WEBVTT - How Radio Works 0:00:00.320 --> 0:00:02.880 Brought to you by the reinvented two thousand twelve camera. 0:00:03.200 --> 0:00:09.000 It's ready. Are you get in touch with technology with 0:00:09.080 --> 0:00:17.920 tech Stuff from how stuff works dot com. Hello again, everyone, 0:00:17.960 --> 0:00:20.880 Welcome to tech stuff. My name is Chris Pollett, and 0:00:20.920 --> 0:00:23.360 I'm an editor here at how stuff works dot Com. 0:00:23.480 --> 0:00:26.079 Broadcasting from the seat across from me, as usual, is 0:00:26.160 --> 0:00:29.319 senior writer Jonathan Striffland. You gave them all those old 0:00:29.320 --> 0:00:33.000 time stars through wars of worlds invaded by Mars. You 0:00:33.000 --> 0:00:35.680 made him laugh, you made him cry, you made us 0:00:35.680 --> 0:00:42.159 feel like we could fly. Just remember video killed the 0:00:42.240 --> 0:00:46.200 radio stars. But for now, we're still going to talk 0:00:46.200 --> 0:00:49.720 about radio. Yeah, and you guys might remember not that 0:00:49.760 --> 0:00:52.280 long ago, we did a podcast about who invented the 0:00:52.360 --> 0:00:55.640 radio and we came up with a conclusion of I 0:00:55.680 --> 0:00:59.640 don't know, although actually Chris and I both agreed that 0:00:59.680 --> 0:01:02.600 if if gun were held to our heads, we would 0:01:02.920 --> 0:01:06.800 we would claim that Tesla was the the inventor of 0:01:06.840 --> 0:01:09.080 the radio. It's just that he did not He was 0:01:09.120 --> 0:01:12.119 not able to implement it in the same sort of 0:01:12.360 --> 0:01:17.520 scale as Marconi, whose implementation depended somewhat on Tesla's work. 0:01:17.840 --> 0:01:20.600 But yeah, but it had gone on for some time 0:01:20.680 --> 0:01:22.640 there were a number of people as and and this 0:01:22.680 --> 0:01:26.120 happens a lot in science that uh, you know, their 0:01:26.120 --> 0:01:29.240 contributions made radio possible. They were it was sort of 0:01:29.360 --> 0:01:33.920 invented in increments really. Um. And of course Tesla was 0:01:33.959 --> 0:01:38.199 a very prolific inventor. He had his fingers and lots 0:01:38.240 --> 0:01:42.760 of different pies. I'm sorry, I had to watch Jonathan's 0:01:42.800 --> 0:01:46.319 high clay everyone, and um, I'm having a little moment here. 0:01:46.400 --> 0:01:50.400 And Marconi was was really a radio guy. He really 0:01:50.440 --> 0:01:53.200 was interested in radio. So it's it's really kind of 0:01:53.200 --> 0:01:57.480 no surprise that he really pushed radio very hard, harder 0:01:57.480 --> 0:02:00.360 than Tesla did, and so he got a lot of 0:02:00.360 --> 0:02:03.600 the credit for it. But um, we were going to 0:02:03.640 --> 0:02:08.240 talk today about the invention itself, how radio itself actually works, 0:02:08.280 --> 0:02:10.320 and to really talk about this first we have to 0:02:10.919 --> 0:02:16.400 understand a little bit about radio frequencies, radio waves, and 0:02:16.520 --> 0:02:22.799 uh so let's talk about radio waves first. Now, waves 0:02:22.840 --> 0:02:26.000 are this is a complicated issue because there are different 0:02:26.040 --> 0:02:29.320 types of waves, right. There's there are mechanical waves, which 0:02:29.360 --> 0:02:31.680 are the waves that we can observe with our own 0:02:31.680 --> 0:02:33.800 eyes through various means. Like there's you know, if you 0:02:34.080 --> 0:02:36.560 look at a notion and you see the waves coming across. 0:02:36.800 --> 0:02:40.680 Those are mechanical waves. Due, yes, they are, in fact 0:02:40.800 --> 0:02:45.120 gnarly During an earthquake, the earth moves in mechanical waves, yes, 0:02:45.720 --> 0:02:50.880 and sound travels through mechanical waves. But yeah, now you 0:02:50.919 --> 0:02:52.920 may not think of sound as a mechanical wave because 0:02:52.960 --> 0:02:55.240 it's not something that you can typically see. Although if 0:02:55.240 --> 0:02:57.400 there is a sound loud enough, it can create a 0:02:57.400 --> 0:03:01.000 mechanical wave powerful enough to vibrate uh an objects. So 0:03:01.040 --> 0:03:03.680 you can see that, right, Well, you could see um 