Amateur radio is a unique activity which puts hundreds of thousands of people all over the world into direct contact with each other every day.
There several million licensed amateur radio enthusiasts in the world in virtually every country who are free to operate their radio stations from their homes or their cars or even on board ships. In some countries it is also possible to operate from aircraft. National, political and ethnic barriers are non-existent, thus promoting international friendship and understanding. Amateur radio surely represents a priceless freedom which must be measured.
Because of the potency of radio, amateur radio, like all other radio services, has to be controlled on an international basis. The controlling body is the International Telecommunications Union (ITU) based in Geneva which is an agency of the United Nations.
This body allocates strictly defined bands of frequencies on which amateurs may operate, in the same way in which it allocates frequencies for radio and TV broadcasting stations, aircraft communications, emergency services, military and many other users of the crowded radio spectrum.
The ITU recognises the importance of amateur radio in it's definition of the service - 'A service of self training in radio communication which encourages international friendship'. Because relatively simple low powered equipment n skilled hands is capable of communicating all over the world, this potency must be matched by a responsible attitude by those using this marvellous facility. The amateur radio fraternity is represented at the ITU by the International Amateur Radio Union (IARU). Each country has it's own organisation, in our case the Radio Society of Great Britain (RSGB), which is represented at the IARU. Some other noted members are the American Radio Relay League (ARRL), DARC of Germany, URE of Spain. All countries wisely demand that it's radio amateurs pass an examination before they can receive a licence to transmit. In Great Britain, the issuing body is the Radio Agency (RA) which is part of the Department of Trade and Industry (DTI). At present the examinations are set by the City and Guilds. A reasonable level on technical knowledge is required to design, build equipment and operate to a high standard giving a minimum risk of interference to other services. It is this technical training that differentiates amateurs from almost every other user of the radio services including members of the general public in those countries which allow citizen band (CB) operation. This may sound a little forbidding, but a learning and examination structure allowing amateurs to start simply and get more privileges as they get more knowledge, is in place. One of the attractions of this hobby is that no-one is excluded and all kinds of people from Kings to school children, from US senators to spacemen, from celebrities to shop assistants can be found on the bands. Despite more than 100 years of radio history, the field is still wide open for these people to make genuine contributions to the radio art. This is rather remarkable in these over inhibiting days of red tape and bureaucracy.
There are many modes by which amateurs communicate. Speech, using amplitude modulation, frequency modulation or single sideband, is the most popular mode. Even so, many operators still use morse code or one of the more modern computer generated modes such as PSK31, while some older computer generated modes like RTTY, AMTOR and PACTOR are still widely used. Two types of television are in use. Slow scan television is used on the short wave bands to send single images (similar to a fax) worldwide. Fast scan television, such as you see on your normal TV, is mostly used on the UHF bands
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Radio waves, like light waves, travel in straight lines and cannot pass through obstructions. From a practical point of view, the earth's curvature represents a very significant obstruction. Over a distance of 500 miles, a short distance in terms of communication, this curvature is equivalent to an impenetrable obstruction greater in height than Everest. Fortunately there are various ways, depending on frequency, in which signals can avoid this and other obstructions.
We all know that on our domestic stereo system or personal transistor radio that there are different wavelengths shown. There usually is the long and medium wavebands plus the FM waveband. On the long wave we have BBC Radio 4 and a few other French stations. On the medium wave we find many UK stations most of which are local broadcast stations. The FM band is to be found in the Very High Frequency (VHF) part of the spectrum. The amateur wavelengths are on the shortwave bands, the VHF bands, the Ultra High Frequency (UHF) bands and the Super (SHF) and Extra High Frequency (EHF) bands. In round figures, the amateur bands are 160 metres, 80 metres, 40 metres, 30 metres, 20 metres, 17 metres, 15 metres, 12 metres, 10 metres in the short waveband, while 6 metres, 4 metres and 2 metres are in the VHF waveband with 70 centimetres and 23 centimetres are in the UHF waveband. There are other amateur bands in the SHF and EHF wavebands.
Radio waves shorter than 10 metres are not usually refracted back to earth and so you cannot make long distance contacts by means of your signal hopping around the world between the ionosphere and the earth's surface. At these much shorter wavelengths, say of 2 metres and below, amateurs have to look for an alternative to the natural ionosphere in order to transmit their signals over longer distances.
Under certain weather conditions, usually associated with high pressure, layers form in the lower atmosphere at heights up to 5Km, but normally around 1 to 2KM, which are associated with abrupt changes in air temperature. The boundary between warm and cold air can also reflect radio waves. When these unusual conditions occur, interference to your local FM radio stations or TV pictures from afar can often be noticed. Amateurs take advantage of such conditions to make contacts at long distances.
