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there's something rather magical about radio waves they're actually a sort of invisible energy this aerial can actually pick up enough of this energy to power this primitive receiver I made it has no battery it relies entirely on harnessing the energy of the radio waves in the air it's not very loud so I have to put it straight on the microphone so you can hear it I managed to pick up radio Israel broadcasting from Jerusalem on it one night although there's something quite wonderful about this little thing radio sets have been around for so long now that they've become rather ordinary unglamorous contraptions and even the electronics inside now look rather familiar in this program I'm going to look at how these mysterious radio waves were discovered and how radio receivers managed to pick them up creating radio waves is actually very simple any electric spark emits them each of these sparks is sending out radio waves you hear them on the radio as interference that's why lightning makes radios crackle and even the tiny spark inside a light switch is enough to produce a little pulp but without a radio set though it's not easy to detect these waves and most scientists didn't believe they existed till just over 100 years ago what finally convinced them was an experiment performed by the physicist Heinrich Hertz in 1887 it was first demonstrated in Britain by a scientist called Oliver Lodge here in the Royal Institution Hertz used very big sparks created by a machine like this called an induction coil you turn it on boom this was connected to these metal plates with another spark gap in the middle and this acted as a sort of aerial this was Hertz his receiver it's simply a loop of copper wire well the big spark creates radio waves with enough energy to make a tiny spark jump across the gap between these balls in the receiver when they're held very close together so hold them in position okay bill if you look carefully you can just see the spark jumping across the gap these sparks are so tiny that hertz had to let his eyes get accustomed to the dark for 15 minutes and then watched the sparks through a magnifying glass his apparatus only had a range of a few meters and he had no interest in finding any practical uses for it the first person to use radio waves for signaling was Giulio Moammar Coney Marconi had been a difficult child his mother was a Jameson from the Irish whiskey distillers who'd run away to Italy to be an opera singer and married an Italian landowner she quickly got bored on his estate it's not what's going on here I think we'll go for a little jaunt Infant Marconi spent much of his childhood being dragged around Europe by his mother Barcelona or perhaps Bologna shows little interest at school and constantly irritated his father with ridiculous scientific experiments blood let's measure your visa shortly after failing to get into university he happened to read an article about Hertz his work oh he immediately started obsessively experimenting it soon managed to transmit the signals over a mile sil aged only 20 he arrived in England try and sell his ideas Marconi had found that fixing one side of the spark gap to a long vertical wire made a much better aerial than Hertz's this was further improved by connecting the other side of the spark gap to earth apart from that the transmitter was basically the same as Hertz's any electrical spark will do here it's being provided by the ignition circuit of Rex's pickup truck this primitive transmitter has a surprisingly long range Marconi also used the much more sensitive receiver called cojiro this is based on a design by Oliver Lodge this is my homemade version is just a tube of nickel filings I made it by filing down a coin you fix one end to the aerial another kite and the other end to the earth and what happens is that when it detects the radio waves its electrical resistance Falls dramatically so it acts as a sort of switch and turns on a circuit the theory behind it is very complicated and wasn't worked out for till many years later but it's quite simple to make it work the only slightly complicated thing is that you have to have something to shake it to restore its high resistance at the end of each signal so now if I signal to Rex this is Marconi's original equipment that he brought to England with him this is his transmitter with an induction coil like Hertz's and these balls that concentrated the energy of the spark one end would have been connected to the aerial this is his receiver the aerial went on here this is his coherer inside the glass tube the filings are actually in the gap in the middle and this is the device to tap it Marconi would have been sending a combination of long pulses and short pulses sending messages in Morse code well this original operators only had a range of about three miles but Marconi gradually increased the sensitivity of his coherence and the size of his transmitters till he was sending messages hundreds of miles the larger transmitters had much larger spark gaps which got very noisy so he had to take to putting them in enclosed boxes Marconi's early systems had a big disadvantage they couldn't be tuned you can hear the signal from our spark transmitter all across the short medium and long wave bands the reason is that sparks create chaotic waves and all sorts of different wavelengths what was needed was a more precise transmitter than a spark this was the solution the tuned circuit it suddenly all starts to look like a proper radio but the basic parts are still quite simple as a coil of wire here called an inductor and a series of overlapping metal plates here called a capacitor the electricity whizzes backwards and forwards from one to the other oscillating thousands of times a second the valve acts as a sort of pump keeping the whole thing going you can see a picture of the radio waves this tuned