Speaker 1: Brought to you by the reinvented two thousand twelve camera.
Speaker 1: It's ready. Are you get in touch with technology with
Speaker 1: tech Stuff from how stuff works dot com. Hello again, everyone,
Speaker 1: Welcome to tech stuff. My name is Chris Pollett, and
Speaker 1: I'm an editor here at how stuff works dot Com.
Speaker 1: Broadcasting from the seat across from me, as usual, is
Speaker 1: senior writer Jonathan Striffland. You gave them all those old
Speaker 1: time stars through wars of worlds invaded by Mars. You
Speaker 1: made him laugh, you made him cry, you made us
Speaker 1: feel like we could fly. Just remember video killed the
Speaker 1: radio stars. But for now, we're still going to talk
Speaker 1: about radio. Yeah, and you guys might remember not that
Speaker 1: long ago, we did a podcast about who invented the
Speaker 1: radio and we came up with a conclusion of I
Speaker 1: don't know, although actually Chris and I both agreed that
Speaker 1: if if gun were held to our heads, we would
Speaker 1: we would claim that Tesla was the the inventor of
Speaker 1: the radio. It's just that he did not He was
Speaker 1: not able to implement it in the same sort of
Speaker 1: scale as Marconi, whose implementation depended somewhat on Tesla's work.
Speaker 1: But yeah, but it had gone on for some time
Speaker 1: there were a number of people as and and this
Speaker 1: happens a lot in science that uh, you know, their
Speaker 1: contributions made radio possible. They were it was sort of
Speaker 1: invented in increments really. Um. And of course Tesla was
Speaker 1: a very prolific inventor. He had his fingers and lots
Speaker 1: of different pies. I'm sorry, I had to watch Jonathan's
Speaker 1: high clay everyone, and um, I'm having a little moment here.
Speaker 1: And Marconi was was really a radio guy. He really
Speaker 1: was interested in radio. So it's it's really kind of
Speaker 1: no surprise that he really pushed radio very hard, harder
Speaker 1: than Tesla did, and so he got a lot of
Speaker 1: the credit for it. But um, we were going to
Speaker 1: talk today about the invention itself, how radio itself actually works,
Speaker 1: and to really talk about this first we have to
Speaker 1: understand a little bit about radio frequencies, radio waves, and
Speaker 1: uh so let's talk about radio waves first. Now, waves
Speaker 1: are this is a complicated issue because there are different
Speaker 1: types of waves, right. There's there are mechanical waves, which
Speaker 1: are the waves that we can observe with our own
Speaker 1: eyes through various means. Like there's you know, if you
Speaker 1: look at a notion and you see the waves coming across.
Speaker 1: Those are mechanical waves. Due, yes, they are, in fact
Speaker 1: gnarly During an earthquake, the earth moves in mechanical waves, yes,
Speaker 1: and sound travels through mechanical waves. But yeah, now you
Speaker 1: may not think of sound as a mechanical wave because
Speaker 1: it's not something that you can typically see. Although if
Speaker 1: there is a sound loud enough, it can create a
Speaker 1: mechanical wave powerful enough to vibrate uh an objects. So
Speaker 1: you can see that, right, Well, you could see um
Speaker 1: if you've ever watched videos of explosions, especially when a
Speaker 1: video shot from overhead, you can see the shock wave, yeah,
Speaker 1: traveling outward from that, which is you watch any Michael
Speaker 1: bay movie, the moment where the two heroes running away
Speaker 1: from the explosion leap into air and are propelled fifty
Speaker 1: feet that is kind of what Chris is talking about. Okay,
Speaker 1: that was an even better description than the one I
Speaker 1: had Michael Bays solves. Anyway, So yeah, so these waves
Speaker 1: they move, they move, and uh there's a crest and
Speaker 1: then there's a trough, right, the crest being the highest point,
Speaker 1: the trough being the lowest point. And you consider the
Speaker 1: point from the top of one crest to the top
Speaker 1: of the next crest, the wave length of that wave, right,
Speaker 1: all right, So these these mechanical waves, they have to have, uh,
Speaker 1: some sort of of medium to move through. They require that.
Speaker 1: Even sound, which is why if you were to be
Speaker 1: in outer space and you were to take off your
Speaker 1: space helmet and shout to your buddy across the way, Uh,
Speaker 1: your buddy would not hear you, because there is no
Speaker 1: medium there spaces of vacuum. More or less. There are
Speaker 1: particles in space, but they're so far there's there's so little,
Speaker 1: there's no contact. Right. The particles in space are are
Speaker 1: so far apart from one another that there's no way
Speaker 1: to to propagate a mechanical wave through space. I think
Speaker 1: we understand the lack of gravity in this situation, thank you.
Speaker 1: So yeah, nature of hors a vacuum, so do I.
Speaker 1: That's why I only sweep vacuum. So anyway, Yeah, you
Speaker 1: need a medium for a mechanical wave to to move through.
Speaker 1: But electromagnetic waves are different. They do not require that.
