Bouncing Around The World - EWTS #018

Joe: Hello and welcome to Enough with the Science. I’m Joe.

Senan: And I am Senan. How are you Joe this week?

Joe: Very good. Absolutely. And if it’s your first time along to our little podcast, you’re in for a very special treat. This is a two-parter but basically what we do here is Senan researches a topic of interest to his giant brain and tries to explain it to me.

Senan: Don’t mind him. I don’t research it; I know it already.

Joe: We’re going to test you because I’ve got questions now. And today’s topic is so epic that it’s actually going to be a double episoder.

Senan: It’s another double header. Despite our best efforts to fit things into 30 minutes we just can’t manage to do it.

Joe: Well we can. The first part of this is going to be inside 30 minutes. That’s our promise today.

Senan: A promise which I assure you will be broken. [laughter] So anyway Joe, tell me, are you like me; do you spend far too much time with your head stuck in your phone?

Joe: I’ve tried. I’ve got better, but yes. I mean there’s no right amount of time to be at your phone really. There’s zero time.

Senan: We have this fabulous amazing device in our pocket and we use it to watch pictures of cats riding around on robot lawnmowers.

Joe: Yes you do. Yes you do.

Senan: And we completely forget that the slab of glass and plastic that’s sitting in our pocket all day long, has the most amazing collection of radio technology in it.

Joe: We take it for granted. I remember Louis C.K. talking about how you can get so frustrated when you’re trying to download something and it takes longer than two seconds. And he’s like; “Can you give it a minute? It’s bouncing off a satellite in space. It’s coming from space. Can you just give it a second.”

Senan: That’s it like. We have this thing; there is 170 years of absolutely amazing scientific innovation has gone into producing that thing that’s in your pocket that you take for granted that gives you perfect quality phone calls, perfect internet, video calls with your grandma, GPS, you name it. It’s all in there.

Joe: It’s amazing though in two ways. Like it’s 170 years of effort and hard work and sweat and tears by so many people. But also it’s only been 170 years since we lived in a world where there was no sound other than shouting over there.

Senan: Yeah. And considering we have just spent two minutes waffling about nothing I feel we’ll definitely go over the 30 minute mark this week.

Joe: Well we waffle about nothing. Like this is another 28 minutes of waffling about nothing.

Senan: So anyway yes, the subject of this podcast and indeed the next episode is the whole evolution of radio. That whole 170 years of scientific development that has culminated in that amazing thing that you carry in your pocket.

Joe: I think because I did really; that you forget that it is radio that drives your mobile phone. It’s not; it should be nearly called a mobile radiophone but…

Senan: Yeah. There was a time when we called them walkie-talkies before they got complicated.

Joe: Yeah. But then you could only talk to one person. Wasn’t a happier time.

Senan: So anyway, it all started 170 years ago. We didn’t know; we the human race did not know that radio waves existed. We had no clue that this invisible thing that you can’t smell, see or touch actually is all around us all the time. And I guess the beginning of the story is round about 1850 with a French chap called Léon Foucault. Obviously we knew…

Joe: Were you pronouncing that right?

Senan: No. Absolutely not. And I’m not going to make another attempt at it. [laughter] Anyway. Obviously we knew light existed because we happen to have receivers for light built into the front of our face.

Joe: Right. Eyes.

Senan: Eyes. And this enterprising chap decided; I wonder how fast does light travel? Well he kind of; some other people had made an attempt to measure the speed of light so he knew it did travel at a certain speed but he reckoned he could do a better job of measuring the speed of light. And he came up with this complicated contraption made of kind of spinning mirrors that were spinning really fast. Without getting too bogged down in the detail he managed to work out…

Joe: Can you just; can you just hold on to that idea? Don’t get too bogged down in the detail. That’s the name of this podcast. Don’t get bogged down in the detail.

Senan: That’s this week’s episode folks. See you the next time. [laughter]

Joe: He calculated the speed of light and now we have mobile phones. Goodbye.

