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