What is broadcasting? What is broadcasting?

The beginning of radio at a frequency of one megahertz (1 MHz). These electromagnetic So, how can sound be transmitted by radio? The simplest way to do waves travel at the speed of light. (We now know that light itself is an it is to vary the strength (or amplitude) of the radio signal to match The first radio transmission was made in 1895. It did not carry audio electromagnetic wave.) Note that one full wave or oscillation involves the variation in amplitude of the audio signal. This process is called signals (voice or music) but consisted of just short bursts of a fixed two changes of direction. ‘amplitude modulation’ or AM. Note that the frequency of the transmitted radio frequency using Morse code. Morse code had been in use from radio signal is fixed; only its amplitude changes. A radio transmitter the 1840s to send messages via telegraph wires. The code consists of therefore does not actually transmit sound but only an inaudible short and long pulses, commonly known as dots and dashes, and may From Morse code to analogue radio electromagnetic wave. A radio receiver detects the radio frequency and be represented by electrical signals or flashes of light. For example, the Maconi’s original radio transmitters and receivers were intended to from the variation in its amplitude it can reconstruct the audio signal. code for ‘S’ is • • • and the code or ‘O’ is — — —. The code for SOS is replace wired telegraphy with wireless telegraphy. His radio signals ComReg is the statutory body responsible for the regulation therefore • • • — — — • • •. were detected by a relatively simple circuit which would activate an Further developments of the electronic communications sector (telecommunications, electromagnet or turn on a small light when a burst of radio frequency radiocommunications and broadcasting transmission) and Magnetic and electric fields signal was picked up by a large receiving antenna. In 1897 he built a AM radio signals are prone to interference from electric motors, number of transmitters on the south coast of England for communication fluorescent lamps, electric cables and from other radio stations. During the postal sector. Its remit covers all kinds of transmission An electric current in a conductor (e.g. a copper wire) produces a with ships. the 1950s, a number of frequency modulation (FM) systems were networks including: magnetic field around the wire. If the evaluated and in 1961 one became the standard. FM radio requires • Traditional telephone wire current is reversed then the magnetic In 1907 the first commercial transatlantic wireless telegraph service was more complex electronics in both the transmitter and receiver. However, field is also reversed. This effect, which set up by Marconi between stations at Clifden, Ireland, and Glace Bay in the sound quality is generally better than AM and it can be used for • Television and radio frequencies oscillator oscillator was discovered by Ørsted in 1831, is Newfoundland. The power of the Clifden transmitter was 150,000 watts. stereo broadcasts. • Radiocommunications including fixed wireless easy to demonstrate. Wireless voice communication was first demonstrated publicly in 1900 by One significant disadvantage of FM results from its higher frequency and • Mobile operators providing voice and data services The strength of the magnetic field Roberto Landell de Moura (in Brazil). In 1920 regular radio transmission consequent shorter wavelength than AM. (Remember that the wavelength • Satellite services decreases as the cube of the distance from the wire increases (if the for the public started; broadcasting had begun. Initially the audiences = 300,000,000 ÷ frequency). Shorter waves diffract less around large ComReg enables competition in the communications sector distances are large compared with the length of the wire). For example, were small because relatively few people had radio receivers. Crystal objects such as mountains and so FM reception may be poor in valleys the magnetic field strength at a distance of one kilometre is a millionth of radios could be bought or made but they required headphones and unless extra transmitters are installed. (This problem is more pronounced by facilitating market entry for networks and services and by its strength at a distance of ten metres. were little more than a curiosity. The BBC radio service began in 1922. in the case of mobile phones, which use even shorter wavelengths.) regulating access to networks so as to ensure that consumers, Ireland’s national radio station, known as 2RN, began broadcasting from In a similar way, opposite electric charges both business and residential, have choice in the services which McKee Barracks in Dublin, on 1st January 1926. have an associated electric field, the AM radio FM radio TV Mobile they wish to use. In a rapidly evolving sector, both in technological direction of which is designated as ‘positive and commercial terms, ComReg provides the framework for the to negative’, as shown in the diagram. If the How can audio be transmitted? 200 – 1600 88 – 108 300 – 3000 900 MHz or introduction of new services such as next generation mobile to + frequency charges are reversed then the direction of the + Sound normally enters our ears as rapid air pressure variations. kHz MHz MHz 1800 MHz support smartphones and similar applications. electric field is reversed. Audible frequencies range from about 16 Hz to 16,000 Hz. Sound is Encouraging innovation is also a key role for ComReg. + oscillator not electromagnetic; it is a propagated disturbance of a medium. In air 34 cm or But how quickly are these effects propagated? wavelength 1500 – 19 m 3.4 – 2.8 m 1 – 0.1 m This covers both regulatory innovations, such as Do the changes occur instantly or do they take + it travels about 330 metres per second. In contrast, radio signals are 17 cm implementation of market reviews under the new European some– time to travel? Can the effects travel electromagnetic; they do not require a medium and they travel at about oscillator Typical frequencies and wavelengths of radio signals regulatory framework, and technical innovations. On the radio faster than light? – 300 million metres per second. The frequency of radio signals ranges from about 100 kHz to beyond 1000 MHz. spectrum side the role involves development of strategies for In the early 1930s a few different systems were devised to transmit management and use of the radio spectrum, new initiatives – How is a radio signal moving images by means of radio waves; television was born. In 1936 in the wireless licensing area, and the promotion of Ireland transmitted? – the BBC began regular television broadcasts. RTÉ began broadcasting as a test bed for innovative uses of spectrum (See Test & Trial Ireland at www.testandtrial.ie). ComReg publishes the Consider an antenna (aerial) made of two vertical conductors attached black and white TV in 1961 and by 1971 it was broadcasting colour to variable voltage source as shown in the diagram. When it is switched Radio frequency signal (the ‘carrier’) TV (PAL). following websites, offering a wide range of information on, almost instantly the top part becomes positively charged and the The first communications satellite, Telstar 1, was launched in 1962. and advice to users. bottom part becomes negatively charged. In that brief instant while the It could relay just one television channel or a number of phone calls. Advice for communications consumers charges are moving a magnetic field is It did not provide a direct broadcast service to the public. set up. Once the charges are established www.askcomreg.ie no further charge moves (i.e. there is no The digital revolution Interactive guide on phone and broadband pricing longer any electric current) and so the Audio signal www.callcosts.ie Direct digital satellite broadcasting began in the late 1980s. magnetic field strength drops to zero. oscillator The satellites involved were placed in geostationary orbits and so the Information on Premium Rate services At the same time an electric field is set receiving dishes can be placed in fixed positions. up between the positive and negative www.phonesmart.ie charges. This field is perpendicular to In the 1990s digital terrestrial TV (DTT) broadcasts began. Initially Statistical information on the Irish electronic the magnetic field. If the aerial is vertical Modulated RF signal the service was experimental and operated alongside the analogue TV communications market Magnetic field of a dipole transmissions but it gradually replaced the older system. In the European then the magnetic field is horizontal and the www.comstat.ie electric field is vertical; in this case antenna Union analogue TV broadcasts were phased out in 2012. Find out more about the work of ComReg at www.comreg.ie the propagated wave is said to be The main advantage of digital transmission is that several TV channels vertically polarised. can be broadcast on one frequency at the same time and so more efficient use is made of the available bandwidth. If the voltage source is reversed then the magnetic and electric fields Find this and other lessons on www.sta.ie reverse. If this happens two million times per second then the aerial radiates alternating electric and magnetic fields, i.e. ‘radio waves’, + Rectified RF signal +