Speaker 1: They can they can propagate through a vacuum. They can
Speaker 1: move through the vacuum space and in fact, they will
Speaker 1: continue to move once generated forever. Really Um, so the
Speaker 1: radio waves that we generated way back when we were
Speaker 1: first figuring this out, they are now, oh well, let's see,
Speaker 1: more than around a hundred light years away, because radio
Speaker 1: waves travel at the speed of light. And then you know,
Speaker 1: the invention of the radio really dates back a century.
Speaker 1: So anything around there, anything generated at that time, would
Speaker 1: now be traveling a hundred light years away. It's kind
Speaker 1: of cool. Yeah, yeah, because it travels the speed of light. Okay,
Speaker 1: so all those all those broadcasts in the forties and
Speaker 1: fifties of the radio cereals, those are now forty fifty
Speaker 1: light years away. Cereal. Um yeah, it's Chris's weakness was
Speaker 1: cereal is like my weakness with pie. So don't don't
Speaker 1: get me wrong. I like the pie. So yeah, I
Speaker 1: mean light and and radio waves are both forms of
Speaker 1: electromagnetic radiation. Um, and it's I had something I was
Speaker 1: gonna say there, I've got something here. So when we
Speaker 1: say electromagnetic that's really important. Now, when you're talking about
Speaker 1: a mechanical wave, you're talking about a wave and a
Speaker 1: particular our alignment. Let's let's say vertical, you know, like
Speaker 1: waves you would see on a notion. Electromagnetic waves are
Speaker 1: actually a pair of waves. There's an electric field wave
Speaker 1: and a magnetic field wave. Now you've heard us talk
Speaker 1: a lot about the relationship between electricity and magnetism and
Speaker 1: how there is this interesting connection between the two. As
Speaker 1: it turns out, if you were to generate an electromagnetic wave,
Speaker 1: you would then have a an electric field wave and
Speaker 1: a magnetic field wave moving at the same time, and
Speaker 1: each one replenishes the other. The electric field, because it's
Speaker 1: changing over time, generates a magnetic field. The magnetic field,
Speaker 1: as it changes over time, regenerates the electric field, and
Speaker 1: that's why it can continue at infinitum out into the
Speaker 1: forest reaches of space until it hits the end of
Speaker 1: the universe. Or we started getting reruns of I Love
Speaker 1: Lucy from you know, a billion light years away. Yeah.
Speaker 1: I remember hearing as a kid that the shows that
Speaker 1: we watched we're going to be available out in space,
Speaker 1: like people in Mars with the right equipment. Of course,
Speaker 1: theoretically there aren't any people on Mars. I don't think
Speaker 1: there are. Um, I wouldn't call them people, yeah, exactly. Um,
Speaker 1: but yeah, if you had a TV and you were
Speaker 1: you know, at that point they said, if you're watching
Speaker 1: from Mars right now you would be catching reruns of
Speaker 1: I Love Lucy. This was years ago, but I was going,
Speaker 1: really seriously, that's that's very cool. So, uh, you know,
Speaker 1: I hadn't realized that they would they would do that.
Speaker 1: But on the same by the same token, if you
Speaker 1: think about the giant radio telescopes that they use UM
Speaker 1: to search for extraterrestrial life, some sign that other people
Speaker 1: are using radio frequencies. Basically they're just listening to space
Speaker 1: to see if there is something. I mean, there's there's lots,
Speaker 1: there's noise. Besides, there's something that is generated in a
Speaker 1: in a meaningful way as opposed to UM, because lots
Speaker 1: of stuff produces radio waves, lots and lots of stuff. Uh.
Speaker 1: And really, like I was saying, so, the the was
Speaker 1: talking about electric field and the magnetic fields that that
Speaker 1: are traveling in this electromagnetic wave. UM. The electric fields
Speaker 1: they exert forces on electric charges, magnetic fields exert forces
Speaker 1: on magnetic polls. So these waves can do work because
Speaker 1: they can exert force upon particular things. In the case
Speaker 1: of the electric field, of course, is the electrically charged particles.
Speaker 1: That's the important part for radios. Without that, without the
Speaker 1: the ability to do work. Radios wouldn't work at all.
Speaker 1: We wouldn't be able to pick these things up. And
Speaker 1: uh so that's really a fundamental element that you have
Speaker 1: to understand before we can get into the mechanical and
Speaker 1: technological elements of radio. Uh and uh so let's talk
Speaker 1: a little bit about how how we get a radio
Speaker 1: signal from a transmitter to a receiver. Alright, so you've
Speaker 1: got a radio station and the radio station you are recording,
Speaker 1: or you're you're trying to broadcast some sort of sound signal.
Speaker 1: You are using a microphone, let's say. So let's say
Speaker 1: this is a talk radio. So there's a guy talking
Speaker 1: into a microphone. Uh. The I can't picture that, right, Yeah,
Speaker 1: it's so hard to understand when you're facing someone doing it. Uh.