Senan: Anyway yeah, he did. The point is this bloke did an amazing job with very rudimentary equipment. He got the number almost right. He got very close to the real number that we now know because we have modern equipment. So that was fine; that was 1850. Let’s go forward ten years. A Scottish gentleman called James Clerk Maxwell. Now this guy; he was a theory guy right? And a mathematician. So he was pencil and paper and slide rules and that was about it; he didn’t really do much by way of experiments. And he wasn’t really interested in light. What he was interested in was electricity and magnetism. You know; people were aware by then that magnetism; they had magnets. They knew magnetism existed and they had simple electrical devices so they kind of knew electricity existed. And they knew there was like a field created; certainly with magnetism you could see it because one magnet pulled another one towards it. But also they kind of had seen effects caused by electrical currents that there was a field of some kind around an electrical wire. And this guy wanted to figure out what the relationship between them was. And he was doing; remember we’re talking about mathematics now; pencil and paper, that’s all. So he got going on his equations and he figured out that there was a kind of a self-sustaining dance going on between electricity and magnetism. So a magnetic field would create an electric field and that electric field would create a magnetic field. So this self-propagating dance would go on. And he figured out that well that must create waves of electricity and magnetism travelling through space. That was his; that was kind of his theory.

Joe: Right. Now I am lost already but I don’t think we need to understand this.

Senan: Well we did an episode; oh god it must be last year now; all about the electromagnetic spectrum.

Joe: Oh I know. I remember the EM spectrum but this little dance between electricity and magnetism creating waves…

Senan: Well we did talk about it then. But anyway yeah. Anyway so…

Joe: I should go back and listen to that.

Senan: You’ve got this pair of waves travelling through space and they’re kind of sustaining each other. He then went a bit further with his mathematics and he figured out how fast they travel through space. And discovered it was a constant speed. No matter what size the waves were; the actual speed that they travel through space was constant.

Joe: In theory.

Senan: And then; no in practice. Oh well yeah it hadn’t been tested. And then somebody brought the French gentleman’s measurements to his attention and he discovered that the number he had came up with matched the speed of light measurement your man with all the mirrors and things had done ten years earlier. And he said well the obvious connection here is that light is obviously some form of electromagnetic radiation. If it travels at the same speed as other electromagnetic radiation…

Joe: If it walks like a duck…

Senan: Yes exactly. It quacks. So he played around with his equations some more and he figured out that well; in theory there’s no reason why we can’t have much longer wavelengths; much higher frequencies or much lower wavelengths… you know; much shorter frequencies and so on.

Joe: So at this stage he didn’t actually know what the frequencies were?

Senan: Well his mathematics told him that the waves would travel at a certain frequency. In other words that electromagnetic waves would travel…

Joe: Okay.

Senan: You know that the wave would rise and fall in a certain sequence; in a certain time pattern.

Joe: Yes.

Senan: Right; which we now call frequency. Which is how often; if you’re standing in one spot it’s how many waves pass you in a second.

Joe: But he didn’t know the difference between magnetism and electricity and light?

Senan: Well he made the intuitive leap that if light travelled at the same speed as his equations for electromagnetic waves; light must be an electromagnetic wave.

Joe: But it must have the same frequency?

Senan: Well no. I mean he knew there was going to be different frequencies. But his intuition then was when he followed up the mathematics a bit further was that; you weren’t restricted to the particular frequencies that light was at.

Joe: Right.

Senan: There could be all these other frequencies. So essentially he came up with the idea that there was all these other types of electromagnetic radiation which you couldn’t see. We could see light but there must be all these other ones because his maths said there must be. But we can’t see them.

Joe: Right. So there’s invisible EM waves.

Senan: Yeah. And the terrible tragedy right was; he died before anybody proved it. And he was right.

Joe: So he died without knowing he was right.

Senan: He died without being sure by; there was no experiment that proved…

Joe: It’s a little bit like being married. [laughter]

Senan: I'd really like you to develop that thought out a bit further. Please.

Joe: He died without knowing he was ever right.

Senan: And Joe’s wife; I am going to make sure you listen to this episode. [laughter]

Joe: This will be our last podcast. Well it’ll be my last podcast.