0:03:03.760 --> 0:03:10.120 if you've ever watched videos of explosions, especially when a 0:03:10.200 --> 0:03:14.440 video shot from overhead, you can see the shock wave, yeah, 0:03:14.560 --> 0:03:17.520 traveling outward from that, which is you watch any Michael 0:03:17.520 --> 0:03:20.880 bay movie, the moment where the two heroes running away 0:03:20.880 --> 0:03:23.519 from the explosion leap into air and are propelled fifty 0:03:23.600 --> 0:03:26.240 feet that is kind of what Chris is talking about. Okay, 0:03:26.240 --> 0:03:28.480 that was an even better description than the one I 0:03:28.520 --> 0:03:35.400 had Michael Bays solves. Anyway, So yeah, so these waves 0:03:35.400 --> 0:03:38.640 they move, they move, and uh there's a crest and 0:03:38.680 --> 0:03:41.680 then there's a trough, right, the crest being the highest point, 0:03:41.680 --> 0:03:44.480 the trough being the lowest point. And you consider the 0:03:44.640 --> 0:03:47.120 point from the top of one crest to the top 0:03:47.200 --> 0:03:51.240 of the next crest, the wave length of that wave, right, 0:03:51.320 --> 0:03:54.320 all right, So these these mechanical waves, they have to have, uh, 0:03:54.720 --> 0:03:58.720 some sort of of medium to move through. They require that. 0:03:58.840 --> 0:04:01.400 Even sound, which is why if you were to be 0:04:01.440 --> 0:04:03.680 in outer space and you were to take off your 0:04:03.760 --> 0:04:07.240 space helmet and shout to your buddy across the way, Uh, 0:04:07.400 --> 0:04:10.080 your buddy would not hear you, because there is no 0:04:10.720 --> 0:04:14.160 medium there spaces of vacuum. More or less. There are 0:04:14.240 --> 0:04:18.159 particles in space, but they're so far there's there's so little, 0:04:19.400 --> 0:04:22.200 there's no contact. Right. The particles in space are are 0:04:22.360 --> 0:04:25.000 so far apart from one another that there's no way 0:04:25.040 --> 0:04:28.600 to to propagate a mechanical wave through space. I think 0:04:28.640 --> 0:04:31.040 we understand the lack of gravity in this situation, thank you. 0:04:31.360 --> 0:04:34.080 So yeah, nature of hors a vacuum, so do I. 0:04:34.480 --> 0:04:38.800 That's why I only sweep vacuum. So anyway, Yeah, you 0:04:38.839 --> 0:04:41.800 need a medium for a mechanical wave to to move through. 0:04:41.920 --> 0:04:46.000 But electromagnetic waves are different. They do not require that. 0:04:46.160 --> 0:04:48.600 They can they can propagate through a vacuum. They can 0:04:48.640 --> 0:04:51.800 move through the vacuum space and in fact, they will 0:04:51.880 --> 0:04:58.000 continue to move once generated forever. Really Um, so the 0:04:58.080 --> 0:05:00.440 radio waves that we generated way back when we were 0:05:00.440 --> 0:05:04.600 first figuring this out, they are now, oh well, let's see, 0:05:04.880 --> 0:05:08.039 more than around a hundred light years away, because radio 0:05:08.040 --> 0:05:10.080 waves travel at the speed of light. And then you know, 0:05:10.200 --> 0:05:12.920 the invention of the radio really dates back a century. 0:05:13.720 --> 0:05:17.880 So anything around there, anything generated at that time, would 0:05:18.320 --> 0:05:21.720 now be traveling a hundred light years away. It's kind 0:05:21.720 --> 0:05:25.600 of cool. Yeah, yeah, because it travels the speed of light. Okay, 0:05:25.920 --> 0:05:28.640 so all those all those broadcasts in the forties and 0:05:28.680 --> 0:05:31.640 fifties of the radio cereals, those are now forty fifty 0:05:31.720 --> 0:05:36.440 light years away. Cereal. Um yeah, it's Chris's weakness was 0:05:36.480 --> 0:05:39.320 cereal is like my weakness with pie. So don't don't 0:05:39.360 --> 0:05:41.160 get me wrong. I like the pie. So yeah, I 0:05:41.160 --> 0:05:44.000 mean light and and radio waves are both forms of 0:05:44.080 --> 0:05:48.920 electromagnetic radiation. Um, and it's I had something I was 0:05:48.960 --> 0:05:52.560 gonna say there, I've got something here. So when we 0:05:52.600 --> 0:05:56.080 say electromagnetic that's really important. Now, when you're talking about 0:05:56.080 --> 0:05:59.520 