circuits transmitting on this oscilloscope that I've hooked up to a short aerial if I hold it near the tuned circuit and switch on you can see how regular the oscillations or waves that it's transmitting are now if I compare this with this spark machine you can see just how chaotic its radio waves are once the tuned transmitter had been perfected spark transmitters were quickly banned for polluting the airwaves with the problem of interference solved radio seems so miraculous that it could be capable of almost anything early radios did still have one limitation they couldn't transmit speech only the simple pulses of Morse code Morse code still used for messages on the shortwave band and pulse codes are also used in radio-controlled models I built this little car for a children's television series and I've hooked up the oscilloscope to the transmitter so you actually see the stream of pulses that the car receives if I work this switch that's the one works their headlights you can see it just moves one pulse if I shift that one works two pulses which actually opens the door this one works a steering from left to right you see it's moving four pulses this one is shifting five pulses and that's the speed control for forwards and backwards control and so forth each each series of pulses work a different function inside the car to transmit speech and music instead of simple pulses you first have to convert the sound to electrical signal with a microphone and then combine it with the radio waves in the radio receiver it all gets separated out again you can see this very clearly on an oscilloscope if I turn on this little radio and I now plug the oscilloscope in to the loudspeaker it's a bit bit large this is giving a picture of the sound signal and you can see it roughly matches the sound that's coming out of the loudspeaker now if I plug it in further back on the circuit this is the sound signal combined with the radio waves you can see the peaks Hill roughly match the sound that is making and the radio waves are actually going rapidly up and down in the middle now if I stretch this out of it these are the actual radio waves and you can see what's happening is that the sound is constantly changing their size or their amplitude that's why this is called amplitude modulation or AM radio the man who designed much of the practical circuitry for AM radio was an American called Edwin Howard Armstrong while in France during World War one he invented the super head circuit which has been used ever since he then sold a patent to RCA back in America I have an appointment to see mr. Sun office Ernest expecting you sir Armstrong thanks you're welcome he became a millionaire overnight and fell in love with the Chairman's secretary how about you come for spinning my motor okay hop in there oh it sure is a big one he bought a huge hispano-suiza and climbed his tallest aerial to impress up they were married soon afterwards will you marry me Oh Howard my hero the fundamental principles of radio have remained unchanged this is the BBC transmitter at Brockman's Park broadcasting medium wave radio to southeast England inside the engineers have restored the BBC's very first transmitter built by the Marconi company in about 1920 this end of it actually creates the radio waves and this end of it combines them with the sound signal the amplitude modulation it's basically a series of giant tuned circuits with the valves the coils of wire of the inductors and the overlapping metal plates of the capacitors well this generates about two kilowatts this may sound a lot but some this modern transmitter is rated 150 kilowatts and it's all much more sophisticated this one's actually broadcasting Radio 3 on am all over southeast England inside though the basic components are still remarkably similar the inductors have remained exactly the same and the vowels and capacitors although they're now more enclosed still work on the same principles as well transmitters like these broadcasting sound first appeared in World War one they were used for sending messages by radio telephony broadcasting radio to entertain people was first started after the war by enthusiastic Marconi engineers the BBC was then set up by the government in 1922 and listening to the radio rapidly became very popular at first most listeners had very simple receivers crystal sets like the Rexha phone they needed enormous aerials because like my radio at the start of the program they had no battery and relied entirely on the energy of the radio waves in the air it's easier to see how they worked on this homemade version instead of a cojiro it has a lump of crystal and a fine wire called cat's whisker electricity will only flow one way through the contact between the wire and crystal and this has the effect of separating out the sound from the radio waves like the coherer the theory behind the cat's whisker is very complicated but it's quite simple to make it work the imperfect contact between teeth and fillings can occasionally have the same effect causing a few unfortunate people to hear the radio inside their head all the time this is the modern equivalent of the cat whisker the germanium diode I put under a magnifying glass you can see it's an enclosed version of the same thing you can see the whisker just touching the lump of germanium the primitive radio I had at the beginning of the program work with one of these and in fact most modern transistor radios still use them as well much of the radio sets evolution has been preserved by Gerald wells of the vintage wireless museum if you wanted something better than a crystal set what sort of thing would you had well you could have had something like this which is three separate units hence it was called a wireless or radio set but it was a set of parts would have consisted for tuned circuit an RF amplifier a detector stage and a power output stage and that would have got