Senan: Right. We’re going to move forward about 25 years to 1887. And a gentleman that most of us have heard of, Mr. Hertz. Heinrich Hertz; a German physicist. Now he was not the father of rental cars. However he is the man who we now name our measurement of frequency after. So anybody who’s ever used a radio knows that you’ve got megahertz and kilohertz et cetera. Well one hertz is one cycle per second. In other words one wave per second passing by you.

Joe: Right.

Senan: And one kilohertz is a thousand of them per second and one megahertz is a million of them per second. This is the guy who basically proved that radio waves are a real thing. So he built a simple apparatus. Basically two metal rods. Tiny gap; they were kind of in a frame and it held them in a place where there was like a tiny gap between the end of the two rods. And the other ends of the rods were connected to a powerful electrical generator. Right?

Senan: This fellow was going to set his house on fire.

Joe: I just love these experimental guys. It’s kind of; "I’m just downstairs hun, don’t you worry. This is what I’m at."

Senan: Yeah. "Ignore the noises you’re about to hear."

Senan: And at the other end of the room he had a simple circular wire loop.

Joe: Right.

Senan: Was not connected to anything. It was a complete circle except for one tiny gap at one side of it. So it was a circle with a very narrow gap in it. He turned on his generator and he observed that a spark jumped in the metal rods that were connected to the generator. In the small gap between the ends of the rods a spark jumped. And then when he looked at the other end of the room; a spark jumped in the gap in the circle that wasn’t connected to anything. So that was how he proved that something travelled through the air. Effectively the spark between the two metal rods in his transmitter generated a burst of radio waves and the loop of metal at the other end of the room picked up some of those radio waves; converted them back into electricity and created a spark in the gap.

Joe: He must have gone loopers when that happened.

Senan: Yeah. I’d say he might have gone for a pint that night.

Senan: Either that or somebody locked him up. How was he looking at both of them at the same time? Like the spark…

Joe: Well maybe he had an assistant. You never know. It’s always the case; the assistant never gets seen again.

Senan: We probably should be measuring radio waves with Frankenhofen or something.

Joe: Yes. So Hertz was the assistant. Imagine if that was the case.

Senan: The really; maybe he was. Could be right yeah. He probably said to his boss; "Hold this for a minute would you?" [laughter] Anyway. The really ironic thing about it all was when he was finished this set of experiments he formed the conclusion; "This radio thing; we know it exists but it’s completely useless."

Joe: It’ll never catch on.

Senan: "It’ll never catch on," he said to himself and everybody else that would listen. So not long afterwards another bloke; a French man again called Édouard Branly heard about Hertz’s experiments and he wondered if maybe we could make a more reliable way of receiving it. So I’m not sure how he arrived at this thought process but he ended up…

Joe: I think after a long time would be my thought on it.

Senan: It wasn’t very long after Hertz actually. Maybe he was Hertz’s assistant. I don't know.

Joe: Where? Where are we now time wise? We’re 18-what-ish?

Senan: So we’re still like maybe towards the very end of the 1880s.

Joe: Right. Okay still a very short time since…

Senan: Yeah yeah. So Hertz was 1887 so like maybe a year or two later. Anyway. This guy he came up with this glass tube with a bunch of metal filings; like iron filings inside in the tube. And the ends of it were sealed except that there was a metal probe coming in either end into the tube but they didn’t meet in the middle right? Outside where those metal probes were at the ends of the tube was wires connected to a battery and a light or a bell or something. Anyway it was a simple electric circuit. The metal tube acted as a switch to switch on or off the current in the circuit. Right?

Joe: Right.

Senan: So while the iron filings were sitting there in the bottom of the glass tube the switch was off. Electrical current couldn’t flow through the tube right because the iron filings weren’t making a circuit.

Joe: You would be delighted to know that I am following this.

Joe: Okay yeah got it. Iron filings not moving.

Senan: So he exposed this tube to a burst of radio energy from a spark gap transmitter like the one that Mr. Hertz had used.

Joe: Maybe the actual one.

Senan: Maybe the actual one; one never knows. And suddenly all the metal filings clumped together.

Joe: Yeah.