a mechanical wave, you're talking about a wave and a 0:05:59.560 --> 0:06:02.960 particular our alignment. Let's let's say vertical, you know, like 0:06:03.120 --> 0:06:06.680 waves you would see on a notion. Electromagnetic waves are 0:06:06.680 --> 0:06:11.520 actually a pair of waves. There's an electric field wave 0:06:11.640 --> 0:06:13.920 and a magnetic field wave. Now you've heard us talk 0:06:13.960 --> 0:06:17.479 a lot about the relationship between electricity and magnetism and 0:06:17.520 --> 0:06:21.080 how there is this interesting connection between the two. As 0:06:21.080 --> 0:06:24.560 it turns out, if you were to generate an electromagnetic wave, 0:06:25.200 --> 0:06:28.760 you would then have a an electric field wave and 0:06:28.800 --> 0:06:32.000 a magnetic field wave moving at the same time, and 0:06:32.279 --> 0:06:36.640 each one replenishes the other. The electric field, because it's 0:06:36.760 --> 0:06:40.600 changing over time, generates a magnetic field. The magnetic field, 0:06:40.600 --> 0:06:43.719 as it changes over time, regenerates the electric field, and 0:06:43.760 --> 0:06:47.120 that's why it can continue at infinitum out into the 0:06:47.160 --> 0:06:49.240 forest reaches of space until it hits the end of 0:06:49.279 --> 0:06:52.800 the universe. Or we started getting reruns of I Love 0:06:52.880 --> 0:06:58.000 Lucy from you know, a billion light years away. Yeah. 0:06:58.000 --> 0:07:01.480 I remember hearing as a kid that the shows that 0:07:01.560 --> 0:07:05.280 we watched we're going to be available out in space, 0:07:05.320 --> 0:07:08.320 like people in Mars with the right equipment. Of course, 0:07:09.000 --> 0:07:11.320 theoretically there aren't any people on Mars. I don't think 0:07:11.360 --> 0:07:16.840 there are. Um, I wouldn't call them people, yeah, exactly. Um, 0:07:16.920 --> 0:07:18.600 but yeah, if you had a TV and you were 0:07:18.880 --> 0:07:21.000 you know, at that point they said, if you're watching 0:07:21.120 --> 0:07:23.440 from Mars right now you would be catching reruns of 0:07:23.440 --> 0:07:25.800 I Love Lucy. This was years ago, but I was going, 0:07:25.880 --> 0:07:29.080 really seriously, that's that's very cool. So, uh, you know, 0:07:29.120 --> 0:07:31.080 I hadn't realized that they would they would do that. 0:07:31.280 --> 0:07:33.960 But on the same by the same token, if you 0:07:33.960 --> 0:07:37.760 think about the giant radio telescopes that they use UM 0:07:37.960 --> 0:07:41.800 to search for extraterrestrial life, some sign that other people 0:07:41.840 --> 0:07:46.080 are using radio frequencies. Basically they're just listening to space 0:07:46.120 --> 0:07:48.720 to see if there is something. I mean, there's there's lots, 0:07:48.760 --> 0:07:52.040 there's noise. Besides, there's something that is generated in a 0:07:52.640 --> 0:07:56.360 in a meaningful way as opposed to UM, because lots 0:07:56.360 --> 0:08:00.240 of stuff produces radio waves, lots and lots of stuff. Uh. 0:08:00.280 --> 0:08:02.280 And really, like I was saying, so, the the was 0:08:02.280 --> 0:08:04.800 talking about electric field and the magnetic fields that that 0:08:05.240 --> 0:08:10.360 are traveling in this electromagnetic wave. UM. The electric fields 0:08:10.400 --> 0:08:14.920 they exert forces on electric charges, magnetic fields exert forces 0:08:14.960 --> 0:08:19.160 on magnetic polls. So these waves can do work because 0:08:19.200 --> 0:08:24.240 they can exert force upon particular things. In the case 0:08:24.280 --> 0:08:27.560 of the electric field, of course, is the electrically charged particles. 0:08:27.560 --> 0:08:31.640 That's the important part for radios. Without that, without the 0:08:31.640 --> 0:08:34.760 the ability to do work. Radios wouldn't work at all. 0:08:34.480 --> 0:08:37.320 We wouldn't be able to pick these things up. And 0:08:37.520 --> 0:08:41.920 uh so that's really a fundamental element that you have 0:08:41.960 --> 0:08:44.280 to understand before we can get into the mechanical and 0:08:44.440 --> 0:08:49.960 technological elements of radio. Uh and uh so let's talk 0:08:50.000 --> 0:08:52.760 a little bit about how how we get a radio 0:08:52.840 --> 0:08:57.880 signal from a transmitter to a receiver. Alright, so you've 0:08:57.920 --> 0:09:03.319 got a radio station and the radio station you are recording, 0:09:03.480 --> 0:09:06.080 or you're you're trying to broadcast some sort of sound signal. 