oscillator

– Recovered audio signal –

Antenna

coil headphones tuning capacitor diode rectifier What is broadcasting? What is broadcasting?

The beginning of radio at a frequency of one megahertz (1 MHz). These electromagnetic So, how can sound be transmitted by radio? The simplest way to do waves travel at the speed of light. (We now know that light itself is an it is to vary the strength (or amplitude) of the radio signal to match The first radio transmission was made in 1895. It did not carry audio electromagnetic wave.) Note that one full wave or oscillation involves the variation in amplitude of the audio signal. This process is called signals (voice or music) but consisted of just short bursts of a fixed two changes of direction. ‘amplitude modulation’ or AM. Note that the frequency of the transmitted radio frequency using Morse code. Morse code had been in use from radio signal is fixed; only its amplitude changes. A radio transmitter the 1840s to send messages via telegraph wires. The code consists of therefore does not actually transmit sound but only an inaudible short and long pulses, commonly known as dots and dashes, and may From Morse code to analogue radio electromagnetic wave. A radio receiver detects the radio frequency and be represented by electrical signals or flashes of light. For example, the Maconi’s original radio transmitters and receivers were intended to from the variation in its amplitude it can reconstruct the audio signal. code for ‘S’ is • • • and the code or ‘O’ is — — —. The code for SOS is replace wired telegraphy with wireless telegraphy. His radio signals ComReg is the statutory body responsible for the regulation therefore • • • — — — • • •. were detected by a relatively simple circuit which would activate an Further developments of the electronic communications sector (telecommunications, electromagnet or turn on a small light when a burst of radio frequency radiocommunications and broadcasting transmission) and Magnetic and electric fields signal was picked up by a large receiving antenna. In 1897 he built a AM radio signals are prone to interference from electric motors, number of transmitters on the south coast of England for communication fluorescent lamps, electric cables and from other radio stations. During the postal sector. Its remit covers all kinds of transmission An electric current in a conductor (e.g. a copper wire) produces a with ships. the 1950s, a number of frequency modulation (FM) systems were networks including: magnetic field around the wire. If the evaluated and in 1961 one became the standard. FM radio requires • Traditional telephone wire current is reversed then the magnetic In 1907 the first commercial transatlantic wireless telegraph service was more complex electronics in both the transmitter and receiver. However, field is also reversed. This effect, which set up by Marconi between stations at Clifden, Ireland, and Glace Bay in the sound quality is generally better than AM and it can be used for • Television and radio frequencies oscillator oscillator was discovered by Ørsted in 1831, is Newfoundland. The power of the Clifden transmitter was 150,000 watts. stereo broadcasts. • Radiocommunications including fixed wireless easy to demonstrate. Wireless voice communication was first demonstrated publicly in 1900 by One significant disadvantage of FM results from its higher frequency and • Mobile operators providing voice and data services The strength of the magnetic field Roberto Landell de Moura (in Brazil). In 1920 regular radio transmission consequent shorter wavelength than AM. (Remember that the wavelength • Satellite services decreases as the cube of the distance from the wire increases (if the for the public started; broadcasting had begun. Initially the audiences = 300,000,000 ÷ frequency). Shorter waves diffract less around large ComReg enables competition in the communications sector distances are large compared with the length of the wire). For example, were small because relatively few people had radio receivers. Crystal objects such as mountains and so FM reception may be poor in valleys the magnetic field strength at a distance of one kilometre is a millionth of radios could be bought or made but they required headphones and unless extra transmitters are installed. (This problem is more pronounced by facilitating market entry for networks and services and by its strength at a distance of ten metres. were little more than a curiosity. The BBC radio service began in 1922. in the case of mobile phones, which use even shorter wavelengths.) regulating access to networks so as to ensure that consumers, Ireland’s national radio station, known as 2RN, began broadcasting from In a similar way, opposite electric charges both business and residential, have choice in the services which McKee Barracks in Dublin, on 1st January 1926. have an associated electric field, the AM radio FM radio TV Mobile they wish to use. In a rapidly evolving sector, both in technological direction of which is designated as ‘positive and commercial terms, ComReg provides the framework for the to negative’, as shown in the diagram. If the How can audio be transmitted? 200 – 1600 88 – 108 300 – 3000 900 MHz or introduction of new services such as next generation mobile to + frequency charges are reversed then the direction of the + Sound normally enters our ears as rapid air pressure variations. kHz MHz MHz 1800 MHz support smartphones and similar applications. electric field is reversed. Audible frequencies range from about 16 Hz to 16,000 Hz. Sound is Encouraging innovation is also a key role for ComReg. + oscillator not electromagnetic; it is a propagated disturbance of a medium. In air 34 cm or But how quickly are these effects propagated? wavelength 1500 – 19 m 3.4 – 2.8 m 1 – 0.1 m This covers both regulatory innovations, such as Do the changes occur instantly or do they take + it travels about 330 metres per second. In contrast, radio signals are 17 cm implementation of market reviews under the new European some– time to travel? Can the effects travel electromagnetic; they do not require a medium and they travel at about oscillator Typical frequencies and wavelengths of radio signals regulatory framework, and technical innovations. On the radio faster than light? – 300 million metres per second. The frequency of radio signals ranges from about 100 kHz to beyond 1000 MHz. spectrum side the role involves development of strategies for In the early 1930s a few different systems were devised to transmit management and use of the radio spectrum, new initiatives – How is a radio signal moving images by means of radio waves; television was born. In 1936 in the wireless licensing area, and the promotion of Ireland transmitted? – the BBC began regular television broadcasts. RTÉ began broadcasting as a test bed for innovative uses of spectrum (See Test & Trial Ireland at www.testandtrial.ie). ComReg publishes the Consider an antenna (aerial) made of two vertical conductors attached black and white TV in 1961 and by 1971 it was broadcasting colour to variable voltage source as shown in the diagram. When it is switched Radio frequency signal (the ‘carrier’) TV (PAL). following websites, offering a wide range of information on, almost instantly the top part becomes positively charged and the The first communications satellite, Telstar 1, was launched in 1962. and advice to users. bottom part becomes negatively charged. In that brief instant while the It could relay just one television channel or a number of phone calls. Advice for communications consumers charges are moving a magnetic field is It did not provide a direct broadcast service to the public. set up. Once the charges are established www.askcomreg.ie no further charge moves (i.e. there is no The digital revolution Interactive guide on phone and broadband pricing longer any electric current) and so the Audio signal www.callcosts.ie Direct digital satellite broadcasting began in the late 1980s. magnetic field strength drops to zero. oscillator The satellites involved were placed in geostationary orbits and so the Information on Premium Rate services At the same time an electric field is set receiving dishes can be placed in fixed positions. up between the positive and negative www.phonesmart.ie charges. This field is perpendicular to In the 1990s digital terrestrial TV (DTT) broadcasts began. Initially Statistical information on the Irish electronic the magnetic field. If the aerial is vertical Modulated RF signal the service was experimental and operated alongside the analogue TV communications market Magnetic field of a dipole transmissions but it gradually replaced the older system. In the European then the magnetic field is horizontal and the www.comstat.ie electric field is vertical; in this case antenna Union analogue TV broadcasts were phased out in 2012. Find out more about the work of ComReg at www.comreg.ie the propagated wave is said to be The main advantage of digital transmission is that several TV channels vertically polarised. can be broadcast on one frequency at the same time and so more efficient use is made of the available bandwidth. If the voltage source is reversed then the magnetic and electric fields Find this and other lessons on www.sta.ie reverse. If this happens two million times per second then the aerial radiates alternating electric and magnetic fields, i.e. ‘radio waves’, + Rectified RF signal + oscillator

– Recovered audio signal –

Antenna

coil headphones tuning capacitor diode rectifier RadioRadio frequency frequency signal signal (the (the ‘carrier’) ‘carrier’)

AudioAudio signal signal

ModulatedModulated RF RF signal signal

WhatWhat is is broadcasting? broadcasting? What is broadcasting?