Senan: And they formed a circuit. They made a connection between one end of the tube and the other and hey; the switch was now suddenly on and the light or whatever the hell was connected to the battery came on.

Joe: Yes.

Senan: And then he turned off his radio transmitter and he tapped the tube with his thumb and the filings fell back to where they were and the switch went off.

Joe: So essentially he had discovered that he could build a big antenna and turn the light switch on in his house.

Senan: Yes. A remote control for his lights.

Joe: Lights. Very good.

Senan: But yeah; so it was the first hint of a practical use for radio. That you could make a switch that you could turn on and off remotely. And if you could do that you could maybe turn on and off your transmitter in a certain pattern that would send a code. You know; so that would cause the… this thing was called; this tube of metal filings was called a coherer because it kind of made a coherent clump of iron filings.

Joe: Right.

Senan: So your coherer could turn on and off a light based on the radio signals you were sending to it; maybe the pattern that light would allow you to send a message.

Joe: Morse code.

Senan: Morse code yeah. Yeah. Although I don’t know if Morse had actually been invented by then. Anyway. The next gentleman in the story is somebody we all know about and he did one particularly amazing thing which guaranteed that his name went down in history whenever anybody mentions the history of radio. And that is the Italian…

Joe: He invented it.

Senan: No no no. Well I think we can probably say that Hertz or Maxwell invented it but… The Italian Guglielmo… I’m making a mess of his Christian name but his surname was Marconi.

Joe: That’s almost; that; you sound like somebody from Napoli. [laughter] Napoli.

Senan: Anyway Marconi. A young Italian experimenter. Now the interesting thing about Marconi is he didn’t really have the patience for theory. He was a hands-on tinkerer. Like he liked to experiment with stuff and he was very persistent in his experiments. So he would try one thing; didn’t really work; we’ll change something we’ll try it again. And he just kept doing that over and over and over again. So he really wanted to try and find by trial and error; find ways. And one of his first really important discoveries was the idea of a radio antenna. In other words an efficient piece of wire or metal pole that would correctly or efficiently transmit your radio signal. And what he did was he connected long wires to like a tall tree or something so that they were going up into the sky. And he found that yeah that did a reasonable job of sending a radio signal a bit further away. But his big innovation was when he stuck the other end of the wire into the ground. Suddenly the signal went much further.

Joe: Right.

Senan: And it established the principle…

Joe: I can understand the tree thing right; that it’s kind of avoiding low-lying obstacles or ground-based obstacles. But why does sticking it into the ground; what does sticking it into the ground do?

Senan: Yeah so it’s to do with kind of a reflection effect. So the ground kind of reflects the radio waves a bit and it enhances the transmission by doing that.

Joe: Right.

Senan: And it’s still like today; grounding a radio antenna is still an important aspect of radio transmission. He was the first guy that started thinking about antennas and making antennas that would be more efficient and make your signal go further.

Joe: Yeah.

Senan: And he; over the course of a very short number of years he had some very good success. So 1896 he managed to send a signal a few kilometres; which doesn’t sound like a lot by modern day standards but nobody had done it before then.

Joe: Well considering we didn’t know it existed 26 years before that. It was essentially…

Senan: Yeah well maybe 50 years before it anyway. But yeah yeah. 1899 only three years later he sent a signal across the English Channel from England to France. So that was like maybe 20 or 25 kilometres something like that. But the real thing; the thing everybody remembers him for is in 1901; two years after the English Channel thing he sent a signal three and a half thousand kilometres from England to Canada. Across the Atlantic Ocean. That was a shocking thing at the time.

Joe: Yeah.

Senan: Like anybody who kind of had a bit of an understanding of what radio waves were all about; which wasn’t very many people back then; they were shocked because it didn’t make sense to them.

Joe: I have a question.

Senan: Yeah.

Joe: So this is the fastest way information is travelling at the time right?

Senan: Yeah.

Joe: He is in England. The buddies are in Canada with the… He sends the signal. How do they let him know that they’ve got it? Do they send him a letter? And like okay…

Senan: Maybe they put up a flare.