Speaker 1: The mechanical waves from the sound of the voice go
Speaker 1: into the microphone. They hit a little diaphragm which then
Speaker 1: uh manipulates an electric charge, creating a frequency within that
Speaker 1: electric charge, which then goes to a I'm simplifying here,
Speaker 1: but but it goes to a transmitter, which then changes
Speaker 1: this electric charge into one of two different um uh
Speaker 1: kinds of radio signals. You've probably heard of a M
Speaker 1: and FM. Yes, well it's not just two, but those
Speaker 1: are the two weeks, those are the two years for broadcast. Yeah,
Speaker 1: for for broadcast radio. Yes, yes, I'm I'm specifically talking
Speaker 1: about the kind of radios where you tune in to
Speaker 1: listen to music or or or talk or whatever. It's
Speaker 1: not I'm not talking citizens band, I'm not talking any
Speaker 1: of the other other kind of UM. Yeah, So, uh,
Speaker 1: the way you you transmit information across those radio waves
Speaker 1: depends on whether you're using a M or FM radio. Right,
Speaker 1: you have to have a carrier wave, which is a
Speaker 1: frequent a radio frequency wave that is able to hold
Speaker 1: information and take it from the transmitter to the receiver. UM.
Speaker 1: And basically it sort of depends on the frequency and amplitude.
Speaker 1: That's that's exactly what a M and FM are. Its
Speaker 1: amplitude modulation and frequency modulation. So with amplitude modulation, you
Speaker 1: remember we were talking about a wave. You know, you
Speaker 1: have the crests the trough, and the from crest to
Speaker 1: crest is wavelength. Well, the the height I guess you
Speaker 1: could say the height of the crests or the depth
Speaker 1: of the trough, which are equivalent in the case of
Speaker 1: these waves. UM. That is the amplitude, right. The bigger
Speaker 1: the amplitude, the the taller those those waves are going
Speaker 1: to look when you look at them as a wavelength. UM.
Speaker 1: So with amplitude modulation, it's exactly what sounds like. You
Speaker 1: you modify the amplitude to contain the uh, the information
Speaker 1: that you're transmitting. When that information is received by a radio,
Speaker 1: I'm gonna skip a little bit here. We're gonna go
Speaker 1: back to the middle section in a minute. But when
Speaker 1: your radio receives an A M signal, it's going to
Speaker 1: detect it's going to detect the the height of those waves.
Speaker 1: And as the height changes over time, that's going to
Speaker 1: give the speaker in your radio the signal to move
Speaker 1: in or out, and your speaker cone technically your speaker
Speaker 1: cone in the speaker. As the speaker cone in your
Speaker 1: speaker moves in and out, that's what generates the sound
Speaker 1: you hear. So as those waves go up and uh
Speaker 1: down in in amplitude uh, and they're gonna be doing
Speaker 1: this uh thousands of of times per second because along
Speaker 1: with the the crest trough and wavelength, you have the frequency.
Speaker 1: The frequency is how many uh, how many cycles, how
Speaker 1: many wavelengths you go through within a second. We call
Speaker 1: that like, if you were to do one cycle a
Speaker 1: second would be one hurts, right, so it kill hurts
Speaker 1: is one thousand cycles in a second. A mega hurts
Speaker 1: would be a million cycles in a second, a giga
Speaker 1: hurts would be a billion cycles in a second. So
Speaker 1: that's a lot. So you're at home. The radio has
Speaker 1: detected the signal and it's detecting the difference in that amplitude,
Speaker 1: and as that amplitude changes over time, that's what tells
Speaker 1: the speaker how to uh to move in and out
Speaker 1: and generate the sound that you hear. Frequency modulation is different.
Speaker 1: The amplitude remains the same, it remains steady h So
Speaker 1: you don't change the amplitude. That's not what tells the
Speaker 1: speaker what the how to interpret that's that's signal to
Speaker 1: turn it into sound. Instead, you you change the frequency
Speaker 1: itself of the transmission, which is a little tricky because
Speaker 1: to tune a radio you have to tune it into
Speaker 1: a specific frequency to to really pick up a good signal. UH.
Speaker 1: So it really generates it keeps it within a fairly
Speaker 1: tight set of parameters. It can't go far beyond that,
Speaker 1: or else you would no longer be able to pick
Speaker 1: up the radio station. But by changing the frequency, that
Speaker 1: is the the number of cycles that UM wavelength goes
Speaker 1: through in a second, that's what tells the speaker how
Speaker 1: to move in and out and generate the sound you hear.
Speaker 1: Now we have to tackle the magical bit in the middle. Okay,
Speaker 1: you know, so we've got you know, you've generated the
Speaker 1: sound and you've heard the sound. But what's happening between
Speaker 1: those two moments and there's some fascinating stuff here, and
Speaker 1: we're gonna get into some science. Uh So, some apologies
Speaker 1: to uh to Robert and Julie who would normally tackle
Speaker 1: this kind of thing, but we're gonna do it. Um. So,
Speaker 1: when you generate that signal at the transmitter, you actually
Speaker 1: create an electric charge that moves up and down your
Speaker 1: transmitter antenna. All right. So antenna are used for two
Speaker 1: main purposes, to transmit signals and to receive signals. Yep.
Speaker 1: And it's true too that, uh the type of frequency
Speaker 1: you're using requires a different type of antenna. For example,
Speaker 1: if you're broadcasting AM versus FM, it requires a different
Speaker 1: antenna length because that has a lot to do with it.