RectifiedRectified RF RF signal signal

SyllabusSyllabus References References StudentStudent Activities Activities ExaminationExamination Questions Questions DidDid You You Know? Know? TheThe main main syllabus syllabus references references for for the the lesson lesson are: are: 1. 1. In Inthe the early early days days of ofradio radio broadcasting broadcasting (1920s) (1920s) so so called called “crystal “crystal • • TheThe original original use use of of the the term term “broadcasting” “broadcasting” was was in inagriculture. agriculture. LeavingLeaving Certificate Certificate Physics Physics (OL) (OL) 2002 2002 Q. Q.7 7 ManyMany crop crop plants plants are are sown sown in inrows rows or or drills drills to to facilitate facilitate harve harvesting.sting. LeavingLeaving Certificate Certificate Physics Physics (pp. (pp. 30-33) 30-33) sets”sets” were were commonly commonly used used to topick pick up up the the transmissions. transmissions. Apart Apart from from TheThe following following table table gives gives examples examples of of electromagnetic electromagnetic waves waves and and However,However, grass grass seeds seeds are are generally generally scattered scattered more more widely widely and and • • Wave Wave phenomena: phenomena: reflection, reflection, refraction, refraction, diffraction, diffraction, interference, interference, headphonesheadphones these these devices devices typically typically had had just just three three components: components: theirtheir typical typical wavelengths. wavelengths. randomlyrandomly ― ― a apractice practice known known as as broadcasting. broadcasting. polarisation.polarisation. Everyday Everyday examples, examples, e.g. e.g. radio radio waves, waves, waves waves at at a coila coil of ofinsulated insulated wire, wire, a capacitora capacitor and and a crystala crystal which which acted acted as as a a RecoveredRecovered audio audio signal signal • • TelephoneTelephone calls calls are are usually usually ‘one ‘one to to one’ one’ and and are are bidirectional. bidirectional. sea,sea, seismic seismic waves. waves. diode.diode. Find Find out out more more about about crystal crystal radios radios on on websites websites such such as: as: micro-micro- InIn contrast, contrast, radio radio and and TV TV broadcasting broadcasting is isa a‘one ‘one to to many’ many’ process process wavewave radioradio infraredinfrared light light ultraviolet ultraviolet • • Longitudinal Longitudinal and and transverse transverse waves: waves: frequency, frequency, amplitude, amplitude, https://en.wikipedia.org/wiki/Crystal_radiohttps://en.wikipedia.org/wiki/Crystal_radio wavewave andand is isunidirectional. unidirectional. TheThe coil coil + +capacitor capacitor (in (in parallel) parallel) acted acted as as a ‘tuneda ‘tuned circuit’ circuit’ which which wavelength,wavelength, velocity. velocity. Relationship Relationship c =c =f λ.f λ. • • TheThe Athlone Athlone radio radio transmitter transmitter was was opened opened in in1932, 1932, broadcasting broadcasting wouldwould respond respond best best to toone one frequency. frequency. The The diode diode rectified rectified the the wavelengthwavelength 100100 m m 0.1 0.1 m m 1 μm 1 μm 600 600 nm nm 10 10 nm nm onon 567 567 kHz kHz (i.e. (i.e. in inthe the ‘medium ‘medium wave’ wave’ band). band). Its Its name name was was • • The The electromagnetic electromagnetic spectrum: spectrum: Relative Relative positions positions of of radiations radiations in in alternatingalternating radio radio frequency frequency oscillation oscillation which which could could then then be be termsterms of of wavelength wavelength and and frequency. frequency. • • Name Name one one property property that that all all of of these these waves waves have have in incommon. common. changedchanged from from Radio Radio Athlone Athlone to to Radio Radio Éireann Éireann in in1937. 1937. It Itwas was ‘smoothed’‘smoothed’ slightly slightly by by a seconda second (small) (small) capacitor. capacitor. replacedreplaced by by the the Tullamore Tullamore transmitter transmitter in in1975. 1975. That That too too was was • • Polarisation Polarisation of of transverse transverse waves: waves: Demonstration Demonstration of of polarisation polarisation • • What What is isthe the frequency frequency of of the the radio radio waves? waves? switched-offswitched-off in in2008. 2008. The The only only remaining remaining AM AM broadcast broadcast by by RTÉ RTÉ (of(of light) light) using using polaroids polaroids or or other other suitable suitable method. method. AntennaAntenna • • Describe Describe how how infrared infrared radiation radiation can can be be detected. detected. (at(at least least until until 2017) 2017) is ison on 252 252 kHz kHz (longwave) (longwave) transmitting transmitting fro fromm ScienceScience and and Technology Technology in in Action Action is isalso also widely widely used used by by • • Give Give two two uses uses of of microwaves. microwaves. Clarkstown,Clarkstown, Co Co Meath. Meath. TransitionTransition Year Year classes. classes. TheThe speed speed of of light light is is3 3× ×10 108 m8 m s–1 s.–1 (.c ( =c =fλ )fλ)