Joe: Maybe yeah. Did he send it; like three weeks later he gets a letter going; "Yes I got that." Well okay obviously they go; "Right exactly this time on this date." But he has to sit at home and wait.

Senan: Yeah.

Joe: For that information to go back.

Senan: The message they probably sent was sent back to him was; "Do you want vinegar on those chips?" [laughter]

Joe: Do you want… yeah. But I mean okay I can understand if it actually worked they could actually let him know. But what if it didn’t work? How’s he going to know? He’s going to sit there go; "Now maybe they’re sending a message."

Senan: Well now you see maybe he sent them a letter beforehand. Well I assume he had to go to Canada to set up a receiving apparatus.

Joe: Right.

Senan: So he probably told the guys in Canada; "At about this time I’m going to try and send you a signal."

Joe: Yes. But then they’re going to write a letter back to him. Like someone has to travel back with the information.

Senan: So unless they had a transmitter at both sides I don’t know if it was bidirectional; I don’t think so.

Joe: Yeah. He would have to wait.

Senan: He would have had to wait a couple of weeks to get the answer yeah yeah.

Joe: It’s not like; "Hello I’m in the other room." No.

Senan: It was a different world then.

Joe: Wow. Patience. Imagine pacing up and down you’re kind of going; "I wonder did it go. I wonder did it go."

Senan: Now the reason why people were shocked about that was; at this stage it was fairly well established that radio waves were the same stuff that light was made of.

Joe: Now when you say people then you obviously mean scientists.

Senan: Yes I mean sciency people. The kind of person that would be listening to this podcast.

Joe: Yes. Not your average man on the street kind of going; "Did you know light waves…"

Senan: So one of the reasons we know light travels in straight lines is because shadows appear on the ground.

Joe: Right.

Senan: Because you know some of the light is getting blocked by an object and the other light that isn’t getting blocked doesn’t bend around to fill the shadow.

Joe: Okay right.

Senan: And clearly you can do other things like shine a torch and you can obviously see on a foggy day that the beam is going in a straight line. Whatever. You get the idea. We know for sure light goes in straight lines. So because people knew that like light was an electromagnetic wave now; then they assumed all other electromagnetic waves must go in straight lines as well. You've got to remember the earth is curved.

Joe: You do got to remember that.

Senan: You do got to. And even if you say go to put a mountain that’s like 500 metres high; which is not a very high mountain but it’s the kind of ones we have here in Ireland; and you put a transmitter on top of that. The furthest in a straight line that you can hope to send a signal to somewhere else on the earth is like maybe 200 kilometres; something like that. At that stage the earth is curving away from the straight line of the signal and the signal just goes off, should go off into space.

Joe: Right.

Senan: So the idea that somehow a signal had not only gone past 200 kilometres but had gone to three and a half thousand kilometres was mind-boggling. How in God’s name did this thing bend around the curvature of the earth? So that was really the shocking thing about it. And it was only in 1901 that we found out for sure. I mean Marconi realised yeah well it works so he didn’t care too much about the theory.

Joe: So he didn’t care; he didn’t have any idea how it worked he just cared that it worked.

Senan: He might have had some ideas but he certainly had no certainty.

Joe: Yeah.

Senan: But he kept on; like he didn’t give up his experiments at that point. He said; "Right, I can make money out of this."

Joe: Yes. Somebody must have been financing him. I imagine or was he independently wealthy?

Senan: I don’t know what his circumstances were yeah. But I mean the Marconi Radio Company became a big thing.

Joe: Yes yeah.

Senan: So anyway a few years later 1901 these guys; Heaviside and Kennelly; they figured out that there was like an electrically charged layer high up in the atmosphere called the ionosphere. It’s essentially caused by solar radiation; radiation from the sun hitting the molecules up there.

Joe: Also in another Enough with the Science episode if you want to go back and have a listen to that one; we did the atmosphere.