Everyone is familiar with the 'Northern Lights'. Particles radiated from the Sun are trapped in the magnetic field of the earth becoming densest at the poles. This gives visual effects of shimmering colours in the sky. Ionisation of a lower part of the ionosphere occurs also concentrated at the poles which forms an erratic mirror for VHF signals enabling contacts up to 2000Km.
Thousands of meteors burn up in the central region of the ionosphere every day. The high temperature causes ionisation for periods of time from a few hundredths of a second up to 20 seconds depending on size of the meteor. By using high speed morse code or digital transmissions contacts can be made from between 700Km and 2000Km.
There are other ways on the VHF bands to achieve longer distances such as Trans-equatorial propagation (TEP), Sporadic E, Auroral E, Field Aligned Irregularity (FAI), Ionoscatter and Troposcatter to name a few. With the exception of TEP, the propagation is enhanced in the middle region of the ionosphere.
Many amateurs use the moon as a mirror to reflect VHF and UHF signals to the other side of the world. The path from earth to moon and back is very lossy to radio signals and only the best equipped stations are able to use this method. A much easier possibility of space communication is to contact the International Space Station (ISS). Almost all astronauts on the ISS are licensed amateurs and have equipment installed for their leisure time. Similarly, the Space Shuttle has licensed astronauts making the trip from time to time. This is not a new facility as the Russian MIR cosmonauts were mostly licensed amateurs making many thousands of contacts on many different modes.
Amateurs often have radio installations in their car but of course the distance of normal car to car communication is necessarily small. To overcome this problem amateurs have built and installed hilltop receiver-transmitters, which they call repeaters, which retransmit speech from cars to give these mobile operators extended range. A new facility links many of these repeaters world wide via the Internet which means mobile operators may contact stations world wide with just a low power car installation. Another form of repeater is the amateur satellite. Amateurs have launched to date a little more than sixty satellites for amateur communication. These can relay most types of communication such as speech, digital and television over long distances.
Designing and building is a vital part of the hobby. For some amateurs it is the most important bit while the operating is just the proof that it works. Home building is often the only way to get equipment working at a sufficiently high standard to utilise our bands in the best and most efficient way. The link between transmitter and the outside world is the aerial (antenna). For most amateurs their aerials are limited by the size of their garden and as such it always necessary to optimise a home built antenna to work in the best way.
One way to compare one's station with other amateurs is to take part in contests. The object of a contest is to contact as many stations as possible in a period of time on a certain band or on certain bands. Operating skill and a well setup station plus a good knowledge of propagation is necessary.
Many amateurs enjoy obtaining various awards. The most noted award is the DXCC (DX Century Club). DX can be interpreted as Long distance or a rare station. The requirement for this award is to submit proof of contact with 100 different countries. Proof is normally accepted to be qsl cards from 100 countries. Qsl cards are postcard size cards which the station which you contact sends to you containing details of the contact to confirm that two way contact in fact happened. These cards are normally sent via a qsl bureau. These are usually run by the national society in each country who forward the cards to the other countries.
Most countries have an amateur emergency service setup in case a disaster occurs and the normal communications are damaged or destroyed. In the UK this is RAYNET. Raynet will co-ordinate communications under the control of the local county council emergency committee. The last major operation in the UK was the Lockerbie disaster where the police and county council communications were totally overloaded and due to the very hilly nature of the terrain, many areas were out of reach of the professional services.
Raynet will also respond to pass on messages when there is a major disaster in a foreign country where UK nationals may be present or where nationals of that country living in UK may wish to contact their relatives at home. Abroad, major disasters where communication systems are more sparse than here in UK, occur quite often. In recent times Earthquakes in Alaska, Mud slides and flooding in Central and South America have given the amateur emergency services plenty of work.
Professional engineers mostly work in a very narrow field in the radio/television business and as such do not have such a wide knowledge as the average amateur. Also the normal professional engineer will have no operating skills and propagation knowledge. A professional radio circuit will of necessity be of high quality 100% reliability unlike an amateur circuit which can be a very marginal one utilised very expertly by the amateur.
Often amateur operating modes and techniques are too sophisticated for the average professional.
Amateur radio is a marvellous hobby for the housebound, the blind and persons with other handicaps providing them with a link to the outside world.
It is hoped that these notes will provide a guide to the special magic of amateur radio - an activity that anyone can take up.
Radio Society of Great Britain (RSGB) 0870 904 7373 http://www.rsgb.org