Speaker 1: And and if you've always wondered why, uh, you know,
Speaker 1: I have a clock radio and it's got it basically
Speaker 1: has an internal AM antenna, but it's got an external
Speaker 1: FM antenna. And I didn't understand why until I you know,
Speaker 1: I just really didn't care to look until we were
Speaker 1: deciding to do this. And yeah, it has a lot
Speaker 1: to do with the exactly what we were just talking
Speaker 1: about or what you were just talking about, which is, uh,
Speaker 1: the ways in which they and the carrier wave is
Speaker 1: transmitted in these different technologies, so you know, you need
Speaker 1: a different kind of antenna to transmit and to receive
Speaker 1: those signals depending on what you're trying to do. And
Speaker 1: in general, a general rule of thumb is the best
Speaker 1: antenna to receive a signal is one quarter of the
Speaker 1: length of the radio waves wavelength. But here's the thing.
Speaker 1: AM radio that gets big. I mean AM radio can
Speaker 1: be uh so big. That's larger than a football field.
Speaker 1: And so having an AM radio antenna receiver antenna that's
Speaker 1: a quarter the size of a football field is not
Speaker 1: really on most people's list of home improvement UM projects.
Speaker 1: So there are ways around that, but that's the ideal
Speaker 1: length for a reception antenna. Now, when you when you
Speaker 1: create this electric charge that's going up and down the
Speaker 1: the antenna, you're actually you're using an oscillator to change
Speaker 1: the charge. So you're you're essentially switching the charge. You're
Speaker 1: you're switching voltage on and off up and down this
Speaker 1: this antenna, and that electric charge has it changes over
Speaker 1: time up and down the antenna. That's what creates the
Speaker 1: electromagnetic wave that propagates out from the the transmitter antenna.
Speaker 1: You know, I've watched a lot of movies where um uh,
Speaker 1: you know you've got your giant radio antenna and these
Speaker 1: little electrical things come out the top. You mean that's
Speaker 1: not exactly right. No, you're thinking of our ko Ka
Speaker 1: the old arcade. Yeah, no, you can't see them, although
Speaker 1: it was. Although here's Here's the interesting thing though, is
Speaker 1: that you can pick up you can receive electricity this way,
Speaker 1: although it's a minuscule amount. In fact, that's that's the
Speaker 1: basis of why this ends up working. So you you
Speaker 1: pump lots and lots of electricity into this antenna. We're
Speaker 1: talking about thousands of watts for for an a m station,
Speaker 1: and you are using an oscillator to to move that
Speaker 1: that electric charge up and down the antenna at a
Speaker 1: certain rate. And UH, at that rate depends upon what
Speaker 1: the FCC in the United States has designated as your
Speaker 1: broadcast range. You broadcast your signal that way. Now, let's
Speaker 1: say you want to pick that signal up. The electromagnetic waves, UH,
Speaker 1: move out from that antenna, their directional, they move out
Speaker 1: in every direction really from the antenna. Uh. And then
Speaker 1: you are a certain distance away. You have your radio,
Speaker 1: You've got your antenna extended up. As the electromagnetic waves
Speaker 1: move towards your antenna, your antenna actually can we'll pick
Speaker 1: up a little electrical charge because you've got you know,
Speaker 1: the antenna. That's the whole reason why the radio works
Speaker 1: is that electric field is able to enact the work
Speaker 1: on an electric charge. You've got a little electric charge
Speaker 1: inside that antenna. It alters. But due to this radio wave,
Speaker 1: and assuming that you have your radio tune to the
Speaker 1: right station, UH, what's gonna happen is the electric charge
Speaker 1: in your antenna, your receptor antenna is going to move
Speaker 1: up and down a certain frequency. If you have tuned
Speaker 1: your radio properly, it's going to be at the circuit
Speaker 1: in your radio is gonna be at a resonant frequency
Speaker 1: with that charge that's moving up and down in your antenna. Now,
Speaker 1: if you've heard about resonant frequencies, that's when you can
Speaker 1: uh make something essentially vibrate at uh an ideal frequency
Speaker 1: for stuff to go crazy like we we've seen. You know,
Speaker 1: you might have seen a MythBusters episode where they started
Speaker 1: talking about resonant frequencies. Yes, the idea being that us
Speaker 1: should wind blow across a bridge at a particular frequency
Speaker 1: of a particular speed. It would create this uh, this
Speaker 1: sort of uh vicious cycle that feeds into itself where
Speaker 1: the bridge itself starts to shake apart. Well, resonant frequencies
Speaker 1: are a real thing, and if you do generate uh
Speaker 1: the right resonant frequency, you can create a larger and
Speaker 1: larger um uh vibrations in a medium. So think of
Speaker 1: it kind of like you've got a kid on a
Speaker 1: swing and you're pushing the kid on the swing. If
Speaker 1: you push the kid at just the right time, the
Speaker 1: kid's gonna go up higher each on each swing, Right,
Speaker 1: You're you're adding more energy into it, and it's and
Speaker 1: uh you see the output as the kid goes up higher.