coilcoil headphonesheadphones LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2006 2006 Q. Q.12 12b b BiographicalBiographical Notes Notes tuningtuning capacitor capacitor diodediode rectifier rectifier TheThe diagram diagram shows shows the the relative relative positions positions of of electromagnetic electromagnetic LearningLearning Outcomes Outcomes radiationsradiations in interms terms of of their their wavelength. wavelength. ReginaldReginald Fessenden Fessenden 1866 1866 - 1932- 1932 MakeMake a postera poster that that illustrates illustrates the the operation operation of ofa crystala crystal radio radio. . ReginaldReginald Fessenden Fessenden was was born born in inQuebec, Quebec, OnOn completion completion of of this this lesson, lesson, students students should should be be able able to: to: gammagamma micro-micro- NoteNote that that the the basic basic principles principles of oftuned tuned circuits circuits apply apply to tomodern modern radio radio A A UVUV lightlight IR IR B B Canada,Canada, in in1866. 1866. At At the the age age of offourteen fourteen he he raysrays waveswaves • • explain explain the the general general principles principles of of radio radio freqeuncy freqeuncy transmission transmission andand television television receivers, receivers, mobile mobile phones phones and and wifi wifi communication. communication. waswas employed employed as as a mathematicsa mathematics teacher teacher for for • • calculate calculate the the wavelength wavelength of of an an electomagnetic electomagnetic wave wave given given the the 2. 2. On On the the following following website website there there is isa tablea table of ofradio radio transmitters transmitters in inthe the • • Name Name the the radiations radiations marked marked A Aand and B. B. thethe younger younger pupils pupils while while he he was was studying studying in in frequency,frequency, and and vice vice versa versa MunsterMunster area. area. The The power power of ofsome some transmitters transmitters is isover over 100,000 100,000 watts watts • • Give Give one one property property which which is iscommon common to to all all electromagnetic electromagnetic thethe University. University. • • explain explain what what is ismeant meant by by amplitude amplitude mudulation mudulation whilewhile others others are are around around 20 20 watts. watts. What What do do you you notice notice about about the the radiations.radiations. AtAt the the age age of oftwenty twenty he he applied applied for for a joba job with with • • outline outline the the advanages advanages and and disadvantages disadvantages of of using using higher higher radio radio locationlocation of ofthe the high high power power transmitters? transmitters? • • Which Which one one of of the the radiations radiations has has the the shortest shortest wavelength? wavelength? ThomasThomas Edison Edison and, and, though though he he was was turned turned down down frequencies.frequencies. http://homepage.eircom.net/~fm_radio/munsterFM.htmlhttp://homepage.eircom.net/~fm_radio/munsterFM.html • • Describe Describe how how IR IR radiation radiation is isdetected. detected. at atfirst first he hewas was eventually eventually successful. successful. He Hegained gained • • Give Give one one use use for for microwaves. microwaves. valuablevaluable practical practical experience experience there. there. When When he he was was 24 24 he he was was appo appointedinted professorprofessor of ofElectrical Electrical Engineering Engineering at atPurdue Purdue University. University. True/FalseTrue/False Questions Questions LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2005 2005 Q. Q.6 6 In In1898-99 1898-99 he he successfully successfully developed developed a wirelessa wireless telephone telephone syste system.m. GeneralGeneral Learning Learning Points Points A Asatellite satellite transmits transmits radio radio signals signals to to earth. earth. At At a aparticular particular time time the the WhenWhen he he learned learned of ofMarconi’s Marconi’s work work he he realised realised that that he he could could make make a a a)a) The The first first radio radio transmission transmission was was mademade in in 1875. 1875. T T F F satellitesatellite is is1.2 1.2 × ×10 1012 12m m from from Earth. Earth. How How long long does does it takeit take the the signal signal TheseThese are are additional additional relevant relevant points points which which are are toto travel travel to to earth? earth? It Itis isnoticed noticed that that the the frequency frequency of of the the re receivedceived radio radio muchmuch more more efficient efficient system. system. In In1900 1900 he hebegan began work work for for the the US US WeatherWeather usedused to to extend extend knowledge knowledge and and facilitate facilitate discussion. discussion. b)b) Radio Radio wavelengths wavelengths are are typically typically less less than than 1 1mm. mm. T T F F signalsignal