0:09:07.080 --> 0:09:10.120 You are using a microphone, let's say. So let's say 0:09:10.120 --> 0:09:12.920 this is a talk radio. So there's a guy talking 0:09:12.920 --> 0:09:17.280 into a microphone. Uh. The I can't picture that, right, Yeah, 0:09:17.280 --> 0:09:20.839 it's so hard to understand when you're facing someone doing it. Uh. 0:09:21.160 --> 0:09:24.400 The mechanical waves from the sound of the voice go 0:09:24.559 --> 0:09:27.600 into the microphone. They hit a little diaphragm which then 0:09:28.120 --> 0:09:33.200 uh manipulates an electric charge, creating a frequency within that 0:09:33.240 --> 0:09:37.680 electric charge, which then goes to a I'm simplifying here, 0:09:37.920 --> 0:09:41.520 but but it goes to a transmitter, which then changes 0:09:41.800 --> 0:09:45.880 this electric charge into one of two different um uh 0:09:46.600 --> 0:09:49.199 kinds of radio signals. You've probably heard of a M 0:09:49.240 --> 0:09:53.120 and FM. Yes, well it's not just two, but those 0:09:53.120 --> 0:09:55.520 are the two weeks, those are the two years for broadcast. Yeah, 0:09:55.640 --> 0:09:59.680 for for broadcast radio. Yes, yes, I'm I'm specifically talking 0:09:59.679 --> 0:10:01.560 about the kind of radios where you tune in to 0:10:01.640 --> 0:10:04.360 listen to music or or or talk or whatever. It's 0:10:04.400 --> 0:10:07.120 not I'm not talking citizens band, I'm not talking any 0:10:07.160 --> 0:10:13.040 of the other other kind of UM. Yeah, So, uh, 0:10:13.240 --> 0:10:17.320 the way you you transmit information across those radio waves 0:10:17.440 --> 0:10:20.679 depends on whether you're using a M or FM radio. Right, 0:10:21.040 --> 0:10:24.040 you have to have a carrier wave, which is a 0:10:24.080 --> 0:10:28.120 frequent a radio frequency wave that is able to hold 0:10:28.160 --> 0:10:32.960 information and take it from the transmitter to the receiver. UM. 0:10:33.000 --> 0:10:37.559 And basically it sort of depends on the frequency and amplitude. 0:10:37.760 --> 0:10:40.439 That's that's exactly what a M and FM are. Its 0:10:40.480 --> 0:10:45.400 amplitude modulation and frequency modulation. So with amplitude modulation, you 0:10:45.440 --> 0:10:47.360 remember we were talking about a wave. You know, you 0:10:47.400 --> 0:10:49.959 have the crests the trough, and the from crest to 0:10:50.000 --> 0:10:53.880 crest is wavelength. Well, the the height I guess you 0:10:53.920 --> 0:10:57.080 could say the height of the crests or the depth 0:10:57.160 --> 0:11:00.400 of the trough, which are equivalent in the case of 0:11:00.400 --> 0:11:04.120 these waves. UM. That is the amplitude, right. The bigger 0:11:04.120 --> 0:11:07.760 the amplitude, the the taller those those waves are going 0:11:07.800 --> 0:11:11.240 to look when you look at them as a wavelength. UM. 0:11:11.360 --> 0:11:14.840 So with amplitude modulation, it's exactly what sounds like. You 0:11:14.840 --> 0:11:19.240 you modify the amplitude to contain the uh, the information 0:11:19.280 --> 0:11:23.240 that you're transmitting. When that information is received by a radio, 0:11:23.240 --> 0:11:25.040 I'm gonna skip a little bit here. We're gonna go 0:11:25.120 --> 0:11:27.719 back to the middle section in a minute. But when 0:11:27.760 --> 0:11:31.200 your radio receives an A M signal, it's going to 0:11:31.240 --> 0:11:35.920 detect it's going to detect the the height of those waves. 0:11:36.400 --> 0:11:39.400 And as the height changes over time, that's going to 0:11:39.480 --> 0:11:42.240 give the speaker in your radio the signal to move 0:11:42.320 --> 0:11:45.760 in or out, and your speaker cone technically your speaker 0:11:45.800 --> 0:11:48.000 cone in the speaker. As the speaker cone in your 0:11:48.000 --> 0:11:50.240 speaker moves in and out, that's what generates the sound 0:11:50.280 --> 0:11:54.240 you hear. So as those waves go up and uh 0:11:54.280 --> 0:11:57.480 down in in amplitude uh, and they're gonna be doing 0:11:57.520 --> 0:12:02.920 this uh thousands of of times per second because along 0:12:02.960 --> 0:12:06.280 with the the crest trough and wavelength, you have the frequency. 