HISTORY
In September 1895, Guglielmo Marconi, a self-taught 21-year-old from
Guglielmo Marconi – father of Ham Radio
Guglielmo Marconi was born at
In 1896 Marconi took his apparatus to
In 1900 he took out his famous patent No. 7777 for "tuned or syntonic telegraphy" and, on an historic day in December 1901, determined to prove that wireless waves were not affected by the curvature of the Earth, he used his system for transmitting the first wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2100 miles.
Between 1902 and 1912 he patented several new inventions. In 1902, during a voyage in the American liner "
Marconi died in
INTRODUCTION
Ham radio is a scientific hobby of wireless communication between citizens by means of private two-way radio for personal communications but not for third party traffic, or business. It is defined by international convention as "a service of self-training, intercommunications and technical investigations by duly authorized persons interested in radio technology solely with a personal aim and without pecuniary interest". But actually it is far more than that.
That is to say, it is the hobby of two-way radio communication (as distinct from broadcast or commercial traffic) mainly with a view to encourage experimentation and intercommunication with other amateurs on a personal basis. While many amateurs treat it as a hobby for enjoyment only, behind every amateur lurks the desire for inventiveness, ingenuity and public service.
However, Pat Hawker G3VA has a more interesting definition: "The practice of two way, shortwave radio communication not as a business or means of profit, but a spare time hobby pursued for the pleasure derived from an interest in radio technique, construction and operation and for the ensuing friendship with like minded individuals throughout the world".
For the constructor, it is an endless pursuit of making new gadgets and devices and tinkering with his equipment. May hams start by building their first receiver - from bits and pieces. Their reward is the indescribable thrill of receiving sounds from hundreds of miles away. In the process they learn a lot.
For the compulsive talker it is endless "ragchew". For the public spirited citizen it is receiving messages as a public service. He may provide badly needed communications in times of natural disasters.
For the experimenter it is innovation and adaptation and will lead to new inventions in technology.
For the handicapped it provides a link with the world and sometimes the only way to maintain sanity and not die of boredom.
There are also the awards hunters, "DX"-men, contest fans so on. To the hobbyist it is a time of relaxation, chatting with friends all over the world, most of whom he has never met, but still known them intimately by talking to them often. For the Boy Scout it will provide his "good deed". To "the ordinary man" away to kill time by talking to his friends until the wife announces that dinner is ready and the big switch must be pulled at once! In short there is-something in amateur radio for everyone. In all cases it is a powerful influence for building international goodwill. It has attracted Kings, statesmen, prime ministers, engineers, clerks, industrialists’ peons, businessmen, teachers, and shopkeepers - almost everyone.
Fun for all ages
The public service record of the amateur is a brilliant tribute to his work. In hundreds of emergencies, natural disasters such as storms, floods, earthquakes, civil commotion, forest fires, accidents or for expeditions, motor rallies and so on, amateurs have provided badly needed communications where everything else failed. There are famous examples such as the Agadir and the
What Ham Radio is not:
(a) Citizen's Band: This consists of some spot frequencies in the 27 MHz. bands for personal or low powered equipment. Licenses are given without a test, but hesitatingly! The use of CB has grown to such proportions in the
(b) Experimental Licenses, are given for experiments where radio waves are involved.
This is the only hobby governed by International Convention. The World Administrative Radio Conference (WARC) meets every few years in
A note-worthy requirement to be always remembered states:
"Communications should be of such unimportance that you would not normally resort to Government telecommunications".
The electronics industry in the
The Times of India, in a editorial some years ago, had this to say: "The amazing growth of electronics in
The editorial went on to comment on the unhealthy constriction of amateur talent in
Wayne Green, Editor of "73" Magazine, puts across this idea very well:
"We are today keeping up pretty well with our missiles and technology. But all of us recognize fully that electronics is a fast-growing field and that as it expands we will have to have perhaps ten times as many engineers and technicians as we have today, in just a few years.
You don't start being an engineer in middle age; you start in your teens. And you don't start being an engineer in your teens if you are spending your time protesting, roving with a street gang. or dropping out. The reason we are able to have the number of engineers and technicians that we do today is very largely due to the influence of amateur radio on two or three hundred thousand teen-agers in the last 50 years. Well over 80 per cent of the high school hams go on to work in electronics and communications. What do you think would happen to our electronics industry if every man who got started via ham radio were to drop out?"
HAMS – in
Today, there are approximately 675,000 amateur radio operators in the
Amateur radio operators are often called ham radio operators or simply "hams." (The origin of this nickname is for all practical purposes lost. Although some people still speculate about, few agree and even few care. Amateur radio operators proudly call themselves hams and nobody knows why.)
The Amateur Radio service is governed by the Federal Communications Commission, which sets the rules for the service in the
To become an operator and use these frequencies, international agreements between nations have required perspective hams to pass an exam. Here in the
The amateur radio fraternity comprises hundreds of thousands of people worldwide who share a very broad common interest. Amateur radio operators come from very diverse backgrounds and age groups. Ranging from adolescents to senior citizens, boys and girls, men and women - amateur radio operators include doctors, bus drivers, vetinary surgeons, painters, engineers, homemakers, university professors, students, politicians, laborers, lawyers and the retired as well as the unemployed, there are no limits to backgrounds.