Senan: Yes we did that one. So essentially they we won’t bother too much about the mechanism but they create a charged layer; the molecules at that level form a charged layer. And actually there’s several different layers at different levels but they’re all part of what we call the ionosphere. The key thing is they act like a mirror for radio. But they only act like a mirror; it’s a real fickle thing. They only act like a mirror for certain frequencies. So probably Marconi’s transmitter wasn’t all that efficient about using one frequency; it probably sent a burst of different frequencies. Some of them certainly did go off into space. But the right ones; the ones that are capable of bouncing off the ionosphere; they bounced off the ionosphere, they came back down, they bounced off the sea and they might have done that ten times before they got to Canada. Like it was pretty amazing when you can visualize it; these things bouncing around.

Joe: Yeah. You do think that radio waves just go zip. From one…

Senan: Yeah yeah. And it’s a real; that whole bouncing off the ionosphere is a real fickle thing. Like it’s still used today by certainly ham radio enthusiasts; amateur radio enthusiasts they use it to speak to people that are thousands of miles away using relatively low power transmitters. But also aircraft use it for their backup communications when their main system through satellites isn’t working. And the military use it; boats, ships use it et cetera. But the thing about it is that some frequencies; the really high ones don’t bounce at all. Then the mid ones; some of them might bounce during the day; other ones might bounce during the night. Some of the low ones might bounce lower and do really well. So there’s a whole pile of different rules. And then also the solar weather matters. So sometimes the solar activity is stronger than others and that affects which frequencies will work and which ones won’t. So it’s a real fickle thing. And the early radio operators that were using these rudimentary radio sets on ships; they had to understand all that and make sure they were using the right frequency at the right time.

Joe: Right.

Senan: So it was a bit of a black art back then. And the other thing about it is occasionally you get what’s called solar flares where there’s a big burst of radiation from the sun comes towards us. In some cases that just completely wiped out all radio long range radio transmission. And in other cases it enhanced it. So it was a real real fickle thing. So yeah that was the basics of how long range radio communication came to be. And then antennas of course as I mentioned with Marconi became a the whole science around antennas became important because the more efficient you could make your antenna; you your signal went further with less power. And you were also able to; if you had a better receiving antenna you were able to receive weak signals and hear them.

Joe: Right. So initially he’s just tying a wire to a tree.

Senan: Yeah and that was the basic straight pole antenna. And still in widespread use today; it’s simple; requires very little infrastructure; you just stick a pole or a wire up high in the sky and it works reasonably well. You know it’s not the most sensitive antenna; it spreads your signal out in absolutely every direction even though you might only want it to go east. But it works for most cases. There’s lots of different antenna designs and I’m no way I’m going to go through all of them but just…

Joe: No do; go on.

Senan: Some of the really important ones; thing called a Yagi. Now that sounds very exotic. We’ve all seen Yagis because they’re on the top of people’s houses; they’re used to receive TV.

Joe: Yeah.

Senan: They’re those that thing that looks like a fishbone. You know with all the little bits sticking out at the side and stuff. Essentially the difference is that that’s a directional antenna. It’s able to either send or receive a signal from a particular direction unlike the pole which sends it every direction. And then an even more refined version of that is a parabolic dish which again we’re all familiar with because it’s basically satellite dish.

Joe: Yes.

Senan: So we see satellite dishes on the sides of people’s houses for TV. That is a parabolic dish and that focuses the signal even more. So if you’re transmitting with one of them you can send a tight beam; you can use less power to reach further.

Joe: Right.

Senan: If you are receiving with one of them you can pick up a really weak signal and focus it in on for you know…

Joe: So basically like the dish bit reflects the stuff back into the…

Senan: Yeah. So in front of the dish about maybe you know 20 centimetres in front of the dish there is like this small little receiver unit. And the dish; the curve of the dish is very carefully set so that it reflects all signals down to that point where the receiver is.

Joe: Right. Yeah.

Senan: And then a modern development which our mobile phones make extensive use on of and in fact nearly all modern radios use to some extent are what’s called phased arrays. So this is like a grid of tiny little antennas on a circuit board. So you were no longer talking about a long wire or an antenna that looks long and thin. We’re talking about a pile of little bumps on a circuit board arranged in a grid and the electronics that control them are able to slightly tweak the timing… so the signal is sent to all of them but at slightly different times. And basically you can steer the signal using a phased array antenna. So…

Joe: And this is in your phone?