0:12:06.320 --> 0:12:10.199 The frequency is how many uh, how many cycles, how 0:12:10.200 --> 0:12:13.520 many wavelengths you go through within a second. We call 0:12:13.600 --> 0:12:15.480 that like, if you were to do one cycle a 0:12:15.480 --> 0:12:19.000 second would be one hurts, right, so it kill hurts 0:12:19.080 --> 0:12:22.200 is one thousand cycles in a second. A mega hurts 0:12:22.200 --> 0:12:24.200 would be a million cycles in a second, a giga 0:12:24.240 --> 0:12:27.160 hurts would be a billion cycles in a second. So 0:12:27.559 --> 0:12:31.760 that's a lot. So you're at home. The radio has 0:12:31.840 --> 0:12:35.319 detected the signal and it's detecting the difference in that amplitude, 0:12:35.480 --> 0:12:38.360 and as that amplitude changes over time, that's what tells 0:12:38.400 --> 0:12:41.160 the speaker how to uh to move in and out 0:12:41.160 --> 0:12:44.600 and generate the sound that you hear. Frequency modulation is different. 0:12:45.160 --> 0:12:48.800 The amplitude remains the same, it remains steady h So 0:12:48.880 --> 0:12:51.400 you don't change the amplitude. That's not what tells the 0:12:51.440 --> 0:12:55.240 speaker what the how to interpret that's that's signal to 0:12:55.240 --> 0:12:58.479 turn it into sound. Instead, you you change the frequency 0:12:58.520 --> 0:13:03.920 itself of the transmission, which is a little tricky because 0:13:04.520 --> 0:13:06.520 to tune a radio you have to tune it into 0:13:06.559 --> 0:13:10.520 a specific frequency to to really pick up a good signal. UH. 0:13:10.559 --> 0:13:14.160 So it really generates it keeps it within a fairly 0:13:14.240 --> 0:13:17.080 tight set of parameters. It can't go far beyond that, 0:13:17.200 --> 0:13:18.600 or else you would no longer be able to pick 0:13:18.679 --> 0:13:23.360 up the radio station. But by changing the frequency, that 0:13:23.480 --> 0:13:28.880 is the the number of cycles that UM wavelength goes 0:13:28.920 --> 0:13:32.360 through in a second, that's what tells the speaker how 0:13:32.440 --> 0:13:34.520 to move in and out and generate the sound you hear. 0:13:36.160 --> 0:13:39.760 Now we have to tackle the magical bit in the middle. Okay, 0:13:40.160 --> 0:13:41.880 you know, so we've got you know, you've generated the 0:13:41.880 --> 0:13:44.480 sound and you've heard the sound. But what's happening between 0:13:44.559 --> 0:13:48.280 those two moments and there's some fascinating stuff here, and 0:13:48.320 --> 0:13:51.840 we're gonna get into some science. Uh So, some apologies 0:13:51.920 --> 0:13:55.480 to uh to Robert and Julie who would normally tackle 0:13:55.520 --> 0:13:58.319 this kind of thing, but we're gonna do it. Um. So, 0:13:59.559 --> 0:14:02.800 when you generate that signal at the transmitter, you actually 0:14:02.880 --> 0:14:06.439 create an electric charge that moves up and down your 0:14:06.480 --> 0:14:10.359 transmitter antenna. All right. So antenna are used for two 0:14:10.640 --> 0:14:14.520 main purposes, to transmit signals and to receive signals. Yep. 0:14:14.679 --> 0:14:18.960 And it's true too that, uh the type of frequency 0:14:19.040 --> 0:14:21.960 you're using requires a different type of antenna. For example, 0:14:22.000 --> 0:14:26.040 if you're broadcasting AM versus FM, it requires a different 0:14:26.080 --> 0:14:28.840 antenna length because that has a lot to do with it. 0:14:28.880 --> 0:14:32.240 And and if you've always wondered why, uh, you know, 0:14:32.240 --> 0:14:35.920 I have a clock radio and it's got it basically 0:14:35.920 --> 0:14:38.800 has an internal AM antenna, but it's got an external 0:14:38.840 --> 0:14:40.960 FM antenna. And I didn't understand why until I you know, 0:14:41.000 --> 0:14:42.600 I just really didn't care