changes changes as as the the satellite satellite orbits orbits Saturn. Saturn. Explain Explain why. why. BureauBureau to toset set up up radio radio stations stations to totransmit transmit weather weather data. data. He He re receivedceived • • An An electric electric current current in ina aconductor conductor has has an an associated associated magnetic magnetic c)c) The The direction direction of of polarisation polarisation of of electromagnetic electromagnetic waves waves hundredshundreds of ofpatents patents for for his his inventions, inventions, including including the the continuou continuous waves wave (universal(universal gravitational gravitational constant constant = =6.7 6.7 × ×10 10–11–11 N Nm m2 kg2 kg–2;–2 ; field.field. WhenWhen the the current current stops stops the the magneticmagnetic field field disappears, disappears, is isthat that of of the the electric electric field. field. T T F F transmitter.transmitter. In InJanuary January 1906 1906 he he succeeded succeeded in inmaking making the the first first two-way two-way massmass of of Saturn Saturn = =5.7 5.7 × ×10 1026 26kg; kg; speed speed of of light light = =3.0 3.0 × ×10 108 m8 m s–1 s)–1) butbut the the effect effect takes takes time time to to propagate. propagate. d)d) A Aradio radio antenna antenna radiates radiates electric electric and and magnetic magnetic fields. fields. T T F F transatlantictransatlantic transmission transmission of ofMorse Morse code. code. • • Opposite Opposite electric electric charges charges have have an an associated associated electric electric field. field. e)e) Radio Radio signals signals do do not not travel travel as as fast fast as as light. light. T T F F LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2004 2004 Q. Q.5 (f)5 (f) • • If Ifan an alternating alternating potential potential is isapplied applied to to an an aerial aerial it radiatesit radiates electromagneticelectromagnetic waves. waves. f) f) The The frequency frequency of of AM AM broadcasts broadcasts is isgenerally generally much much lower lower WhatWhat is ismeant meant by by polarisation polarisation of of waves? waves? thanthan fhe fhe frequencies frequencies used used for for FM. FM. T T F F • • The The first first radio radio transmitters transmitters were were used used to to send send messagesmessages ReviseRevise The The Terms Terms (telegrams)(telegrams) using using Morse Morse code. code. g)g) AM AM broadcasts broadcasts are are being being phased phased out out because because they they are are not not JuniorJunior Certificate Certificate Science Science (HL) (HL) 2005 2005 CanCan you you recall recall the the meaning meaning of ofthe the following following terms? terms? • • Radio Radio signals signals are are elctromagnetic elctromagnetic and and so so cannot cannot be be heard. heard. asas effective effective in inmountainous mountainous areas. areas. T T F F Q.Q. 1 1 RevisingRevising terminology terminology is isa powerfula powerful aid aid to torecall recall and and retention. retention. InIn order order to to transmit transmit speech speech or or music music the the radio radio signal signal is is h)h) The The wavelength wavelength of of a a1 1MHz MHz electromagnetic electromagnetic wave wave is is (j)(j) The The diagram diagram shows shows a acurrent current carrying carrying modulatedmodulated either either in inamplitude amplitude or or frequency. frequency. wirewire passing passing through through a acard. card. aerial,aerial, amplitude amplitude modulation, modulation, antenna, antenna, bandwidth, bandwidth, broadcasting, broadcasting, crystal crystal 300300 metres. metres. T T F F radio,radio, cube, cube, diffract, diffract, digital digital terrestrial, terrestrial, direct direct digital digital satellite, satellite, electric electric field, field, • • Satellites Satellites are are now now used used to to relay relay television, television, radio, radio, phone phone and and i) i) Digital Digital broadcasting broadcasting makes makes more more efficient efficient use use of ofthe the electromagneticelectromagnetic waves, waves, frequency frequency modulation, modulation, geostationary geostationary orbi orbits,ts, faxfax messages. messages. ShowShow a amagnetic magnetic field field line line on on the the availableavailable bandwidth. bandwidth. T T F F cardcard in inthe the diagram diagram with with direction direction headphones,headphones, magnetic magnetic field, field, megahertz, megahertz, Morse Morse code, code, radio radio frequen frequency,cy, clearlyclearly indicated. indicated. CardCard television,television, vertically vertically polarised, polarised, wired wired telegraphy. telegraphy. CheckCheck your your answers answers to to these these questions questions on on www.sta.ie. www.sta.ie. CheckCheck the the Glossary Glossary of of terms terms for for this this lesson lesson on on www.sta.ie www.sta.ie RadioRadio frequency frequency signal signal (the (the ‘carrier’) ‘carrier’)

