C.B.Radio *************************************************************************** 1. About C.B. Radio 2. UK C.B. 27 Megs 3. UK C.B. 934 megs 4. US C.B. Main blocks 5. Antenna 6. Power supplies 7. Other accessories *************************************************************************** 1. About C.B. Radio Citizans band radio first started in the United states of America in 1948 the mode of transmission used was, and still is AM or Amplitude Modulation. There is another mode called SSB (Single Side Band) it sounds rather like Donald Duck, and with SSB the transmission of the radio waves is far greater. At the reciever end there is a B.F.O or Beat Frequency Occilator which decodes the SSB signal to give a full inteligable output through the speaker. There are more than the 80 American channels that are here in this program some American rigs have 120 channels or even more, but later in '4' there is the 80 most common channels that are normally used here in the UK. Look at 'IFF 1' you see a typical US 120 channel rig. Here in the UK the mode of transmission used is FM or Frequency Modulation the reason for this is mainly because FM has very little iterferance on Television sets and Radios, although if the antenna is not correctly set on a S.W.R meter then all sorts of bad iterferance can come into effect. To be set up in the correct maner you need a C.B. radio FM 40 channel, a 13.8 volt power supply a S.W.R. metre to set the antenna up correctly, with bearing in mind the antenna must be of an approved type. Back in 1981 when I fist started out in the C.B. world I first started out with a 23 channel American rig then on to a 40 channel Super Tiger AM rig quite ilegal of course with a 18' dipole stuck upon the roof. Those were the days when the knock on the door meant throwing the rig over the back of the settee incase it was the neighbour from next door. But to stay legal in this country you must first have a C.B. radio licence from the post office otherwise the fine for not having one can be upto £400.00, even if you have a licence you may not have the antenna set up in the corrct fashion and be causing all sorts of interferance. If this is the case then you may well recieve a little visit from the DTI (Department of Trade and Industry).Some of the things that are illegal are for example excedding the maximum limit of 4 watts RF output power, not having the antenna S.W.R'd in correctly, faulty Mic, a mind blowing echo chamber, to mention but a few, so be AWARE of what you are doing if you should ever set a C.B. radio up. Should you decide to have yourself a C.B. radio then always look out for a white circle with 27/81 inside it, if there is no circle with 27/81 then be carefull because it is very hard indeed to scrath this emblem of so it may well be ILLEGAL, and check the registration plate somewhere on the back of the rig. Remember using anything other than a UK spec C.B. radio is ILLEGAL. ****************************************************************************** 2. UK C.B. 27 megs Here is a table of the frequencies for the United Kingdom. The channels here have a spacing of 10 khz. CHANNEL FREQUENCY CHANNEL FREQUENCY 1 27.60125 21 27.80125 2 27.61125 22 27.81125 3 27.62125 23 27.82125 4 27.63125 24 27.83125 5 27.64125 25 27.84125 6 27.65125 26 27.85125 7 27.66125 27 27.86125 8 27.67125 28 27.87125 9 Emergency 27.68125 29 27.88125 10 27.69125 30 27.89125 11 27.70125 31 27.90125 12 27.71125 32 27.91125 13 27.72125 33 27.92125 14 Calling 27.73125 34 27.93125 15 27.74125 35 27.94125 16 27.75125 36 27.95125 17 27.76125 37 27.96125 18 27.77125 38 27.97125 19 Truckers 27.78125 39 27.98125 20 27.79125 40 27.99125 Channel 14 where I come from is the Breaking channel it may or may not be the breaking channel where you live. This block has been used for the past 13 years, and there was a time when 40 channels was hardly enough. ****************************************************************************** 3. UK C.B. 935 megs Here is a table of the frequencies for the United Kingdom. The channels here have a spacing of 50 Khz. The 934 block here has only 20 channels. And the maximum effective radiated output power is 8 watts for this band. If an external antenna is used then The antenna can have a maximum of four elements and must not exceed 170 mm in length. This gives a maximum effected radiated output power of 25 watts. CHANNEL FREQUENCY CHANNEL FREQUENCY 1 934.025 11 934.525 2 934.075 12 934.575 3 934.125 13 934.625 4 934.175 14 934.675 5 934.225 15 934.725 6 934.275 16 934.775 7 934.325 17 934.825 8 934.375 18 934.875 9 934.425 19 934.925 10 934.475 20 934.975 ***************************************************************************** 4. US C.B. Main blocks This block of 40 channels are the most widely used here in the UK. Block 1, You may notice that the channel spacing is at times iregular this is to do with the FCC (Federal Communications Commission) of America. CHANNEL FREQUENCY CHANNEL FREQUENCY 1 26.965 21 27.215 2 26.975 22 27.225 3 26.985 23 27.255 4 27.005 24 27.235 5 27.015 25 27.245 6 27.025 26 27.265 7 27.035 27 27.275 8 27.055 28 27.285 9 Emergency 27.065 29 27.295 10 27.075 30 27.305 11 27.085 31 27.315 12 27.105 32 27.325 13 27.115 33 27.335 14 Calling 27.125 34 27.345 15 27.135 35 27.355 16 27.155 36 27.365 17 27.165 37 27.375 18 27.175 38 27.385 19 Truckers 27.185 39 27.395 20 27.205 40 27.405 ------------------------------------------------------------------------------- Block 2 41 27.415 61 27.665 42 27.425 62 27.675 43 27.435 63 27.705 44 27.455 64 27.685 45 27.465 65 27.695 46 27.475 66 27.715 47 27.485 67 27.725 48 27.505 68 27.735 49 27.515 69 27.745 50 27.525 70 27.755 