Speaker 1: If you push it the wrong time, the kid just
Speaker 1: ends up drinking around and falling off the swing set
Speaker 1: and crying like like I did. Thanks Dad. Anyway, uh So,
Speaker 1: the the circuit in your radio, when you tune it,
Speaker 1: you actually alter the circuit a little bit so that
Speaker 1: it will resonate at a different frequency once it hits
Speaker 1: the right frequency for the radio wave that's hitting your antenna.
Speaker 1: Those little uh the electric charge is going up and
Speaker 1: down your your antenna will cause a larger reaction within
Speaker 1: the circuit in your radio, which is what you're is
Speaker 1: picked up by the amplifier and then converted into um
Speaker 1: sound through your speaker. Yeah. Yeah, So should we get
Speaker 1: into some of the other cool stuff? Yeah, like hit
Speaker 1: me with stereo. Oh man, I didn't even go into stereo.
Speaker 1: I was. I was so concentrated on I want to
Speaker 1: make sure I can explain the science of how this
Speaker 1: radio wave moves across. Um. It's actually really fascinating stuff.
Speaker 1: And all, you know what we should do before we
Speaker 1: talk about stereo. Crystal radio. Okay, that's the simplest kind
Speaker 1: of radio I can think of. As a matter of fact. Um,
Speaker 1: when I was a kid, I had I probably still
Speaker 1: do in the box somewhere a crystal radio kit. UM.
Speaker 1: And yeah, when I was when I was doing a
Speaker 1: little research. UM, one of the things that really lead
Speaker 1: to radio being functional was UM the ability to when
Speaker 1: they discovered the ability to tune a radio. It's like
Speaker 1: I I don't want to just search for whatever. I
Speaker 1: want to be able to lock it in to to
Speaker 1: detect a specific UH signal. And and when they developed
Speaker 1: the ability to tune a radio, that basically made UM
Speaker 1: what is what is now the radio industry possible because
Speaker 1: you can tune into a specific UH station and leave
Speaker 1: it there and it's not going anywhere. UM. Of course,
Speaker 1: you have to be very careful, especially if you're the
Speaker 1: the licensing group. UM. Here in Atlanta there are tons
Speaker 1: and tons of radio stations. And I had this problem
Speaker 1: with UM. UM. I had an iPod with a broadcaster
Speaker 1: that I used to use trying to play through my
Speaker 1: radio rather than you know, hooking it up in some
Speaker 1: way physically with a tape adapter or a plug or
Speaker 1: something like that. And UH, you know, you have to
Speaker 1: have a certain distance between stations for the signal not
Speaker 1: to for the carrier waves not to bleed over and
Speaker 1: and basically muddle the information in between. And I had
Speaker 1: as I would drive around Atlanta, I would have to
Speaker 1: change the station that my iPod broadcaster was broadcasting on
Speaker 1: because um, you know, I would start to enter another
Speaker 1: station more powerful signal would start to interfere with it,
Speaker 1: and I would have to to do that. UM. So yeah,
Speaker 1: this the crystal set that's really really basic. UM. In fact,
Speaker 1: the one I got from radio Shack was basically, uh,
Speaker 1: it was already hooked up, so to speak. It had
Speaker 1: It was one of those that has the springs and
Speaker 1: you you connect the wires using the springs. And if
Speaker 1: you haven't seen these kits, um, you know, basic electronics
Speaker 1: type kits. There's a h the board is wired underneath
Speaker 1: and there are very tight, tightly coiled springs installed in
Speaker 1: the top. And to make a connection from one point
Speaker 1: to the other to finish your kit build the radio.
Speaker 1: In this case, UM, you have wires that are um
Speaker 1: uh not insulated on the very ends and you bend
Speaker 1: the spring stick the end of the metal end of
Speaker 1: the wire and let go and the spring holds it
Speaker 1: into place. UM. And with that, you know, and I
Speaker 1: had a long wire that I would use to pick
Speaker 1: up a M signals. That would be your antenna. The antenna.
Speaker 1: But yeah, if you're you know, if you don't know
Speaker 1: what's going on, it looks sort of a lot the
Speaker 1: other wires in the kit, but you know, you'd have
Speaker 1: to extend it away, and and a small knob that
Speaker 1: you would use to tune that. But it also had
Speaker 1: a coil of metal. It looked like electromagnet. Yeah, I
Speaker 1: can actually talk a little bit about that. There are
Speaker 1: four basic components of a crystal radio. These are These
Speaker 1: are literally the only four things you need to make
Speaker 1: the most basic a M radio. You need an antenna,
Speaker 1: so some sort of wire to act as an antenna.
Speaker 1: That you need a tank circuit, which is what looked
Speaker 1: like the electro magnet to you, I'm guessing, yes, you
Speaker 1: need a diode, and and then you need an earphone
Speaker 1: of some sort. In this case it was hardwired in
Speaker 1: was one of those petty color uh you know, yeah,
Speaker 1: and the and the and you don't need a battery.