LICENSE REQUIREMENTS – in
You need an easy-to-earn license to transmit on an amateur radio frequency. License tests cover electronics theory and amateur radio rules and regulations. Study guides are readily available. There is no age restriction. Each country has its own licensing arrangements. Many countries share many of the same frequency bands with hams in the
Recently, the FCC relaxed the Morse code requirements portion of the rules to make it easier to get an amateur radio operator's license. The FCC's new licensing plan means you will be able to become a ham by passing a single 35-question written examination. License study guides are readily available for the written test.
The American Radio Relay League (ARRL) helps many get into amateur radio. The ARRL was organized in 1914 by H.P. Maxim to help relay radio messages. Most radio messages had a 25-mile range at that time and were transmitted around 1.5 MHz, at the high end of the AM broadcast band. The ARRL has many useful publications. Local volunteers around the country administer amateur radio tests. These volunteers are usually members of an amateur radio club.
The FCC licensing requirements includes a mixture of written tests for several license classes and a Morse code test of five words per minute for some license classes.
The written tests consist of multiple choice exams. You can access online study guides or you can buy them. Each type of license has specific operating privileges on each ham band
To transmit on the publicly owned amateur radio airwaves, you need an FCC Amateur Radio License. The license is relatively easy to acquire. All you need to do is pass the Technician Class licensing exam at a local Volunteer Examination Site.
What is ARRL and FCC?
Full members of the ARRL control the Organization through an elected Board of Directors, Volunteers (all positions except for HQ staff) accomplish much of the work.
Hams in other countries have formed national organizations, just as US hams organized the ARRL—the national association for Amateur Radio. These sister societies work together to have a united voice in international radio affairs, such as when governments get together to decide how radio frequencies will be divided among its various users. The International Amateur Radio Union (IARU) composed of about 150 national Amateur Radio societies, works to advance the cause of Amateur Radio at the international level. ARRL works closely with other IARU societies to help protect the amateur frequencies.
The administrators: ITU and FCC
The laws of physics allow for a limited spectrum of radio frequencies. These radio frequencies must be shared by many competing radio services: broadcasters, land mobile, aeronautical and marine, to name a few.
The International Telecommunication Union (ITU), an agency of the United Nations, allocates these frequencies among the many services that use them. With its long tradition of public service and technological savvy, ham radio enjoys the use of many different frequency bands. In the
The ARRL
Since it was founded, in 1914, the ARRL has grown and evolved along with Amateur Radio. The ARRL Headquarters building and Maxim Memorial Station, W1AW, are in
The ARRL operates as a nonprofit, educational and scientific organization dedicated to the promotion and protection of the many privileges that ham radio operators enjoy today. Of, by and for the radio amateur, ARRL numbers within its ranks the vast majority of active amateurs in
There were no computers, Satellites or TV when Clarice,
W7FTX, was first licensed in 1935. One thing has not Changed—the friendship of her fellow hams.
Around 170,000 licensed ham radio operators and unlicensed persons with an interest in ham radio are members. Licensed hams join as Full Members, while unlicensed persons become Associate Members who have all membership privileges except for voting in ARRL elections. Anyone who has an interest in Amateur Radio has a place in the ARRL. The ARRL volunteer corps is called the Field Organization. Working at the state and local level, these volunteers carry out the work of ARRL to further Amateur Radio. They organize emergency communications in times of disaster and work with agencies such as the Red Cross, the National Weather Service and Civil Air Patrol. Other field volunteers keep state and local government officials abreast of the good that ham volunteers are doing at the state and local level.
HAMS – IN
There is now indication that the importance of hams is being realized in
Amateurs in
But the most outstanding example of public service was in October 1993 during the Latur Earthquake. On this occasion hams of
The communication provided by us during the Morvi dam disaster was a landmark effort.
Here too, the Home Guards and local officials considered our efforts as invaluable.
The Himalayan Rally Association has used our services for ten consecutive years and they acknowledged that it would be impossible to run the rally without our communications setup. Another recent example is the outstanding work done by
Every year two days are set apart for Boy Scouts numerous examples of medical emergencies where and Girl Guides to use amateur radio for exchanging hams greetings with their counterparts all over the world.
LICENSE REQUIREMENTS – in
The rules and regulations required to get the license in
1. You should be an Indian citizen (special rules apply to foreigners)
2. You should be 14 years old (12 years for Grade II)
3. You should have passed the examination in the appropriate Grade including the Morse test. (2m, VHF licenses are given nowadays without the Morse test). The various types of licenses and their privileges are given in the rules. There are several types of radio operator’s certificates which may exempt you from the amateur exam. A grade of license - shortwave listener – is required even for the possession of a communications receiver.
