the cabin pretty loud.

Solution there was to make up a roof console in MDF, to sit above the rear view mirror, which took a standard cassette radio, and had the CB hung underneath.

Conveniently the internal speaker is on the under side, so it was pointing sound down to where it was wanted, and could be heard quite well over the clatter of cabin noise, of which there was a fair bit, despite the sound proofing, again, saving the need for an external or amplified speaker.

However, while these worked for me, there's no guarantee they'll be useful for you.

Possibilities of mounting position, are almost endless, and there's probably a lot of personal preference in there, some people might like them tucked out of sight, others where they are most accessible

Thing is, to look where you could fit the set, and work out what features the possible positions you'd want or might have to use would need.

I mean, if you would have to put the set behind or under the drivers seat, then an external amplified speaker and a microphone with set function buttons is going to be useful if not essential.

And size of the unit, too, most CB sets are actually a bit smaller than a standard car radio, but they are often deeper, and where the aerial socket is on the back, they will need a bit of extra clearance for the connections.

And the connections, too might have influence over where you can or can most readily mount the set. You will need power cables and the aerial lead, fed into the back of the set, and these have to be routed somewhere, and again, where they will be routed from, what they will have to be passed through, holes that might need to be drilled, and things like that, could do with though before hand.

Aerials

So onto aerials. Essentially its just a stick of wire poking up into the air, but there are so many types. Some are made of glass fibre and have a thin wire inside them or wrapped around the outside. Some are made of specially conductive rubber. Some are just ordinary metal.

The thing is, that the aerial needs to be as long as possible for best range and reception, and mounted as high as possible, with as little obstruction around it as possible.

With a 4x4, the main problem is that the vehicle is already tall, and a squeeze to get through height restrictions for car-parks and the like, and if you go green laning you could easily be driving through low trees, and the aerial is going to be vulnerable.

The most popular type for 4x4 use, has, through experiment and a lot of lost or broken aerials, has proved to be a three foot solid 'springer' aerial. That is, its all metal, about 30-40 inches long with a big spring at the bottom.

Some people use slightly shorter rubber aerials, and accept the limitation of range and reception, and some people use longer aerials and accept that they might break them. But the 80cm 'springer' has proved to be a rugged reliable type that is a good compromise, and is a pretty good starting point.

And the advice given, is buy as good as you can get, don't be tempted to get a 'budget' or unbranded aerial, as, in comparison to the price of the radio set, they are not expensive, and have more influence over the quality of reception and transmission than anything else. Cheap aerials start at about 5 and go up to about 30. Don't worry too much about power rating though. Some aerials are rated at anything up to 2Kw transmission power, but unless you want to set up a pirate radio station, this probably isn't particularly relevant, and power rating isn't much of an indication of quality.

But how to mount it? Popular choice is with a magnetic mount. This sticks to the roof with a big magnet, and doesn't require any drilling or anything, and of course can be easily removed. Not much good on a Land Rover though, with an aluminium body, as magnets don't stick to it, but in other vehicles with a steel roof, quite useful.

Personally, I have seen people struggling with these going under trees, as the magnetic base hasn't been as strong as the aerial spring, and they have been knocked off. I'm told that if you have a magnetic mount that is big enough, with an appropriately sized aerial, this doesn't happen though. Better in my opinion, are gutter mounts or hatch back mounts.

These clamp to the gutter rim around the roof, or to the lip of a door frame, and in my opinion, are a bit more secure. Certainly I've not seen any one dislodge a gutter clamp, but you do need a gutter to fit them, and few modern cars have them any more.

I have heard a few comments about hatch back mounts though, they can scratch the paint work if clumsily fitted, and on some vehicles they can work loose. But they are possibly more reliable than a mag-mount, and don't need you to drill the body of the vehicle to fit.

But keep an eye on the cable where it goes through the door seal, because they can fret with lots of opening & closing, which can damage either seal or cable.

Last type, is probably the most secure, and that's a stud mount. This fits through a hole in the body, or anywhere else you can drill a hole, for that matter, like a roof rack rail, or a bracket on the back of the car.

On a Land Rover, one useful point to mount one is the rear work lamp bracket, just above the rear door.

When looking for a place to mount your aerial, the ideal place is considered to be the centre of the roof. It's as high as it gets and there's nothing around to block the signal. But its not always that practical.

Mounting on the wings is often considered, but you loose height with a wing mounting, and also the cab of the vehicle will mask a lot of the signal, so mounting on the edge of the roof, is probably the next best choice, and you'll see many 4x4's with their aerial on the edge or back, mounted near the roof line.

For Jaqui, I made up the hinged bracket and stud mount, shown in the pic screwed to the rear A-pillar.

Made from two right angle pieces of aluminium, the 'hinge' is clamped in friction with rubber washers to keep it upright, but still allow it to be bent over double, either deliberately, or if the twig gets snagged on something

When it was fitted to Wheezil, I always cringed going into car parks under height restrictions. One day, coming out, the exit barrier was lower than the entrance, and it pulled the aerial off as I went under!

After that, I kept the aerial dismounted, unless I was laning; but I was always worried that the kids would play with the rig, and without the aerial, blow my transmitter transistors.

Jaqui's hinged mount is not the most ideal for reception or transmission, BUT practically, works well, and the aerial can stay attached permanently; folded down out of harms way when needed.

 

SWR - Standing Wave Ratio

Last thing about the aerials is the 'SWR' or Standing Wave Ratio. When you transmit through an aerial, a certain amount of the transmitted signal is reflected back down the aerial into the set.

If you have an aerial that is the wrong length or damaged, or no aerial at all, it is possible to burn out all of the transistors in your radio set. So you need to make sure that the SWR is within limits.

To check this, you get a little device that goes between the aerial and the radio, called an SWR meter, and it will give a reading from 1 upwards. Anything over 3 is dangerous, 2 is about OK, 1.5 probably about the best you'll get, and 1 is ideal.

A lot of modern aerials are sold 'Pre SWR'd and by accounts, they seem pretty good, but as the dealers are a bit particular on warranty on the radio transistors from people blowing them trying to improve performance messing around with aerials, best to get an SWR meter and test it yourself to be sure.

They aren't expensive, at about 10, and you can have hours of fun adjusting the length of your aerial with a little grub screw, trying to get that perfect 1:1 SWR.

And that, is pretty much it, but I have found an old 'clipping' article, and recently added it to the site for reference, so you may like to see; "Two-way traffic! - Magazine Clipping Article; How to Install a CB 'rig' " over in the workshop.

Conclusion

Other 'Stuff'

Some Useful CB Channel 'allocations'

UK 40 Channels

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