Speaker 1: And the reason you don't need a batteries because, like
Speaker 1: I said, when you have the antenna, the electromagnetic field
Speaker 1: will cause an electric charge to move up and down
Speaker 1: that antenna on its own, it don't. You don't need
Speaker 1: a battery to create that electricity from the start. Now,
Speaker 1: the signal you're going to receive will be very weak,
Speaker 1: even unless well the closer you get to the to
Speaker 1: the radio station, the more powerful the signal will be,
Speaker 1: but still be pretty weak. And but you're the human
Speaker 1: ear is remarkably sensitive, so you'll be able to hear
Speaker 1: the transmission even if the signal itself is weak. By
Speaker 1: the way, Uh, this the fact that you are able
Speaker 1: to to collect in a way, or that you're able
Speaker 1: to receive electricity over the air this way, that was
Speaker 1: one that was one thing that Tesla was obsessed about
Speaker 1: the idea of broadcasting electricity and too, you're gonna find
Speaker 1: if you do a search online, you'll find some um wow,
Speaker 1: to call them Charlottean's might be too strong a word,
Speaker 1: but you'll find some people who claim that they have
Speaker 1: created a way to generate electricity through or transmit electricity
Speaker 1: through through broadcast using this method. Well, it's true that
Speaker 1: you can get electricity this way, but it's on such
Speaker 1: a tiny amount that you would need a receptor antenna
Speaker 1: that would be enormous in order to generate to receive
Speaker 1: enough electricity for it to be enough to power a
Speaker 1: light bulb even yeah, be basically a trickle. Yeah. So
Speaker 1: so it's it's it's more likely than not if you
Speaker 1: see someone who says that they have this new free
Speaker 1: energy type thing where you're just gonna be pulling in
Speaker 1: radio waves and changing that into electricity. And since since
Speaker 1: so many things out in the universe create radio waves,
Speaker 1: therefore it's almost free energy, be on alert because that's
Speaker 1: not exactly true. I mean, you will get electricity that way,
Speaker 1: but it won't be enough to do any real significant
Speaker 1: work anyway. So you've got those four basic UH components.
Speaker 1: So so the antenna UH projects up. It collects the
Speaker 1: electromagnetic or into the electromagnetic fields that's passing by UM,
Speaker 1: and then that creates the difference in charge up and
Speaker 1: down the antenna. And then you've got the tank circuit,
Speaker 1: which is it's a coil of wire and it's connected
Speaker 1: at each end to the two ends of a capacitor.
Speaker 1: So you've got a capacitor and UH and a coil
Speaker 1: of wire. That's what a tank circuit is. And generally
Speaker 1: the way you tune a radio is that you either
Speaker 1: alter the coil, or you alter the capacitor, one of
Speaker 1: the two most radios they work on. You know you
Speaker 1: you are are changing one of those two elements in
Speaker 1: order to tune the radio. Um. The diode is an
Speaker 1: interesting electrical component. I'm not sure that we may have
Speaker 1: talked about it in our Basics of Electronics podcast, but
Speaker 1: I can't remember exactly I want to say we did.
Speaker 1: But a diode it kind of a it's it's something
Speaker 1: that allows electricity to flow one direction but not the
Speaker 1: other way. It's like a it's like a one way
Speaker 1: street in a way, and using that connected to the
Speaker 1: tank circuit, and then you have the earphone connected through there.
Speaker 1: That's what allows you to have have the right electric
Speaker 1: signals sent to the earphone that then oscillates at the
Speaker 1: right frequency to create the sound, and then you can
Speaker 1: hear it. Although again it's gonna be very very faint.
Speaker 1: It's not gonna be like, you know, hey, is that
Speaker 1: freedom rockman? Will turn it up? Man? Do you remember
Speaker 1: those commercials our listeners don't anyway for them? Yeah, you're
Speaker 1: better off for it, but uh so, yes, so that
Speaker 1: that I just wanted to talk about that since it's
Speaker 1: the most basic and our listeners. If you're interested, you
Speaker 1: can actually go out and find components and build one
Speaker 1: of these yourselves. Uh. There's some places that sell the
Speaker 1: kits um. Depending upon the electronics stores that maybe in
Speaker 1: your area, you might even be able to buy the
Speaker 1: the individual components and and build your own AM radio
Speaker 1: from scratch that way. Now, keep in mind again this
Speaker 1: is a very uh primitive and therefore um limited piece
Speaker 1: of technology, and your your experience with it will depend
Speaker 1: heavily on how close you are to the nearest a
Speaker 1: UM transmitters, because the further way you are, the weaker
Speaker 1: that signal is going to be, and it may get
Speaker 1: to the point where you just can't get enough of
Speaker 1: a signal to be able to hear the transmission. UM.