The Question Paper (year 2001) of examination taken by Ministry of Communications, Department of Telecommunications, Government of
The Wireless Planning and Co-ordination Wing (WPC), Department of Telecommunications has the responsibility of coordinating and regulating all wireless activity in
1. Recognition and enhancement of the value of the amateur service to the public as a voluntary non-commercial, communication service, particularly in providing emergency communications.
2. Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art. Historically amateur radio operators have been the greatest contributors to the state of the radio art.
3. Expansion of the existing reservoir within the amateur radio service of trained operators, technicians and electronic experts.
4. Enhancement of international goodwill. It is amazing how amateurs are welcomed by other amateurs. Amateur radio is the best way to make friends all over the world.
The Geneva Convention is adhered to by almost all the countries of the world; otherwise there would be total chaos on the air waves. Amateurs are assigned certain slots in the various frequency bands. In the last WARC conference 1991 amateurs successfully resisted curtailment of their frequencies.
ACTIVITIES
Ham radio operators get in their cars everyday and talk to their buddies all over town. Other radio operators access the "ham radio internet" and send digital messages to their friends through a wireless network using a method called "packet". While still others talk to their friends they've met on the radio around the globe by simply picking up a radio microphone or tapping on their Morse code keys. Hams can even talk to each other live through amateur television, or transmit photos of themselves through special wireless FAX modes. The possibilities are many. It's as simple as that. But ham radio operators also participate in serious activities. They're on a constant alert for emergencies. On a moments notice hundreds of hams can deliver life-saving messages to a disaster affected area.
Ham radio has so many aspects to get involved in that this page would never be able to list all of the things possible to experience. But in a short summary, with ham radio you can experience personal radio communications. With a little radio about the size of a credit card, you can talk to a fellow radio operator in
Ham radio operators use two-way radio stations from their homes, cars, boats and outdoors to make hundreds of friends around town and around the world. They communicate with each other using voice, computers, and Morse code. Some hams bounce their signals off the upper regions of the atmosphere, so they can talk with hams on the other side of the world. Other hams use satellites. Many use hand-held radios that fit in their pockets.
A young operator enjoys making friends over the radio during Kid's Day. Kid's Day is an annual event that encourages young people to get on the air, perhaps with a family member or a neighbor who is a licensed amateur radio operator.
Hams exchange pictures of each other using television. Some also like to work on electronic circuits, building their own radios and antennas. A few pioneers in Amateur Radio have even contributed to advances in technology that we all enjoy today. There are even ham-astronauts who take radios with them on the International Space Station and thrill thousands of hams on earth with a call from space!
Amateur Radio operators do many things. They speak into their radio microphones and their signals leap to the far corners of the world. They communicate by voice, morse code, teletype, RTTY, fast and slow scan television, and through special links between their computers called Packet radio (similar to sending an e-mail on the computer except using a radio).
The Amateur radio service also is a public service. Amateur operators lend their communication's expertise and abilities in times of disasters and emergencies. They can relay messages through their radios over long distances when telephones and power lines are down. Sometimes they are the only way government officials can get messages to disaster ravaged parts of a remote area. Most recent examples of ham operators in action are the Alpine Viejas Fire, the earthquakes in Mexico City, India, El Salvador, Seattle, hurricane disasters in Cuba, Honduras, Florida, and the Sept 11 Attack in New York and Wash. DC. In each case amateur radio operators handled critical emergency traffic out of the affected disaster area when normal communications were knocked out or overloaded.
When deadly floods struck central and southern
FCC (Federal Communication Commission) has set the few following guidelines which govern the usage of Ham Radio by Ham Radio Operators, who are also called Hams:
1. Hams are not allowed to do anything with their radios that makes them money in way. Ham radio is a hobby, but that doesn't mean it's completely frivolous.
2. Ham radio operator cannot `broadcast' to the public. This means that ham radio transmissions are meant to be received by other ham radio operators. While a short-wave radios or scanners will allow you to listen to the ham radio bands, what you will hear is hams talking to other hams and not music or other radio programs of `general' interest.
Within these (and other) guidelines, however, hams are empowered to do just about everything that government and private radio stations are allowed to do.
Using even the simplest of radio setups and antennas, amateurs communicate with each other for fun, during emergencies, and even in contests. They handle messages for police and other public service organizations during all kinds of emergencies including:
Ø Hurricanes
Ø Earthquakes
Ø Tornadoes and floods
Ø Motorist accidents
Ø Fires and chemical spills
Things you can to do with amateur radio:
Ø Talk around the world - With HF (high frequency) radios hams can talk to other hams in literally any part of the globe.
Ø Talk around town - With small portable VHF (very high frequency) and UHF (ultra high frequency) transceivers hams enjoy extremely reliable communications within their local community.
Ø QRP - Communicating with "very low power" is a challenge that many hams enjoy. QRP is usually practiced on the HF bands.
Ø Packet radio - The internet over ham radio? Not really ... but ham radio operators enjoy a digital network of their own, all without wires!
Ø International Morse code - Forget it ... You can get a license without knowing one beep of Morse code. If you want to, though, it's still allowed.
Ø Amateur television - It's just like real television because it is real television.
Ø Slow Scan TV - Send pictures around the world for little or no cost.