to look until we were 0:14:42.600 --> 0:14:44.560 deciding to do this. And yeah, it has a lot 0:14:44.640 --> 0:14:48.600 to do with the exactly what we were just talking 0:14:48.640 --> 0:14:51.320 about or what you were just talking about, which is, uh, 0:14:51.560 --> 0:14:54.360 the ways in which they and the carrier wave is 0:14:54.360 --> 0:14:59.320 transmitted in these different technologies, so you know, you need 0:14:59.400 --> 0:15:01.800 a different kind of antenna to transmit and to receive 0:15:02.360 --> 0:15:04.280 those signals depending on what you're trying to do. And 0:15:04.280 --> 0:15:06.920 in general, a general rule of thumb is the best 0:15:06.960 --> 0:15:10.520 antenna to receive a signal is one quarter of the 0:15:10.600 --> 0:15:15.960 length of the radio waves wavelength. But here's the thing. 0:15:16.120 --> 0:15:21.040 AM radio that gets big. I mean AM radio can 0:15:21.080 --> 0:15:25.440 be uh so big. That's larger than a football field. 0:15:25.760 --> 0:15:29.440 And so having an AM radio antenna receiver antenna that's 0:15:29.480 --> 0:15:32.120 a quarter the size of a football field is not 0:15:32.240 --> 0:15:38.520 really on most people's list of home improvement UM projects. 0:15:38.640 --> 0:15:41.720 So there are ways around that, but that's the ideal 0:15:41.840 --> 0:15:48.560 length for a reception antenna. Now, when you when you 0:15:48.600 --> 0:15:52.119 create this electric charge that's going up and down the 0:15:52.120 --> 0:15:55.840 the antenna, you're actually you're using an oscillator to change 0:15:56.000 --> 0:15:59.560 the charge. So you're you're essentially switching the charge. You're 0:15:59.560 --> 0:16:02.920 you're switching voltage on and off up and down this 0:16:02.920 --> 0:16:06.280 this antenna, and that electric charge has it changes over 0:16:06.320 --> 0:16:08.120 time up and down the antenna. That's what creates the 0:16:08.160 --> 0:16:13.400 electromagnetic wave that propagates out from the the transmitter antenna. 0:16:13.760 --> 0:16:17.080 You know, I've watched a lot of movies where um uh, 0:16:17.120 --> 0:16:19.200 you know you've got your giant radio antenna and these 0:16:19.240 --> 0:16:21.640 little electrical things come out the top. You mean that's 0:16:21.640 --> 0:16:25.720 not exactly right. No, you're thinking of our ko Ka 0:16:25.920 --> 0:16:29.160 the old arcade. Yeah, no, you can't see them, although 0:16:29.200 --> 0:16:31.960 it was. Although here's Here's the interesting thing though, is 0:16:31.960 --> 0:16:36.600 that you can pick up you can receive electricity this way, 0:16:36.640 --> 0:16:39.720 although it's a minuscule amount. In fact, that's that's the 0:16:39.760 --> 0:16:42.880 basis of why this ends up working. So you you 0:16:43.160 --> 0:16:45.920 pump lots and lots of electricity into this antenna. We're 0:16:45.920 --> 0:16:49.080 talking about thousands of watts for for an a m station, 0:16:49.840 --> 0:16:54.280 and you are using an oscillator to to move that 0:16:54.840 --> 0:16:57.440 that electric charge up and down the antenna at a 0:16:57.480 --> 0:17:01.040 certain rate. And UH, at that rate depends upon what 0:17:01.160 --> 0:17:03.800 the FCC in the United States has designated as your 0:17:03.840 --> 0:17:07.720 broadcast range. You broadcast your signal that way. Now, let's 0:17:07.760 --> 0:17:13.080 say you want to pick that signal up. The electromagnetic waves, UH, 0:17:13.400 --> 0:17:16.119 move out from that antenna, their directional, they move out 0:17:16.200 --> 0:17:19.760 in every direction really from the antenna. Uh. And then 0:17:20.320 --> 0:17:23.359 you are a certain distance away. You have your radio, 0:17:23.400 --> 0:17:28.000 You've got your antenna extended up. As the electromagnetic waves 0:17:28.600 --> 0:17:32.320 move towards your antenna, your antenna actually can we'll pick 0:17:32.400 --> 0:17:35.760 up a little electrical charge because you've got you know, 0:17:35.800 --> 0:17:40.160 the antenna. That's the whole reason why the radio works 0:17:40.240 --> 0:17:43.680 is that electric field is able to enact the work 