51 27.535 71 27.765 52 27.555 72 27.775 53 27.565 73 27.785 54 27.575 74 27.785 55 27.585 75 27.805 56 27.605 76 27.815 57 27.615 77 27.825 58 27.625 78 27.835 59 27.635 79 27.845 60 27.655 80 27.855 ****************************************************************************** 5. Antennas CB radios must have the antenna set up correctly because if not then you will encounter all sorts of problems, like interferance with TV and stereo this is a common problem. There are may types of antenna you cab buy, the old DV27, or DX27, or a Firestick, Thunderpole MK3 and so on. It might be a bit difficalt these days to obtain this sort of antenna, it might be a good idea to find the breaking channel for your area and ask if there are any for sale, most likely you will soon find one that you can inspect and buy. But the firestick although very good was a bit of a nightmare if stuck to the side of a house, I myself used to have a 18' dipole, witch suited my setup very well indeed. I also used the bottom half of a dipole and for the top I used a DV27, the SWR from this was always inder 1.5 on the SWR metre. Bearing in mind that the antenna you use MUST be LEGAL and no more than 7 metres from the ground. Legal in the fact that the radiating element must not be any longer than 1.5 metres ****************************************************************************** 6. Power Supplies Power suplies that you might well use for the C.B. radio are on average 13.8 v rated at 2 amps but can be in the range of 13.8 v 2/3 amp with 5/7 amp surge. The surge means extra amps from the transformer/circuit, if you look at the IFF's PSU 1 to 3 you will see some power supplies for a C.B. radio. The surge is used normally on transmitt when the 4 watts go out through the arial, however extra amps from the transformer/circuit are not normaly called for unless you are using an ILLEGAL burner or if you have the C.B. radio tweeked up, that means the coil windings have been tampered with to extract more R.F. power. This is not a good idea as the more R.F. power used, that is more than the permitted 4 watts, then the more chance of inteferance you may cause to other domestic appliances. Power supplies cost from about £19.99 to about £40.00 and can be purchased from places like 'Tandy', 'Maplin Electronics' and other good places. If you decide to make a Power supply yourself then make sure you know EXACTLY what you are doing, dealing with the mains can be very HAZARDOS. ****************************************************************************** 7. Other Accecories There are quite a few of these you can get, such as a Power Mic, an Echo Chamber, SWR Metre, Backup Power Supply, Mic extension lead, a combined RF metre-SWR metre. Power mic's are alright I suppose but if the conditions are correct and you only want to work localy then it would be of little use really, but more of use if you want to DX that is to transmit as far as possible then if the Power mic is set correctly then you will find that people at a great distance will hear you more clearly. An Echo Chamber these vary in quality, but basicaly these gadgets give you control over your voice being transmitted I used to have one myself and if set properly then the effect can be very good, but this is not actually a needed item. In fact many people have the reverb up too far and the effect is very anoying, and often distorted. A good SWR metre is a very good idea to have in-line with your CB radio between the antenna socket from the CB end and the antenna itself. this way if anything should happen to the antenna you are using then you will see the differance straight away. To use an SWR metre, by the way SWR stand for Standing Wave Ratio, the idea is to give you information reading from the metre scale to tell you if the antenna is set corectly or not. This may take sometime if you are doing it yourself, it would be a better idea to have someone who knows about the SWR metre give you a hand. Right to use an SWR metre first you should see a switch on the front panel that says FWD (Forward) and REF (Reflect) put this in the FWD position, then go to channel 1 but make sure no one is using it first if so then try channel 2, when you have done this then key the mic you will see that the metre on the CB has gone from left to right indicating power output and the metre on the SWR has also done the same to a degree, well set the variable control on the SWR metre so that the needle reads to the far end of the scale see the IFF 'SWR' for a better description, then release the mic and switch from FWD to REF and then key the mic again with any luck you should see a slight reading the smaller the reading the better. Most people are happy with say a 1.5 ratio. If you have this reading on the REF postition then this will be safe for you CB. A power metre can be a seperate item or sometimes it may be a combined unit the RF power metre will give you a reading concerning the RF output from the CB radio you will see a scale something like 1 to 5 watts or even a double scale 1 to 5 and under that a 5 to 10 watts, well if the SWR metre is reading correct then so should the RF.WATT metre. So the ideal reading should read 1,5 SWR and 4 Watts output. see the IFF 'RF.SWR' metre for more detail. It is always a good idea to have a backup Power Supply or if not then there is no harm at all in using a 12v car battery, in fact I used to have a 12v car battery as backup anyway. Also you can have a extension lead for the mic because some people like to relax back in the chair and there are times when the mic lead is not long enough. ******************************************************************************