Speaker 1: So yeah, I had a number of other related things
Speaker 1: that I had been curious about. UM. One of them
Speaker 1: was stereo, although not as much together. And stereo is
Speaker 1: actually fairly simple um because basically you have the two
Speaker 1: you have two microphones you absolutely uh well this will
Speaker 1: be obvious really when you think about it. The stereo
Speaker 1: signal has two separate channels, you know, one for the
Speaker 1: left one for the right. UM. So that means you
Speaker 1: would need more than one microphone, and uh, the trick
Speaker 1: is that you have to you know, it essentially works
Speaker 1: the same way that you have two feeds going into
Speaker 1: the box and you know they go from the box
Speaker 1: to the tower and through the air and back to
Speaker 1: the thing. The thing is you have to make sure
Speaker 1: that the wave is able to carrier wave is able
Speaker 1: to handle that. And for a long time that was
Speaker 1: only possible through frequency modulation UM just because it has
Speaker 1: more capacity UM than AM UM. And you know, we
Speaker 1: really didn't talk about the frequencies used. That's true. We
Speaker 1: talked about in our CB radio I think I remember
Speaker 1: we did talk about the electromagnetic spectrum and we talked
Speaker 1: about which parts of the spectrum were allowed for H
Speaker 1: for radio use. Yeah yeah, and that was years ago.
Speaker 1: Yeah yeah, but yeah, you need that. That's one of
Speaker 1: the reasons why. And I know that they were able
Speaker 1: they promoted AM stereo some years ago. UM. But basically
Speaker 1: the difference being that the frequency modulation signal is able
Speaker 1: to carry more information. Therefore you can UH, you can
Speaker 1: do that, but you have to UH to make it
Speaker 1: possible and then carrier wave to carry a stereo signal
Speaker 1: with more than one UH channel of information. Um, you
Speaker 1: want to talk about the ionosphere any I was gonna
Speaker 1: just mention that the ion a sphere. Uh. You might
Speaker 1: wonder why at night you can hear radio stations much
Speaker 1: further away, or at least in the evening, late evening
Speaker 1: at dusk you can hear radio stations much further away
Speaker 1: than normal, and that that does have to do with
Speaker 1: the ionosphere. And uh, the ionosphere has its own sort
Speaker 1: of Uh. Well, it's it's like an electric mirror in
Speaker 1: a way. If if radio waves of a particular uh
Speaker 1: frequency and and wavelength hit the ionosphere, they could be
Speaker 1: reflected back down toward the Earth. And you can actually
Speaker 1: bounce a radio signal off the ionosphere and back towards
Speaker 1: the surface of the planet, and therefore it will travel
Speaker 1: much further than it would just through line of sight. Yeah,
Speaker 1: they discovered that in two Um. There were there were
Speaker 1: a couple of people who were involved with that. Arthur
Speaker 1: Edwin Kennelly who was an electrical electrical engineer in the
Speaker 1: United States, and Oliver Heaviside from UH from England, was
Speaker 1: a mathematician. Um. Again one of those situations. Uh, there
Speaker 1: seems to be a lot of that in radio where
Speaker 1: people sort of simultaneously discovered this UM and I got
Speaker 1: lot of information from the article about radio and Britannica.
Speaker 1: This is where I picked this particular bit up. But yeah,
Speaker 1: they were the ones who u Ino had figured out
Speaker 1: that UM you could basically transmit towards the sky and
Speaker 1: the iono sphere would refract them back towards Earth and
Speaker 1: that would help you extend the range of your transmitting. Yeah,
Speaker 1: it's it's interesting because and during the daytime, the ionosphere,
Speaker 1: the the electrically charged particles in the ionosphere, they don't
Speaker 1: act as a very good electrical conductor. Uh. It's only
Speaker 1: really once you hit UH in the early evening that's
Speaker 1: when the conductivity actually improves. And we don't the ionosphere,
Speaker 1: the magnetosphere, these elements of the the Earth's uh hesitate
Speaker 1: to use the word ecosystem, but the these elements connected
Speaker 1: to Earth are still things that we are learning about today.
Speaker 1: So we don't have all the information on it because
Speaker 1: scientists are still really building on the knowledge that we
Speaker 1: already have. You gotta keep in mind that until until
Speaker 1: a little over a hundred years ago, we didn't even
Speaker 1: know these things existed, at least not in the way
Speaker 1: we do now, and not in the level of detail, right.
Speaker 1: I mean, we knew that compass has worked, but there
Speaker 1: was you know, our our level of knowledge about the
Speaker 1: magnetosphere was limited. We didn't know anything of the geomagnetic
Speaker 1: storms and uh and how the Sun can affect our
Speaker 1: own magnetosphere. So this is information that we're still building
Speaker 1: on today. But yeah, so and in the evening, the
Speaker 1: conductivity improves. That's what allows the the A M waves
Speaker 1: to to bounce off the ionosphere and back on the Earth.