0:17:44.160 --> 0:17:46.320 on an electric charge. You've got a little electric charge 0:17:46.320 --> 0:17:50.000 inside that antenna. It alters. But due to this radio wave, 0:17:50.520 --> 0:17:53.840 and assuming that you have your radio tune to the 0:17:53.920 --> 0:17:58.119 right station, UH, what's gonna happen is the electric charge 0:17:58.119 --> 0:18:03.000 in your antenna, your receptor antenna is going to move 0:18:03.080 --> 0:18:05.320 up and down a certain frequency. If you have tuned 0:18:05.359 --> 0:18:08.280 your radio properly, it's going to be at the circuit 0:18:08.320 --> 0:18:11.080 in your radio is gonna be at a resonant frequency 0:18:11.240 --> 0:18:14.920 with that charge that's moving up and down in your antenna. Now, 0:18:14.920 --> 0:18:19.240 if you've heard about resonant frequencies, that's when you can 0:18:19.760 --> 0:18:25.040 uh make something essentially vibrate at uh an ideal frequency 0:18:25.320 --> 0:18:29.800 for stuff to go crazy like we we've seen. You know, 0:18:29.920 --> 0:18:32.000 you might have seen a MythBusters episode where they started 0:18:32.000 --> 0:18:34.640 talking about resonant frequencies. Yes, the idea being that us 0:18:34.880 --> 0:18:39.440 should wind blow across a bridge at a particular frequency 0:18:39.760 --> 0:18:43.560 of a particular speed. It would create this uh, this 0:18:44.359 --> 0:18:47.720 sort of uh vicious cycle that feeds into itself where 0:18:47.720 --> 0:18:51.400 the bridge itself starts to shake apart. Well, resonant frequencies 0:18:51.480 --> 0:18:54.520 are a real thing, and if you do generate uh 0:18:54.680 --> 0:18:58.280 the right resonant frequency, you can create a larger and 0:18:58.400 --> 0:19:03.199 larger um uh vibrations in a medium. So think of 0:19:03.240 --> 0:19:05.119 it kind of like you've got a kid on a 0:19:05.240 --> 0:19:08.560 swing and you're pushing the kid on the swing. If 0:19:08.560 --> 0:19:10.240 you push the kid at just the right time, the 0:19:10.320 --> 0:19:14.120 kid's gonna go up higher each on each swing, Right, 0:19:14.480 --> 0:19:17.120 You're you're adding more energy into it, and it's and 0:19:17.320 --> 0:19:20.520 uh you see the output as the kid goes up higher. 0:19:20.680 --> 0:19:23.320 If you push it the wrong time, the kid just 0:19:23.400 --> 0:19:25.680 ends up drinking around and falling off the swing set 0:19:25.720 --> 0:19:31.280 and crying like like I did. Thanks Dad. Anyway, uh So, 0:19:32.200 --> 0:19:35.239 the the circuit in your radio, when you tune it, 0:19:35.320 --> 0:19:37.800 you actually alter the circuit a little bit so that 0:19:38.040 --> 0:19:40.640 it will resonate at a different frequency once it hits 0:19:40.640 --> 0:19:43.240 the right frequency for the radio wave that's hitting your antenna. 0:19:43.720 --> 0:19:46.960 Those little uh the electric charge is going up and 0:19:46.960 --> 0:19:51.600 down your your antenna will cause a larger reaction within 0:19:51.720 --> 0:19:54.720 the circuit in your radio, which is what you're is 0:19:55.119 --> 0:19:58.400 picked up by the amplifier and then converted into um 0:19:58.480 --> 0:20:04.640 sound through your speaker. Yeah. Yeah, So should we get 0:20:04.640 --> 0:20:07.560 into some of the other cool stuff? Yeah, like hit 0:20:07.600 --> 0:20:10.960 me with stereo. Oh man, I didn't even go into stereo. 0:20:11.040 --> 0:20:13.600 I was. I was so concentrated on I want to 0:20:13.640 --> 0:20:16.119 make sure I can explain the science of how this 0:20:16.240 --> 0:20:19.520 radio wave moves across. Um. It's actually really fascinating stuff. 