Ø Contests - You can put your radio operating skills up against other hams and teams of hams.
Ø Order pizzas - It used to be a long standing joke around ham radio operators about what you can not do over ham radio ... Now it's perfectly legal! You can call you favorite pizzerias on your ham radio and order take-out dinner on the way home from work.
Ø Emergency and other volunteer services - Floods, hurricanes, mudslides, earthquakes, ice storms ... when ever `normal' communications go out, hams are ready to use their radios to provide emergency communication services to their communities.
Ø Satellite communications - Hams have their own satellites ... really! (Amateur's satellites are easy to use too.
Ø Traffic handling - "Ham telegrams" are used to send messages to people around the world at no cost to the sender or the recipient; all done by ham radio operators volunteering their time and resources.
Natural disasters like hurricanes or tornadoes disrupt normal telephone and cell phone systems. Ham radio operators pitch in to help with emergency communications, and you will often hear about them on news reports.
In recent Space Shuttle missions, each member of the crew usually has an amateur radio operator's license. During breaks, astronauts hold their 1- to 5-watt VHF FM hand-held radios up to the shuttle window and chat with other hams for a few minutes, often at schools while the shuttle is in an orbit overhead! VHF transmissions have a limit to line-of-sight communications and normally do not travel over the horizon, so a conversation is limited to the time when the shuttle is overhead. The space station MIR used 145.985 MHz for similar conversations. Future ham radio efforts in space will focus on the use of amateur radio within the International Space Station (ARISS) project.
Rag chewing is the fine art of the long contact. Old friends often get together on the air to catch up on current events. Family members use ham radio to keep in touch. And, of course, new acquaintances get to know each other! In many cases, friends scattered across the country get together to create rag chewing nets. These nets are very informal and may not make much sense to the outsider listening in. The “serious” rag chewer’s shack decoration is not complete without the Rag Chewers’ Club (RCC) certificate.
Emergency Communications
The FCC Rules list emergency communications as one of the purposes of the Amateur Radio Service - and in reality, the ability to provide emergency communications justifies Amateur Radio’s existence. The FCC has recognized Amateur Radio as being among the most reliable means of medium- and long-distance communication in disaster areas.
ARES and RACES
The Amateur Radio Emergency Service (ARES) and the Radio Amateur Civil Emergency Service (RACES) are the umbrella organizations of Amateur Radio emergency communications. The ARES is sponsored by ARRL (although ARRL membership is not required for ARES participation) and handles many different kinds of public-service activities. On the other hand, RACES is administered by the Federal Emergency Management Agency (FEMA) and operates only for civil preparedness and in times of civil emergency. RACES is activated at the request of a state or federal official. Amateurs serious about emergency communication should carry dual RACES/ ARES membership. RACES rules now make it possible for ARES and RACES to use the same frequencies, so that an ARES group also enrolled in RACES can work in either organization as required by the situation.
Military Affiliate Radio Service (MARS)
MARS is administered by the
There are three branches of MARS: Army MARS, Navy/Marine Corps MARS and Air Force MARS.
Each branch has its own requirements for membership, although all three branches require members to hold a valid US Amateur Radio license and to be 18 years of age or older (amateurs from 14 to 18 years of age may join with the signature of a parent or legal guardian).
MARS operation takes place on frequencies adjoining the amateur bands and usually consists of nets. Nets are usually scheduled to handle traffic or to handle administrative tasks. Various MARS branches may also maintain repeaters or packet systems. MARS demonstrated its importance during the 1991 Desert Storm conflict, when MARS members handled thousands of messages between the forces on the front lines and their friends and families at home. While MARS usually handles routine traffic, the organization is set up to handle official and emergency traffic if needed.
CONSTRUCTION
A typical ham radio is a transmitter and a receiver, usually purchased as one unit, called a transceiver. Newer transceiver models often have semi-complicated controls and menu systems that may take some reading of the manual. You may be able to find an older transceiver with controls that are easier to use as a beginner, having the usual analog controls.
Hand-held transceivers have their own antennas. Many hams choose to do most of their operating from their automobile during commute times, using a magnetic mount antenna connected to an under-dash transceiver or a hand-held radio.
AERIALS
The importance of a good aerial cannot be stressed too much. Fortunately it is quite easy to rig up suitable aerials for ham work.
While this is not meant to be a technical treatise, it is essential to give a few details about antenna construction as this is the first step for you in becoming a ham and even for listening as a SWL. Although desirable to cut the aerial according to the frequency to be used.
Frequency of radio waves is measured in Hertz (cycles per second) or Kilohertz kHz = 1000 cycles per second) or Mega-hertz MHz = 1,000,000 cycles per second.
Since electromagnetic waves travel at 300,000,000 meters/second the relationship is:-
Frequency = 300,000,000 (m/sec.)
wavelength (m)
OR
Frequency (kHz) = 300,000
wavelength (m)
OR
Frequency (Mhz) = 300.00000000
wavelength (m)
and:
wavelength in meters = 300,000,000
frequency (cycles/sec)
= 300,000 = 300.00000
frequency (kHz) Frequency (MHz)
A common and useful aerial is the HALF WAVE DIPOLE. If it is to be used for 20 meter band (say 14.2 MHz or 21.12m) then half wave is 10.56 m.