AudioAudio signal signal

ModulatedModulated RF RF signal signal

WhatWhat is is broadcasting? broadcasting? What is broadcasting?

RectifiedRectified RF RF signal signal

SyllabusSyllabus References References StudentStudent Activities Activities ExaminationExamination Questions Questions DidDid You You Know? Know? TheThe main main syllabus syllabus references references for for the the lesson lesson are: are: 1.1. In Inthe the early early days days of of radio radio broadcasting broadcasting (1920s) (1920s) so so called called “crystal “crystal • • TheThe original original use use of of the the term term “broadcasting” “broadcasting” was was in inagriculture. agriculture. LeavingLeaving Certificate Certificate Physics Physics (OL) (OL) 2002 2002 Q. Q.7 7 ManyMany crop crop plants plants are are sown sown in inrows rows or or drills drills to to facilitate facilitate harve harvesting.sting. LeavingLeaving Certificate Certificate Physics Physics (pp. (pp. 30-33) 30-33) sets”sets” were were commonly commonly used used to to pick pick up up the the transmissions. transmissions. Apart Apart from from TheThe following following table table gives gives examples examples of of electromagnetic electromagnetic waves waves and and However,However, grass grass seeds seeds are are generally generally scattered scattered more more widely widely and and • • Wave Wave phenomena: phenomena: reflection, reflection, refraction, refraction, diffraction, diffraction, interference, interference, headphonesheadphones these these devices devices typically typically had had just just three three components: components: theirtheir typical typical wavelengths. wavelengths. randomlyrandomly ― ― a apractice practice known known as as broadcasting. broadcasting. polarisation.polarisation. Everyday Everyday examples, examples, e.g. e.g. radio radio waves, waves, waves waves at at a acoil coil of of insulated insulated wire, wire, a acapacitor capacitor and and a acrystal crystal which which acted acted as as a a RecoveredRecovered audio audio signal signal • • TelephoneTelephone calls calls are are usually usually ‘one ‘one to to one’ one’ and and are are bidirectional. bidirectional. sea,sea, seismic seismic waves. waves. diode.diode. Find Find out out more more about about crystal crystal radios radios on on websites websites such such as: as: micro-micro- InIn contrast, contrast, radio radio and and TV TV broadcasting broadcasting is isa a‘one ‘one to to many’ many’ process process wavewave radioradio infraredinfrared light light ultraviolet ultraviolet • • Longitudinal Longitudinal and and transverse transverse waves: waves: frequency, frequency, amplitude, amplitude, https://en.wikipedia.org/wiki/Crystal_radiohttps://en.wikipedia.org/wiki/Crystal_radio wavewave andand is isunidirectional. unidirectional. TheThe coil coil + +capacitor capacitor (in (in parallel) parallel) acted acted as as a a‘tuned ‘tuned circuit’ circuit’ which which wavelength,wavelength, velocity. velocity. Relationship Relationship c c= =f λ.f λ. • • TheThe Athlone Athlone radio radio transmitter transmitter was was opened opened in in1932, 1932, broadcasting broadcasting wouldwould respond respond best best to to one one frequency. frequency. The The diode diode rectified rectified the the wavelengthwavelength 100100 m m 0.1 0.1 m m 1 1μm μm 600 600 nm nm 10 10 nm nm onon 567 567 kHz kHz (i.e. (i.e. in inthe the ‘medium ‘medium wave’ wave’ band). band). Its Its name name was was • • The The electromagnetic electromagnetic spectrum: spectrum: Relative Relative positions positions of of radiations radiations in in alternatingalternating radio radio frequency frequency oscillation oscillation which which could could then then be be termsterms of of wavelength wavelength and and frequency. frequency. • • Name Name one one property property that that all all of of these these waves waves have have in in common. common. changedchanged from from Radio Radio Athlone Athlone to to Radio Radio Éireann Éireann in in1937. 1937. It Itwas was ‘smoothed’‘smoothed’ slightly slightly by by a asecond second (small) (small) capacitor. capacitor. replacedreplaced by by the the Tullamore Tullamore transmitter transmitter in in1975. 1975. That That too too was was • • Polarisation Polarisation of of transverse transverse waves: waves: Demonstration Demonstration of of polarisation polarisation • • What What is isthe the frequency frequency of of the the radio radio waves? waves? switched-offswitched-off in in2008. 2008. The The only only remaining remaining AM AM broadcast broadcast by by RTÉ RTÉ (of(of light) light) using using polaroids polaroids or or other other suitable suitable method. method. AntennaAntenna • • Describe Describe how how infrared infrared radiation radiation can can be be detected. detected. (at(at least least until until 2017) 2017) is ison on 252 252 kHz kHz (longwave) (longwave) transmitting transmitting fro fromm ScienceScience and and Technology Technology in in Action Action is isalso also widely widely used used by by • • Give Give two two uses uses of of microwaves. microwaves. Clarkstown,Clarkstown, Co Co Meath. Meath. TransitionTransition Year Year classes. classes. TheThe speed speed of of light light is is3 3× ×10 108 m8 m s –1s.