Senan: This is in your phone or in your Wi-Fi devices or whatever.

Joe: So you have a little tiny array of antennas.

Senan: Yes yeah yeah. And by varying; the electronics by varying the timing of how it interacts with those is able to steer the beam and focus on a particular direction.

Joe: Okay.

Senan: Yeah so that’s kind of antenna science has really gotten complicated you know.

Joe: Now it’s your job to simplify it so you understand that right? [laughter]

Senan: I’m doing my best; give me a break here. So the interesting thing about so we spoke about the spark gap transmitter that Hertz used to prove radio waves. The problem with that of course is that it just sprays a big pile of radio frequency; like practically the entire band is flooded with a signal for a moment. And that’s fine if only one or two people are using radio. But if loads of people want to use radio at the same time they’re all going to interfere with each other because they’re spraying; they’re all on the same band basically; they’re all on every band as it happens.

Joe: Yes.

Senan: And by band I mean so the radio spectrum is kind of divided up into blocks. So you know low frequencies, medium frequencies, high frequencies and so on. The next idea to solve that problem came with something called a continuous wave transmitter. So rather than spraying your radio transmission out on all the bands you try and transmit on a single band; a narrow band or single frequency.

Joe: Right.

Senan: And that means that if the guy next door is transmitting on a different frequency you’re not going to interfere with each other because you’re working you’re using two different frequencies.

Joe: Right.

Senan: So that was necessary; that innovation was necessary to allow lots of people use radio without interfering with each other. And there was a couple of developments that made that possible and…

Joe: Now when are we; have we jumped kind of into the middle of the 20th century now?

Senan: No well we’re still talking about the early 1900s. So the developments I’m about to talk about are about 1904, 1906; that kind of period of time.

Joe: All right okay yeah.

Senan: What is known as a vacuum tube or on this side of the Atlantic sometimes it’s called a valve. You might remember the old TVs had them in the back and you could see this glowing thing.

Joe: No.

Senan: No?

Joe: No I don’t.

Senan: I’m old enough to remember that. There was these glowing yokes in the back of the television. Anyway they weren’t pixies. Okay so the first one of those developments was something that we call a diode. Now I’m not going to go into the details of how it worked but basically…

Joe: Thank god.

Senan: It allowed detecting a radio signal on a particular frequency.

Joe: Right.

Senan: Right it allowed you to tune your receiver to a particular frequency. The second one; a variation of the diode is something called a triode. Now that brought two innovations right? First of all it enabled an amplifier; which means that if you had a very weak signal coming in you could amplify it; make it bigger so that it was loud enough to be heard.

Joe: Right.

Senan: And the other thing; key development was it enabled you to create something called an oscillator which is basically something that generates a single frequency. So now you had a transmitter that could operate on one frequency only and that was able to receive weak signals and make them audible. So those were key innovations that enabled the radios to actually become usable. You; no longer were you using a crude spark gap or a crude vacuum coherer thing with metal filings in it.

Joe: Yes.

Senan: And that enabled Morse code. So you know if you’re if you turn on your transmitter there’s a constant hum; turn it off obviously it stops. So now you can have dots and dashes. So you know you can have a dot is like a short blip; turn on your transmitter for a moment and a dash is a longer blip; turn on on your transmitter for a second or two. And there was a code for every letter of the alphabet. So you can send a sequence of dots and dashes and it’s letters and the receiver, if he understands that, can write down those letters and see what the message is. And even today there’s enthusiasts use that all the time. If you’re able to; if you know which frequencies to tune into you can hear the ham radio enthusiasts actually communicating with each other by Morse.

Joe: Wow. The Ham Radio Morse Code Station.

Senan: Yeah.

Joe: And you thought it was bad listening to us.

Senan: But it’s like a; it’s like a badge of honour to see how many words a minute they can send and all that kind of stuff.

Joe: It really is an amazing gift. I mean like how people can decipher that at speed.

Senan: I have listened to it. The speed of it is unreal. Like I don’t know how anybody can hear what’s going on but people can.