So the aerial thus constructed is:
Actually the arithmetical length of the aerial is 10.56 m, but for certain theoretical reasons it should be 10 m. Three egg insulators are used. The wire between any two is 5 meters (quarter wave). Both wires are connected to a coax cable; the shielding to one section and the core to another. For this type of wire 75 ohm coax is suitable.
For making a dipole for the 40 meters band the half wave length can be calculated accordingly. It will be approximately double this length.
Beam and quad type aerials are more difficult to construct and have unidirectional properties.
There are many varieties of coax cable but those used commonly by amateurs are:
Ø RG11 U or RG59U which has an impedance of 75 ohm (suitable for dipole).
Ø RG8U or RG58U which has an impedance of 50 ohms (suitable for beams).
These are easily available in the market and so are suitable connectors for them. Since amateurs are allotted some frequencies in all the major bands, all of which have different characteristics, you will need different aerials for transmitting on the various bands. There are many excellent books on aerials which can be referred to for details.
A dipole antenna can be installed in three ways:
STRAIGHT DIPOLE: similar to the configuration shown above.
SLOPPING DIPOLE: Where point A is placed higher than B or vice versa.
INVERTED ‘V’ DIPOLE: where the center piece is raised higher than points A and B thus forming an angle with the vertex as the center piece.
However Dipoles are not favourable where there is limited installation space.
Little whip antennas, wire antennas in trees, and antennas atop a tower are all used, depending on the frequency in use. Lower frequencies have longer wavelengths. Longer wavelengths need larger antennas. The same antennas (used to transmit and receive) can be small, portable, put in trees or on the trunk of a car.
The common 146-MHz (2-meter) antenna is a 19-inch quarter-wave whip. A wavelength at 146 MHz is approximately 2 (300 divided by 146) meters, and a quarter wave of 2 meters is about 19 inches (50 cm). Hams enjoy the fun of experimenting with various types of antennas. Some antennas are made of wire strung between trees. Be sure to use lightning protection for outside antennas!
Hams, including the writer of this article, have communicated with other hams using the following types of antennas with antenna tuners:
Ø Metal window screens in upper floors of hotels and motels
Ø Aluminium extension ladders, insulated from the ground, leaning against a house (the lower the frequency, the longer the ladder)
Ø Soldered-together rain gutters and downspouts
Ø Flat copper "burglar-tape" hidden behind wallpapered walls
Ø Extended "Slinky" toys supported by a rope through the middle, in an attic
Ø Camera-tripod-supported whip antenna
Ø Disguised flagpoles fed with buried coaxial cable
Ø Fine wires cast with a fishing rod between dormitory buildings
FREQUENCY & WORKING
Hams use a variety of frequencies for communications. Non-hams can "listen in" via their own receivers or radio scanners. Hams are able to use many frequency bands across the radio spectrum -- these frequencies are allocated by the FCC for amateur use. Hams may operate from just above the AM broadcast band to the microwave region, in the gigahertz range. Many ham bands are found in the frequency range that goes from above the AM radio band (1.6 MHz) to just above the citizens band (27 MHz). During daylight, 15 to 27 MHz is a good band for long-distance communications. At night, the band from 1.6 to 15 MHz is good for long-distance communications. These bands are often referred to historically as short-wave bands (as in "short-wave radio"). Unlike frequencies used by FM radio stations and TV stations, which are line-of-sight and therefore limited to 40 or 50 miles, short-waves "bounce" off the ionosphere from the transmitter to the receiver's antenna. The higher the frequency is, the "shorter" the wavelength is.
Besides communicating by morse code or wire less telephony, amateurs are also permitted satellite communication, slow scan TV (SSTV) Fax & RadioTeletype. In the case of SSTV, still photos are sent one frame at a time. As the picture takes eight seconds to form, it is not possible to transmit moving pictures are now being transmitted on higher frequencies.
There are various satellites now in orbit, organized by International teams, using the most sophisticated equipments. More than 12 OSCARs are vice in orbit. OSCAR stands for "Orbiting Satellite Carrying Amateur Radio".
All the OSCAR's are built by amateur radio operators in
Most of the OSCARS are placed in orbit by the Aeronautics and Space Administration of the
Means of Communication Using Ham Radio
1. RTTY (Radio Teletype)
RTTY or RadioTeletype is a direct machine to machine communications mode using the Baudot (or Murray) code.
This mode became popular with many amateurs when surplus TTY machines became available at a reasonable cost after World War II. These mechanical monsters provided a keyboard for Input and a paper roll for printed Output. They were also useful to help hold the house down in times of hurricane winds - they must weigh a ton. Video displays were still too exotic and expensive in those days. It was not until the mid 1970s that we began to see the Video Display come into more widespread use. (By the way, have you ever wondered why early Program Languages like BASIC use the command PRINT to display their output?)