you most of local stations where your phones or sma'da stood out speaker what happened after that was the next stage well the next stage they decided to stick it all in one box to make it less wise and make it neater and this was a bit more elaborate as well more stations were coming the airwaves so more elaborate tuning was needed so we bought in series parallel switching for aerials and tuned circuits variable condense and reaction condenser an RS stage to amplify the signal detect a stage to take the place three old-fashioned cat's whisker and two stages of LF amplification that would be quite an elaborate set but you could by moving these bars around do away those stages and listen with earphones on there and save a lot of battery power when they start in closing or all they working parts of the radios well certainly by the mid twenties when they decided this wasn't really very nice of a living room and so we started building it'ld familiar objects like a medicine chest for instance where it could be easily disguised and met wouldn't disgrace any respectable home what are the shape well the most famous of all of course is the smokers cabinet every home had a smokers cabinet you'd have a your pipe racks and a bits of a top it was smoking as big industry you'd have you draw at the bottom where you'd have your pipe cleaners your matches new tobacco and it all fold away and look quite innocent it didn't scream while this area because all these early radios were powered by batteries weren't they well yes there was very little electricity around and the early radios required a 2 volt accumulator sometimes 4 or 6 usually 2 which had to be charged up every week's let me - had two of them one being charged one in use and you'd need a high-tension battery you need a grid bias battery the good bias battery lasted about a year and cost 9 pence that would last about three months and cost you seven six months so a little quite expensive and it was an expensive business and it took a lot of rigging up had happen elaborate here is a nerve system and all the bother of getting accumulated charged every week admitted it was only from us reasonably cheap but it did mean we had to be careful you had about 20 hours listening a week so but when you went to your radio shop there was usually a Radio Times provided on the counter that saved you buying one movie a diverse bakelite sounds and pen and a pad you could make notes of what was worth listening to during the following week they fit your programs and plan your meals around the wireless set you didn't just hear it you actually sat down and listened to it and gave it all your attention you had to it'll cost you so much to read up and of course when you came in with your accumulator every week it was all the other older tablets and red bags in there changing the accumulators as well and you would discuss the programs so the reputation of wireless programs was made and lost in a wireless shop by the 30s the appearance of radios had started to change dramatically with the introduction of the new material bakelite pioneered in Britain by the echo company this could be molded to almost any shape it's one drawback was that it was easily breakable see these two portable radios well watch this letter go Betsy sorry friend you old-style portables have to go but look at our new RCA Victor portable radio came through without a chip RCA Victor's non-breakable impact case means no chipping no cranky no braking and hear that tone its RCA Victor's great golden throat sound see the world's only portables with a non-breakable impact case as low as 27 95 your RCA Victor dealer the biggest change in broadcast radio since the war has been the introduction of FM the great advantage is that it's much less susceptible to interference de-spawn which drowns out I am hardly audible on FM so why should use the phrase guerrilla warfare because there are FM stands the frequency modulation the principle behind it's really quite simple instead of the sound altering the amplitude of the radio waves as in a.m. it alters their frequency FM radio was yet another invention of Howard Armstrong he started working the early 30s with a missionary zeal to produce true high fire rate after encouraging tests with RCA the company suddenly pulled out Sarnoff well why have you cancelled my project I get off my back every always happen when it's a TV when FM radio is becoming established Armstrong an RCA started a lengthy battle over the papers I was in a bedroom certainly not this had a disastrous effect on his health and on his marriage ah that does a terrible day by the way I'm leaving last straw I can't take any more FM has now become firmly established and is invaluable for radio communications as well as for broadcasting when I fly my little aircraft I use radio I firstly wouldn't fly without one this enables need to keep in touch with air traffic control and other air users and also airfields and tell them of your intentions and if you do happen to get lost air traffic control can help you find your way and it also is a navigational radio I can tune in to various fixed beacons throughout the country I can fly directly to and from these beacons and that helps immensely to find your way around the country domestic radios have also become much more sophisticated many now have automatic push-button tuning and the sound quality can be very impressive particularly in stereo FM but despite this improvement radio has really been eclipsed by television and other modern marvels and radio sets aren't the important prize possessions they once were in fact the whole idea of a separate radio set is rather disappearing radios now tend to be combined with the cassette tape recorders or alarm clocks or hi-fi systems radio is so taken for granted today it's hard to think it is magical anymore but I hope in this programme I've managed to persuade you that it still is you