0:20:19.560 --> 0:20:21.200 And all, you know what we should do before we 0:20:21.240 --> 0:20:25.720 talk about stereo. Crystal radio. Okay, that's the simplest kind 0:20:25.720 --> 0:20:28.440 of radio I can think of. As a matter of fact. Um, 0:20:28.520 --> 0:20:30.480 when I was a kid, I had I probably still 0:20:30.520 --> 0:20:34.080 do in the box somewhere a crystal radio kit. UM. 0:20:34.119 --> 0:20:35.800 And yeah, when I was when I was doing a 0:20:35.800 --> 0:20:40.080 little research. UM, one of the things that really lead 0:20:40.160 --> 0:20:45.840 to radio being functional was UM the ability to when 0:20:45.840 --> 0:20:48.760 they discovered the ability to tune a radio. It's like 0:20:48.800 --> 0:20:51.480 I I don't want to just search for whatever. I 0:20:51.480 --> 0:20:53.800 want to be able to lock it in to to 0:20:53.960 --> 0:20:58.440 detect a specific UH signal. And and when they developed 0:20:58.440 --> 0:21:01.879 the ability to tune a radio, that basically made UM 0:21:02.000 --> 0:21:05.200 what is what is now the radio industry possible because 0:21:05.240 --> 0:21:08.320 you can tune into a specific UH station and leave 0:21:08.400 --> 0:21:11.320 it there and it's not going anywhere. UM. Of course, 0:21:11.520 --> 0:21:14.560 you have to be very careful, especially if you're the 0:21:14.560 --> 0:21:18.240 the licensing group. UM. Here in Atlanta there are tons 0:21:18.240 --> 0:21:20.320 and tons of radio stations. And I had this problem 0:21:20.320 --> 0:21:26.240 with UM. UM. I had an iPod with a broadcaster 0:21:26.359 --> 0:21:28.560 that I used to use trying to play through my 0:21:28.720 --> 0:21:31.119 radio rather than you know, hooking it up in some 0:21:31.160 --> 0:21:34.159 way physically with a tape adapter or a plug or 0:21:34.160 --> 0:21:36.879 something like that. And UH, you know, you have to 0:21:36.920 --> 0:21:41.679 have a certain distance between stations for the signal not 0:21:41.760 --> 0:21:43.800 to for the carrier waves not to bleed over and 0:21:43.800 --> 0:21:47.160 and basically muddle the information in between. And I had 0:21:47.640 --> 0:21:49.840 as I would drive around Atlanta, I would have to 0:21:49.920 --> 0:21:54.479 change the station that my iPod broadcaster was broadcasting on 0:21:54.560 --> 0:21:57.959 because um, you know, I would start to enter another 0:21:58.000 --> 0:22:00.600 station more powerful signal would start to interfere with it, 0:22:00.600 --> 0:22:03.840 and I would have to to do that. UM. So yeah, 0:22:03.920 --> 0:22:09.680 this the crystal set that's really really basic. UM. In fact, 0:22:09.720 --> 0:22:12.399 the one I got from radio Shack was basically, uh, 0:22:12.440 --> 0:22:14.679 it was already hooked up, so to speak. It had 0:22:14.720 --> 0:22:17.359 It was one of those that has the springs and 0:22:17.400 --> 0:22:20.600 you you connect the wires using the springs. And if 0:22:20.600 --> 0:22:23.639 you haven't seen these kits, um, you know, basic electronics 0:22:23.640 --> 0:22:26.560 type kits. There's a h the board is wired underneath 0:22:26.840 --> 0:22:31.159 and there are very tight, tightly coiled springs installed in 0:22:31.240 --> 0:22:33.920 the top. And to make a connection from one point 0:22:33.960 --> 0:22:36.320 to the other to finish your kit build the radio. 0:22:36.359 --> 0:22:39.600 In this case, UM, you have wires that are um 0:22:40.160 --> 0:22:42.800 uh not insulated on the very ends and you bend 0:22:42.880 --> 0:22:45.240 the spring stick the end of the metal end of 0:22:45.240 --> 0:22:47.359 the wire and let go and the spring holds it 0:22:47.400 --> 0:22:50.399 into place. UM. And with that, you know, and I 0:22:50.440 --> 0:22:51.959 had a long wire that I would use to pick 0:22:52.040 --> 0:22:54.840 up a M signals. That would be your antenna. The antenna. 0:22:55.640 --> 0:22:58.000 But yeah, if you're you know, if you don't know 0:22:58.040 --> 0:23:00.199 what's going on, it looks sort of a lot the 0:23:00.280 --> 0:23:02.159 other wires in the kit, but you know, you'd have 0:23:02.200 --> 0:23:04.439 to extend it away, and and a small knob that 0:23:04.480 --> 0:23:06.600 you would use to tune that. But it also had 0:23:06.920 --> 0:23:10.920 a coil of metal. It looked like electromagnet. Yeah, I 0:23:10.960 --> 0:23:13.400 can actually talk a little bit about that. There are 0:23:13.440 --> 0:23:17.080 four basic components of a crystal radio. These are These 0:23:17.119 --> 0:23:19.480 are literally the only four things you need to make 0:23:19.600 --> 0:23:25.720 the most basic a M radio. You need an antenna, 0:23:25.760 --> 0:23:27.800