When transmitting Morse Code, the transmitter is switched on and off to make the dits and dahs. When sending Teletype however the transmitter rune continuously, sending either of two frequencies conventionally known as Mark and Space (a reference to paper tape reception of telegraphy). The early pioneers found on-off keying was not all that successful for Teletype signals because of interference from static.
They experimented with FSK, or Frequency Shift Keying and found it performed much better. With FSK, the transmitter is shifted up in frequency every time a Mark is to be sent, reverting to the lower frequency for a Space. The amount of the shift is usually 170 Hz for Amateur Radio use although many commercial Teletype signals use other shifts, notably 425 Hz and 85(} Hz.
Many systems use AFSK or Audio. Frequency Shift Keying. When this is sent, the transmitting station generates the Mark and Space audio tones and feeds them into the transmitters, microphone input. The result at the receiving end is that the same audio tones are heard and processed, whether the transmitting station used FSK or AFSK.
When listening to a teletype signal off air, you will soon get to recognize the familiar warble of Mark and Space tones.
In the modern amateur shack the TTY machine is usually,-i Multi-mode controller or PC interface cable connected to an HF transceiver which the operator tunes so that the received audio is just the right pitch or audio frequency to trigger the demodulator's Mark and Space response.
If the transceiver is slightly off the correct frequency the tones vary and the text becomes garbled or even lost altogether. To help the other station tune the receiver correctly, a RTTY operator can send a string of alternate R and Y characters RYRYRYRYRY. This pattern is chosen as it produces the most frequent and almost symmetrical alternation of Mark and Space tones, giving the receiving operator the best chance to tune the receiver before the "real" message starts. However, even if the signal is accurately tuned, the information can become garbled or completely lost due to interference, fading. or noise. Often, it is possible to make sense of the message even with parts missing, but RTTY is by NO means an error free mode! The new DSP based programs such as MMTTY, are able to decode RTTY signals with-much greater sensitivity than the older analog systems.
The Baudot code is a 5 bit code and those of you who are familiar with Binary Notation will know that the maximum number of values we can have with 5 bits is 32. That means that each unit of transmission, one keystroke if you like, can contain any one of 32 possible values. If you look up a table of Baudot codes you will see there are 32 values listed, one code for each letter of the alphabet plus a few other codes for other things such as a space and a Carriage Return. But, what if we want to send a number such as "9" or a question mark? These are not mentioned in that table because all 32 codes are already used.
The solution is rather similar to the Typewriter or Computer Keyboard where we have the Shift key to get various additional codes from the keyboard. Most keys will produce a different result if we hold down the Shift key as we type. Well, one of those original 32 codes is a special code known as FIGS (for Figures Shift). The convention is that when we want to send a number or some other special character such as a punctuation mark, we can do that by firstly transmitting a FIGS code.
Then instead of using that original table of 32 codes, we have a second table of codes to use, and that second table includes all ten numeric digits and various punctuation marks. Provided both sides of the conversation observe the convention, the sender can send a FIGS and start using the second table. The receiver will see the FIGS code and it too will interpret all data that follows from the second table.
With just 5 bits of data we then have almost 64 different codes we can send and receive. (I say almost because there is some duplication in the two tables, including a space and a Carriage Return but that is not important here). Even that many codes is not enough to handle all 26 letters of the alphabet in both UPPER and lower case, so RTTY systems always operate in upper case only.
If we wanted to type a big number (say "13579") we don't have to send FIGS before every digit. We send that code only once and the receiver then will take EVERYTHING we type from now as if it belongs in the second table. When we want to revert to the normal alphabetic table of codes we can send another special code, this one called LTRS (for Letters Shift). Then everything goes back to normal, using the original alphabetic table of codes.
Normally we don't have to concern ourselves with these FIGS and LTRS codes. Our computing equipment will take care of those things for us. We just type away and rely on the system to generate and send those codes when necessary.
It is quite possible to lose bits here and there when receiving a RTTY signal, whether it be because of fading, interference, frequency drift, or whatever. One of the big problems with lost data is the possible loss of a FIGS or LTRS code! Say we had sent "13579" and then typed "HAPPY BIRTHDAY". Our equipment would have sent a LTRS code before the first "H" but what if the receiver did not copy the LTRS code we sent? Can you imagine what happens? As far as the receiver is concerned we are still sending numbers or other codes from the numeric table! So our "HAPPY BIRTHDAY" is going to come out looking something like "#-006 ? 845#$-6". And EVERYTHING we type from then on is going to look just as strange until we happen to send another LTRS code later. It is for this reason that many systems include an option to "Un-shift on space". If you have a multi mode TNC capable of handling RTTY, you will probably have this in your TNC. If that option is ON then your receiving system will imply a LTRS code every time it receives a space. So if you seem to be copying lots of funny numbers from a strong, well tuned signal, try setting that option ON.
We can overcome some of these problems by using ASCII instead of using the Baudot code. With ASCII we can have 128 different codes so we do not need the FIGS/LTRS codes. All Personal Computers use ASCII as their native language so it would be a reasonable thing to use. Although not part of the defined ASCII standard, it has become an almost de-facto standard in the computer world that an additional 128 characters are available, often called Extended ASCII. But, despite these benefits, Baudot continues to rule the airwaves for amateur and Commercial Teletype transmissions.