Speaker 1: FM waves. By the way, the uh, the wavelength is
Speaker 1: too small and the frequencies too high, they actually just
Speaker 1: passed right through the atmosphere. They don't they don't bounce
Speaker 1: back down. So that's why FM stations you aren't. You
Speaker 1: aren't going to get that same effect. It's not like
Speaker 1: at night you're gonna start picking up the FM station
Speaker 1: from the city, you know, a hundred miles away, when
Speaker 1: normally you'd have to be on top of the city
Speaker 1: to pick it up. It's just not gonna happen. Yeah,
Speaker 1: and um, I mean there are there are a lot
Speaker 1: of differences too. I mean, you don't notice that the
Speaker 1: changes um at nighttime with FM, so in such a
Speaker 1: pronounced fashion. Le's not in my experience as you do
Speaker 1: with AM. UM. There are a lot of things that
Speaker 1: you can detect. AM is a lot more finicky. Also,
Speaker 1: some radio gets dirtier at night. I noticed that, not
Speaker 1: the programming. Oh sorry, I was thinking about all the
Speaker 1: songs that I hear once, you know, once the primetime. Okay,
Speaker 1: I'm clearly I'm off off base here, so but uh
Speaker 1: but yeah. And also that the direction. You know, there
Speaker 1: were in the United States clear channel stations that were
Speaker 1: given more range, you know, to to go ahead and
Speaker 1: keep broadcasting full strength at night, UM, whereas other stations
Speaker 1: were asked to back off at certain times of the day. UM.
Speaker 1: And something else I wanted to I know, we're getting
Speaker 1: towards the end of our time, but something else I
Speaker 1: wanted to, uh to point out was if you've ever
Speaker 1: been in a car are like mine, for example, where
Speaker 1: you want to tune into an AM station and it's
Speaker 1: just a pain in the neck because you get a
Speaker 1: lot of static. Well with that FIM stations you don't
Speaker 1: have the interference from all kinds of things like for example,
Speaker 1: UM power lines or lightning or lightning or in some
Speaker 1: cases UM I would assume it's the rebar and overpasses
Speaker 1: and stuff like that. Um, you know that are interfering
Speaker 1: with your signal. You'll go under something and you get it,
Speaker 1: you know sort of thing. Maybe they're electrical wires in
Speaker 1: there that I didn't notice. But also spark plugs. My
Speaker 1: spark plugs interfere with the AM signal. You know, if
Speaker 1: you are in an area that has a lot of antenna,
Speaker 1: you can actually get interference because the antenna, as the
Speaker 1: electrical charge moves up and down the antenna while you're
Speaker 1: receiving it, it's being it's being created by the electromagnetic field.
Speaker 1: That means your antenna is also creating an electromagnetic field.
Speaker 1: It's much it's a much lower powered electromagnetic field, but
Speaker 1: there are enough antenna packed into a small enough space
Speaker 1: that can create interference, uh for him, especially for AM transmissions. Yeah,
Speaker 1: but but I have a station that I try to
Speaker 1: listen to on a m every once in a while
Speaker 1: and um, you know, catch the game from the local
Speaker 1: sports team. And uh apparently yeah, um, apparently the the
Speaker 1: spark plug in your car will when it fires, it
Speaker 1: creates interference in a very high frequency range, which is
Speaker 1: the thirty mega hurts range, and that's just at the
Speaker 1: right frequency to seriously irritate the the AM signal and
Speaker 1: cause problems. You know what's that that one right there?
Speaker 1: Sorry everybody, I just blew up our listeners ears that
Speaker 1: in the sixty cycle. Hum, Hey, Casey, can you lower
Speaker 1: that a little bit so that they don't they don't
Speaker 1: all write to me and complain thanks, You can just
Speaker 1: uh if if the answer is yes, lower it a
Speaker 1: little the answer is no, I'll direct all emails to Casey. Alright.
Speaker 1: So there's a lot more to radio. There's tons more
Speaker 1: and then and it gets into quite a bit of detail. Yeah,
Speaker 1: but like I said, we we kind of gave the
Speaker 1: the bird's eye view of the science on this. So
Speaker 1: but it's really fascinating stuff. We do have an article
Speaker 1: on the site about how radio works. Um, there are
Speaker 1: plenty of other sites out there that that discuss radio
Speaker 1: and the technology behind it, the science behind it. Uh.
Speaker 1: There's a Center for Cosmological Physics has a a great
Speaker 1: summary on it. It was it was for a summer program, uh,
Speaker 1: the Yerkey's Summer Institute two thousand two program. But they
Speaker 1: have a a PDF document that's available online. So if
Speaker 1: you do a search for uh cosmological physics radio wave basics,
Speaker 1: it'll tell you not just the radio wave basics the
Speaker 1: science behind it, but also the actual basics behind radios themselves.
Speaker 1: So that's a that's a helpful guide, and it was
Speaker 1: it was made for science classes who were going out
Speaker 1: and actually doing creating their own radios and kind of
Speaker 1: explaining the science behind it. So I recommend a read
Speaker 1: of that if if you want to get a little
Speaker 1: more information. And of course, like I said, there's tons
Speaker 1: of of of references out there on the web that
Speaker 1: you can use. So we're gonna wrap this discussion up.
Speaker 1: If you guys have any suggestions for topics that we
Speaker 1: should tackle, let us know on Twitter and Facebook are handled.
Speaker 1: There is tech Stuff hs W, or you can send
Speaker 1: us an email and that address is text stuff at
Speaker 1: how stuff works dot com. Chris and I will talk
Speaker 1: to you again really soon. Be sure to check out
Speaker 1: our new video podcast, Stuff from the Future. Join how
Speaker 1: Stuff Work staff as we explore the most promising and
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