–1 (.c ( c= =fλ fλ) ) coilcoil headphonesheadphones LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2006 2006 Q. Q.12 12 b b BiographicalBiographical Notes Notes tuningtuning capacitor capacitor diodediode rectifier rectifier TheThe diagram diagram shows shows the the relative relative positions positions of of electromagnetic electromagnetic LearningLearning Outcomes Outcomes radiationsradiations in in terms terms of of their their wavelength. wavelength. ReginaldReginald Fessenden Fessenden 1866 1866 - 1932- 1932 MakeMake a aposter poster that that illustrates illustrates the the operation operation of of a acrystal crystal radio radio. . ReginaldReginald Fessenden Fessenden was was born born in inQuebec, Quebec, OnOn completion completion of of this this lesson, lesson, students students should should be be able able to: to: gammagamma micro-micro- NoteNote that that the the basic basic principles principles of of tuned tuned circuits circuits apply apply to to modern modern radio radio A A UVUV lightlight IR IR B B Canada,Canada, in in1866. 1866. At At the the age age of of fourteen fourteen he he raysrays waveswaves • • explain explain the the general general principles principles of of radio radio freqeuncy freqeuncy transmission transmission andand television television receivers, receivers, mobile mobile phones phones and and wifi wifi communication. communication. waswas employed employed as as a amathematics mathematics teacher teacher for for • • calculate calculate the the wavelength wavelength of of an an electomagnetic electomagnetic wave wave given given the the 2.2. On On the the following following website website there there is isa atable table of of radio radio transmitters transmitters in inthe the • • Name Name the the radiations radiations marked marked A Aand and B. B. thethe younger younger pupils pupils while while he he was was studying studying in in frequency,frequency, and and vice vice versa versa MunsterMunster area. area. The The power power of of some some transmitters transmitters is isover over 100,000 100,000 watts watts • • Give Give one one property property which which is iscommon common to to all all electromagnetic electromagnetic thethe University. University. • • explain explain what what is ismeant meant by by amplitude amplitude mudulation mudulation whilewhile others others are are around around 20 20 watts. watts. What What do do you you notice notice about about the the radiations.radiations. AtAt the the age age of of twenty twenty he he applied applied for for a ajob job with with • • outline outline the the advanages advanages and and disadvantages disadvantages of of using using higher higher radio radio locationlocation of of the the high high power power transmitters? transmitters? • • Which Which one one of of the the radiations radiations has has the the shortest shortest wavelength? wavelength? ThomasThomas Edison Edison and, and, though though he he was was turned turned down down frequencies.frequencies. http://homepage.eircom.net/~fm_radio/munsterFM.htmlhttp://homepage.eircom.net/~fm_radio/munsterFM.html • • Describe Describe how how IR IR radiation radiation is isdetected. detected. atat first first he he was was eventually eventually successful. successful. He He gained gained • • Give Give one one use use for for microwaves. microwaves. valuablevaluable practical practical experience experience there. there. When When he he was was 24 24 he he was was appo appointedinted professorprofessor of of Electrical Electrical Engineering Engineering at at Purdue Purdue University. University. True/FalseTrue/False Questions Questions LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2005 2005 Q. Q.6 6 InIn 1898-99 1898-99 he he successfully successfully developed developed a awireless wireless telephone telephone syste system.m. GeneralGeneral Learning Learning Points Points A Asatellite satellite transmits transmits radio radio signals signals to to earth. earth. At At a aparticular particular time time the the WhenWhen he he learned learned of of Marconi’s Marconi’s work work he he realised realised that that he he could could make make a a a)a) The The first first radio radio transmission transmission was was mademade in in 1875. 