Today, RTTY is still a popular mode especially on the HF bands, and the advent of the “Glass Terminal”, firstly the Dumb Terminal and now the Personal Computer, has brought this mode to eve more operators the world over. Many specialized RTTY systems were developed for the Amateur enthusiasts but have been superseded now by the Personal Computer with one f the Multi Mode TNCs or sound card DSP programs which handle RTTY and many other modes besides.
The latest Computerized RTTY equipment generally allows us to use the mode, better, quitter, more efficiently, using less power and occupying less space than the old TTY machines, but the limitations of the mode remain.
2. Digital Modes
MT63 is a new DSP based mode for sending keyboard text over paths that experience fading and interference from other signals. It is accomplished by a complex scheme to encode text in a matrix of 64 tones over time and frequency. This overkill method provides a "cushion" of error correction at the receiving end while still providing a 100 WPM rate. The wide bandwidth (1 KHz for the standard method) makes this mode less desirable on crowded ham bands such as 20 meters. A fast PC (166 MHz or faster) is needed to use all functions of this mode.
THROB is yet another new DSP sound card mode that attempts to use Fast Fourier Transform technology (as used by waterfall displays) to decode a 5 tone signal. The THROB program is an attempt to push DSP into the area where other methods fail because of sensitivity or propagation difficulties and at the same time work at a reasonable speed. The text speed is slower than other modes but the author (G3PPT) has been improving his MFSK (Multiple Frequency Shift Keying) program. Check his web site for the latest developments.
MFSKIf is an advancement to the THROB mode and encodes 16 tones. The PC sound card for DSP uses Fast Fourier Transform technology to decode the ASCII characters, and Constant Phase Frequency Shift Keying to send the coded signal. Continuous Forward Error Correction (FEC) sends all data twice with an interleaving technique to reduce errors from impulse noise and static crashes. A new improved Varicode is used to increase the efficiency of sending extended ASCII characters, making it possible to transfer short data files between stations under fair to good conditions. The relatively wide bandwidth (316 Hz) for this mode allows faster baud rates (typing is about 42 WPM) and greater immunity to multi path phase shift. A second version called MFSK8 is available with a ,' lower baud rate (8) but greater reliability for DXing when polar phase shift is a major problem. Both versions are available in a nice freeware Windows program created by TZ8BLY.
NOTES:
Frequency-shift keying (FSK) shifts between two known states. Phase-shift keying (PSK) changes PHASE of a signal against some reference. FSK is sent by either shifting a carrier frequency (FIB) or modulating SSB(Single Side Band) with two shifting audio tones (AFSK). When sending PSK, a complex audio waveform is transmitted by SSB. Tracking is much more critical for PSK, thus requiring more frequency stability.
DSP (Digital Signal Processing) techniques use high speed processing to convert audio into digital coding, so that a program can manipulate the coded audio in ways not possible with traditional hardware filters. The 16 and 32 bit sound cards found in modern PCs provide this capability. FUZZY MODES are those modes that allow the human eye/ear/brain to be used to its maximum potential. In order to do this, a number of rules are required, to ensure that any electronics or logic circuitry is not allowed to make decisions which may be less inspired than human decisions. Examples of potentially Fuzzy modes are Morse Code, HFFAX, SSTV and Hellschreiber. The rules are:
Ø The transmissions must be uncoded. (The signal is sent as a real-time language.)
Ø The receiver must not decide when data is present. (Untouched by any prior decisions.)
Ø The receiver must not decide what data is present. (It must be presented as received.)
3. Morse Code
It is often asked why Morse is necessary. In spite of all the advances in telephony, Morse still remains the international language for radio operators. It is easily intelligible because of several recognized code and abbreviations and its ability to cover long distance with lower power and its ability to break through interferences. It is usually possible to communicate with Morse when radio telephony becomes unintelligible.
However, recently, with the rapid advancement communication technology, it is being seriously considered by the ITU (International Telecommunication Union) whether learning it is now really relevant, as it can be transmitted and received electronically.
For grades of licenses you have to pass a Morse test. This is generally considered a major hurdle. But it need not be if you go about it scientifically and with a little determination.
The Morse code has been designed with a combination of dotes and dashes known as dits and dahs to denote letter, numericals and punctuation marks.
The first thing to remember is that you are learning a new language-the language of sound. Therefore right from the beginning avoid getting into the habit of memorizing dots and dashes, but learn to listen to the sound of the letters. Progress maybe slow in the beginning but if you totally immerse yourself in this activity for two months - to the exclusion of cinemas, visiting friends, reading novels, etc. you will emerge an experienced code operator before you realize it. Two months of total dedication are needed. During that time speak morse, dream morse, see morse for every sign board you pass. Imagine morse for every word you speak or hear. Whistle it while walking or pronounce the letters by hissing or buzzing. This may seem a tall order but it much better than going about it half heartedly and getting dejected, deciding part way through that you will never learn and give it up. Practice seriously at least half hour a day, besides thinking about it the whole day.