Joe: Yeah. Although if I was listening to it I’d just say I’d just keep hearing "Get a life. Get a life."

Senan: Ah don’t be denigrating ham radio enthusiasts.

Joe: Actually why ham?

Senan: Yeah I don’t know what the origins of that word is.

Joe: Right.

Senan: But it just means amateur radio enthusiasm. And I did look it up before this and I couldn’t find a definitive… like there was theories about what it was but I couldn’t find…

Joe: Was it like short for amateur mispronounced?

Senan: Perhaps. Perhaps.

Joe: Okay.

Senan: Anyway just a very brief digression about Morse code. A kind of a sad anecdote really. So during the Vietnam War lots of American soldiers and officers were imprisoned by the Viet Cong.

Joe: Wow when you go off piste you like you’re going way; way off piste.

Senan: Ah yeah. I shouldn’t be laughing because it is a serious subject. So one of them anyway was forced to make like a propaganda TV programme for the Viet Cong; one of these prisoners. And you know he was forced to say how fantastic the place was and how they were being treated well. But while he was doing that he was blinking in Morse code. And he sent the message "We’re being tortured." Like incredible. Like that he and nobody…

Joe: That is incredible. Yeah.

Senan: His captors didn’t realise what he was doing. It’s so; that was…

Joe: I mean to be able to do it in the first place; to have the wherewithal to do it; to in that scenario to be able to do it. I mean there’s so many levels.

Senan: After having been tortured et cetera you think you’d be so afraid of getting caught. So yeah I can’t of course remember his name but yeah. That was Morse code. Obviously now we can send voice.

Joe: And that’s why you can enjoy our dulcet tones today on the podcast.

Senan: Yeah if somehow or other you are listening to this through old fashioned radio. Yes.

Joe: No. If you’re listening on your phone. Surely. If you’re listening on your phone that’s still radio isn’t it?

Senan: Yeah but the way that voice was originally sent isn’t the way it’s being sent now.

Joe: Okay.

Senan: I mean it’s coming to your phone now as a pile of ones and zeros but that wasn’t always the case.

Joe: Oh because we’re AI. Of course.

Senan: So we needed somehow to be able to get somebody’s voice onto the radio. And you got to remember your carrier wave; your single frequency being generated by an oscillator; it’s just a like turn it on it’s just a hum. There’s no…

Joe: Is a single frequency like a number? It’s just like 200 is a single frequency.

Senan: Yeah so for example 200 kilohertz.

Joe: Yes.

Senan: So that means that if you stand in one place 200,000 of those waves pass you every second.

Joe: Right so that’s the frequency and so that’s one frequency.

Senan: That’s one frequency. So 205 kilohertz is another frequency.

Joe: But is 200.1 a different frequency?

Senan: I don’t know if they go below a single hertz.

Joe: Okay right.

Senan: But so 200.1 kilohertz yeah that’s a valid frequency. Now whether you would have a receiver sensitive enough to tell the difference…

Joe: Yeah.

Senan: With that point one is another matter. But yeah that’s a valid frequency yeah.

Joe: Okay.

Senan: I think before we move on to the wonderful world of voice modulation on radio we might; this might be a good place to call a halt until next week. Because we’ve passed over the half hour mark. We’ve gone through the the history of how radio became a thing.

Joe: So we’ve actually; it’s actually a good place to leave it because we’ve got to the voice modulation on radio while we are…

Senan: Capable of modulating our voices.

Joe: Capable of modulating our voices. Okay so what’s in store next week? Do you want to give us a breakdown?

Senan: So next week we’re going to talk about how voice got included in radio. We’re going to talk about how radio suddenly became essential for safety and then broadcasting. Like you know commercial radio where people could listen to music. And then we’re going to start talking about the way fantastic new developments in electronics brought wonderful capabilities to radio and really dragged it into the modern world to be what it is in your mobile phone that’s in your pocket.

Joe: Wow. Can’t wait for that.

Senan: So yeah that’s a good place to stop. So that’s Enough with the Science for this week. I’m Senan.

Joe: And I’m Joe. Thanks so much for listening.

Senan: Yeah we’ll see you next week.