1875. T T F F satellitesatellite is is1.2 1.2 × ×10 1012 12m m from from Earth. Earth. How How long long does does it ittake take the the signal signal TheseThese are are additional additional relevant relevant points points which which are are toto travel travel to to earth? earth? It Itis isnoticed noticed that that the the frequency frequency of of the the re receivedceived radio radio muchmuch more more efficient efficient system. system. In In 1900 1900 he he began began work work for for the the US US WeatherWeather usedused to to extend extend knowledge knowledge and and facilitate facilitate discussion. discussion. b)b) Radio Radio wavelengths wavelengths are are typically typically less less than than 1 1mm. mm. T T F F signalsignal changes changes as as the the satellite satellite orbits orbits Saturn. Saturn. Explain Explain why. why. BureauBureau to to set set up up radio radio stations stations to to transmit transmit weather weather data. data. He He re receivedceived • • An An electric electric current current in in a aconductor conductor has has an an associated associated magnetic magnetic c)c) The The direction direction of of polarisation polarisation of of electromagnetic electromagnetic waves waves hundredshundreds of of patents patents for for his his inventions, inventions, including including the the continuou continuous waves wave (universal(universal gravitational gravitational constant constant = =6.7 6.7 × ×10 10–11–11 N Nm m2 kg2 kg–2;–2 ; field.field. WhenWhen the the current current stops stops the the magneticmagnetic field field disappears, disappears, is isthat that of of the the electric electric field. field. T T F F transmitter.transmitter. In In January January 1906 1906 he he succeeded succeeded in inmaking making the the first first two-way two-way massmass of of Saturn Saturn = =5.7 5.7 × ×10 1026 26kg; kg; speed speed of of light light = =3.0 3.0 × ×10 108 m8 m s –1s)–1) butbut the the effect effect takes takes time time to to propagate. propagate. d)d) A Aradio radio antenna antenna radiates radiates electric electric and and magnetic magnetic fields. fields. T T F F transatlantictransatlantic transmission transmission of of Morse Morse code. code. • • Opposite Opposite electric electric charges charges have have an an associated associated electric electric field. field. e)e) Radio Radio signals signals do do not not travel travel as as fast fast as as light. light. T T F F LeavingLeaving Certificate Certificate Physics Physics (HL) (HL) 2004 2004 Q. Q.5 (f)5 (f) • • If Ifan an alternating alternating potential potential is isapplied applied to to an an aerial aerial it itradiates radiates electromagneticelectromagnetic waves. waves. f) f) The The frequency frequency of of AM AM broadcasts broadcasts is isgenerally generally much much lower lower WhatWhat is ismeant meant by by polarisation polarisation of of waves? waves? thanthan fhe fhe frequencies frequencies used used for for FM. FM. T T F F • • The The first first radio radio transmitters transmitters were were used used to to send send messagesmessages ReviseRevise The The Terms Terms (telegrams)(telegrams) using using Morse Morse code. code. g)g) AM AM broadcasts broadcasts are are being being phased phased out out because because they they are are not not JuniorJunior Certificate Certificate Science Science (HL) (HL) 2005 2005 CanCan you you recall recall the the meaning meaning of of the the following following terms? terms? • • Radio Radio signals signals are are elctromagnetic elctromagnetic and and so so cannot cannot be be heard. heard. asas effective effective in in mountainous mountainous areas. areas. T T F F Q.Q. 1 1 RevisingRevising terminology terminology is isa apowerful powerful aid aid to to recall recall and and retention. retention. InIn order order to to transmit transmit speech speech or or music music the the radio radio signal signal is is h)h) The The wavelength wavelength of of a a1 1MHz MHz electromagnetic electromagnetic wave wave is is (j)(j) The The diagram diagram shows shows a acurrent current carrying carrying modulatedmodulated either either in in amplitude amplitude or or frequency. frequency. wirewire passing passing through through a acard. card. aerial,aerial, amplitude amplitude modulation, modulation, antenna, antenna, bandwidth, bandwidth, broadcasting, broadcasting, crystal crystal 300300 metres. metres. T T F F radio,radio, cube, cube, diffract, diffract, digital digital terrestrial, terrestrial, direct direct digital digital satellite, satellite, electric electric field, field, • • Satellites Satellites are are now now used used to to relay relay television, television, radio, radio, phone phone and and i) i) Digital Digital broadcasting broadcasting makes makes more more efficient efficient use use of ofthe the electromagneticelectromagnetic waves, waves, frequency frequency modulation, modulation, geostationary geostationary orbi orbits,ts, faxfax messages. messages. ShowShow a amagnetic magnetic field field line line on on the the availableavailable bandwidth. bandwidth. T T F F cardcard in in the the diagram diagram with with direction direction headphones,headphones, magnetic magnetic field, field, megahertz,megahertz, MorseMorse code, code, radio radio frequen frequency,cy, clearlyclearly indicated. indicated. CardCard television,television, vertically vertically polarised, polarised, wired wired telegraphy. telegraphy. CheckCheck your your answers answers to to these these questions questions on on www.sta.ie. www.sta.ie. CheckCheck the the Glossary Glossary of of terms terms for for this this lesson lesson on on www.sta.ie www.sta.ie