:
"The International Morse Code, is built up of three elements: the dot, or short signal; the dash, or long signal; and the space. Letters and figures are represented by various combinations of dots and dashes. The dot is the basic unit. The dash is equal in length to three dots and the spacing between these elements of the character is equal in length to one dot. Between characters the spacing equals three dots and between words or groups or groups five dots.
As wireless reception is concerned with sound signals, the aim should be to memorize rhythmic sounds rather than graphical symbols. In other words, the letter "A" (._) should be associated with the idea of a short sound followed by a longer one; it should not conjure up a mental picture of a short and long mark on paper. This is why most of the aids to memory that have been put forward, ingenious as soon of them are, do not fully meet the case. As a rule, they encourage the learner to form a graphical conception of the symbols that will be positively harmful to his progress as everything must be unlearned when he comes to the next stage and is concerned solely with sounds."
The alphabets, numerals:
A-di-dah S-di-di-dit
B-dah-di-di-di T-dah
C-dah-di-dah-dit U-di-di-dah
D-dah-di-dit V-di-di-di-dah
E-dit W-di-dah-dah
F-di-di-dah-dit X-dah-di-di-dah
G-dah-dah-dit Y-dah-di-dah-dah
H-di-di-di-dit Z-dah-dah-di-dit
I-di-dit 1-di-dah-dah-dah-dah
J-di-dah-dah-dah 2-di-di-dah-dah-dah
K-dah-di-dah 3-di-di-di-dah-dah
L-di-dah-di-dit 4-di-di-di-di-dah
M-dah-dah 5-di-di-di-di-dit
N-dah-dit 6-dah-di-di-di-dit
O-dah-dah-dah 7-dah-dah-di-di-dit
P-di-dah-dah-dit 8-dah-dah-dah-di-dit
Q-dah-dah-di-dah 9-dah-dah-dah-dah-dit
R-di-dah-dit 0-dah-dah-dah-dah-dah
You will notice that we have not used dots and dashes to depict the letters because they form a visual image. Instead we have used di and dah which when pronounced should convey only a sound image. These are practiced so that the sound of each letter should produce the image of the letter.
For instance the sound dah-dah-dit must instantly bring to mind the letter G, and so on. If it is memorized as dots and dashes you will, on hearing the signal, visualize two dashes and a dot and convert it to a visual picture and then into a letter. Moreover it is dangerous to try to memorize groups of similar letters or opposites as this creates a double thinking process.. Also, do not attempt to learn the letters alphabetically for similar reasons. Do not attempt to send until you can recognize each letter at slow speed.
When you are ready to transmit, get a Morse key and a 'code practice oscillator'. A CPO is easy to construct and numerous diagrams have been published in books and magazines. However keys and CPO are also available ready made from ARSI. In sending, rest your arm comfortably n the table and with the underside of the wrist touching the table. Now hold the key with your thumb and two fingers, tightly. The up and down movement must be only from the wrist. The whole hand and arm should not move.
Short of a training class it is useful to have a friend send to you and receive from you. When receiving if you are doubtful about a letter immediately forget about it and concentrate on the next one. Never waste time trying to remember it as you will then miss a number of others. Never look back on what you have written and never anticipate a letter.
Most books on Morse give a series of code groups which are useful for practicing.
There are also many different types of tapes, records and other teaching aids available abroad.
ADVANTAGES
Ø Ham radio operators (Hams) can communicate with each other independently, any where in the world, anytime in any situation.
Ø Hams don’t need any transmitting or receiving stations to help in communication.
Ø Hams can communicate even when other means of communication have been overloaded or destroyed.
Ø The setting of a ham radio station is very simple and fast.
Ø A dipole antenna can be made anywhere between two trees.
Ø The instruments for making the station, antenna and ham radio are easily available in the market. (Between $100 to $1000)
Ø The process of getting the license to become an amateur radio operator is very easy.
Ø As ham radios are battery operated they are convenient to use in emergencies.
Thus amateur radio operators can handle critical emergency traffic out of the affected disaster areas when normal communications were knocked out or overloaded.
Ø Hurricanes
Ø Earthquakes
Ø Tornadoes and floods
Ø Motorist accidents
Ø Fires and chemical spills
Ø Search and rescues
The recent social service provided by the hams is,
Ø Latur Earthquake in October 1993. On this occasion hams of
Ø The communication provided by hams during the Morvi dam disaster was a landmark effort.
Ø The outstanding work done by
Ø The devastating earthquake in Bhuj in January 2001.
Ø During the wars in 1965 and 1971 with
Ø Internationally, during the Alpine Viejas Fire.
Ø The earthquakes in
Ø Hurricane disasters in
Ø The Sept 11 Attack in
DISADVANTAGES
Ø Cordless phones of higher frequency ranges, available in the market may interfere with the communicating frequency of hams.
Ø They are quite heavy and large in comparison with other means of communication such as cell phones.
TO DOWN LOAD REPORT AND PPT
