- Created on Wednesday, 01 July 2009 08:45
- Last Updated on Monday, 01 April 2013 14:46
- Written by Khalid Shoaib AP2MKS
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AMATEUR RADIO IS RESPONSIBLE
For putting hundreds of thousands of people all over the world, into direct contact with each other every day. Worldwide, there are over one
and a half million licensed amateur radio enthusiasts spread across virtually every country, who are free to operate their radio stations from their homes. National, political and ethnic barriers are non-existent, thus promoting international friendship and understanding.
Amateur radio represents a priceless freedom which must be treasured.
Because of the potency of amateur radio, like all other radio services, it has to be controlled on an international basis. The controlling body is the International
Telecommunications Union based in Geneva, which is an agency of the United Nations Organization. This body allocates strictly defined bands of frequency on which amateurs may operate, in the same way that it allocates frequencies for radio and TV broadcasting stations, aircraft communications, emergency services and scores of other users of the heavily loaded radio spectrum.
The ITU recognizes the importance of amateur radio in its definition of the service - ‘A service of self-training in friendship’. Relatively simple home-constructed equipment, in skilled hands, is capable of communicating all over the world. This potency must be matched by a responsible attitude by those using amateur radio facilities.
All countries wisely demand that radio amateurs pass a technical examination before they can obtain a licence to transmit. This is to insure that they have sufficient technical background to design, build, maintain and operate their equipment to high standards with minimum risk of interference to other radio services. It is this technical training that distinguishes amateurs from almost all other actual users of the radio spectrum. This includes members of the general public in some countries where citizen band radio is in operation. If this sounds a little forbidding, it is surely one of the attractions of amateur radio that it includes in its ranks kings, lords, senators, schoolboys, schoolgirls, and old age pensioners - in fact, people from all backgrounds.
Despite its long history, the field is still wide open for people to make a genuine contribution to the art of radio. The scale of operation by amateurs sometimes comes as a surprise. To date, there have been nearly thirty communication satellites put into orbit, built by amateurs. Several are currently operational.
How Radio Amateurs Communicate
Most amateur operators communicate directly by speaking. It is like a telephone conversation when reception is good. Most amateurs around the world can communicate in English, which therefore tends to be the common language used.
This is a most effective and attractive means of communication, requiring the simplest of equipment. At present, everyone has to demonstrate their ability to send and receive Morse Code before they can obtain a licence to transmit on the short wave (as opposed to the VHF) bands. One advantage of using Morse Code is that it has a number of standardized abbreviations which allow communication even when there is no common language.
Many amateurs can transmit colour television pictures to each other. Normally the range of these transmissions is tens of miles. However, amateurs have pioneered a system called ‘slow scan’ television which enables amateurs with suitable equipment to transmit pictures around the world.
Amateurs can also use their home computers to communicate by ‘typing’ messages to each other across continents.
In most countries no special licence is required to receive all the different types of signals transmitted by radio amateurs around the world.
The Way Amateur Signals Get Transmitted
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 obstacle. Over a distance of 500 miles, which is a short distance in radio terms, this curvature is equivalent to an impenetrable barrier, greater in height than Everest. Fortunately there are various ways, depending on the frequency, in which signals can avoid this and other obstructions.
We all know that on ‘long wave’ the BBC transmits on 1515 metres. Also that radio 5 is on a wavelength of 330 and 433 metres on the ‘medium wave’. The amateur wave lengths (or bands) are on short waves.
These are in round numbers, at 160 metres, 80 metres, 40 metres, 30 metres, 20 metres, 17 metres, 15 metres, 12 metres and 10 metres. There are also amateur bands at wave lengths of 2 metres, 70cm and 23cm; smaller than this would be identified as ‘microwaves’.
Centred at about 250km (150 miles) above the earth’s surface there are layers of ionised gas called the ‘ionosphere’ encircling the earth. Under certain conditions, these layers can act as fairly efficient reflectors of ‘short wave’ signals. Radio signals bouncing off these layers can be reflected back from the earth’s surface back into the sky to be reflected back again and so on. A series of hops can carry signals around the world. If a radio signal continued, it would go seven times around the world every second.
SHORTER THAN SHORT
Radio waves shorter than 10 metres are not normally reflected back to earth and so you can’t 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 wave lengths, say of 2 metres and below, amateurs have to look for an alternative to the natural ionosphere in order to reflect their signals over long distances. Other natural conditions can help such as:
Under certain weather conditions, usually associated with high atmospheric pressure (a ‘high’), layer form in the lower atmosphere at heights of 1 to 2km (about 1 mile) which are associated with abrupt changes in air temperature. The boundary between the hot and cold air can also reflect radio waves. When these ‘freak’ radio conditions are present (often referred to as ‘freak atmospherics’) interference to your television conditions can occur from distant stations. However, amateurs take advantages of these ‘good’ conditions
to make contacts with stations of typically 1,000-2,000km (over 1,000 miles) distance.
International contacts are possible using the same principle of an elevated site; in this case a communication satellite orbiting the earth. Amateurs take an active part in designing and building satellites
Everyone has heard of the ‘Northern lights’. Particles radiated from the sun under special conditions become trapped in the earth’s magnetic field and give off light. Sometimes when this happens parts of the atmosphere become ionised. The ionisation may be so strong that very short wavelength radio signals can bounce off these ‘Northern lights’. Amateurs also use this natural phenomenon to make contacts over hundreds of kilometres.
Hundreds of meteors burn up in the outer layer of the earth’s atmosphere every day. The high temperature of the burning meteor can cause very high ionisation for a few seconds. By using high speed Morse code transmission techniques, radio amateurs can exchange information in these few seconds and make a worthwhile radio contact. In difficult conditions amateurs thrive, whereas professional communicators, because of poor reliability, would not accept these methods.
The moon is of specific significance to the hundreds of radio amateurs enthusiasts around the world, who use it as a reflector, to bounce signals from continent to continent. This method of communication is marginal and demands very high standards in the design and operation of amateur equipment.
When amateurs run out of natural things to bounce their signals off they make unmanned relay stations. In the UK, there are some three hundred voice relay stations and a similar number of data relay stations, which receive transmissions from radio amateurs and re-radiate them from elevated sites. The voice repeaters are primarily used to assist amateurs to communicate
from car to car and to extend the range from a few kilometers to tens of kilometers.
MANY AMATEURS ENJOY WORKING TOWARDS various operating awards. These
are given in return for proof of having made contacts with various amateurs around the world. The ‘proof’ is in the form of ‘QSL’ cards - which are highly professional postcards which amateurs like to exchange to confirm their radio contacts with each other. An elaborate system has been developed to circulate the millions of cards generated each year and the Radio Society of Great Britain is one Society of many, which operates its own bureau for processing these cards.
In contrast to most professionals in radio communications, who generally are specialists in restricted aspects of the subject, many amateurs have a uniquely broad experience covering all aspects of communication. The experience is invaluable in enabling them to set p, from scratch, radio communicating systems have broken down. During many man-made and natural
disasters, the only form of communication with the outside world for the first critical ten hours has often been an amateur radio station set up using the special skills of these operators.
Amateur Radio is obviously of special values to the blind and immobile. For them it provides a unique link to the outside world.
Amateurs have a significant role to play in the development of the art of radio communication. They complement, rather than compete, with their professional brothers. Amateurs are not required to provide a reliable propagation method which can be of little value to professionals.
Courtesy : AP2AUM