1 00:00:04,160 --> 00:00:07,160 Speaker 1: Get in text with technology with tech Stuff from how 2 00:00:07,240 --> 00:00:13,840 Speaker 1: stuff Works dot com. Hey there, and welcome to tech Stuff. 3 00:00:13,880 --> 00:00:17,600 Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer at 4 00:00:17,600 --> 00:00:21,160 Speaker 1: how Stuff Works in a love all things tech, and 5 00:00:21,239 --> 00:00:25,040 Speaker 1: today we're going to talk about radar, the history of radar, 6 00:00:25,120 --> 00:00:27,360 Speaker 1: how it works, that kind of stuff. This comes to 7 00:00:27,440 --> 00:00:32,320 Speaker 1: us courtesy of some listener requests. Actually two different listeners, 8 00:00:32,440 --> 00:00:36,120 Speaker 1: Scott and Doug both asked about this. Doug specifically was 9 00:00:36,159 --> 00:00:39,800 Speaker 1: curious about radar guns. But the technology is pretty simple 10 00:00:39,840 --> 00:00:43,600 Speaker 1: once you know the the underlying principles. So I'm gonna 11 00:00:43,800 --> 00:00:46,000 Speaker 1: lump them all together here. Plus I've talked a lot 12 00:00:46,040 --> 00:00:50,279 Speaker 1: about radar recently, with topics on folks like Alfred Lee 13 00:00:50,320 --> 00:00:54,600 Speaker 1: Loomis and his Loran navigation system, so a lot of 14 00:00:54,600 --> 00:00:57,160 Speaker 1: that's going to tie in here as well. Now, to 15 00:00:57,240 --> 00:01:01,080 Speaker 1: begin with, in order to understand radar and all the 16 00:01:01,160 --> 00:01:04,720 Speaker 1: different principles behind it, we have to look back to 17 00:01:04,800 --> 00:01:08,440 Speaker 1: the nineteenth century, all the way back in eighteen forty two. 18 00:01:08,840 --> 00:01:13,119 Speaker 1: And no, we weren't using radar in eighteen forty two. 19 00:01:13,520 --> 00:01:17,440 Speaker 1: He didn't have a bunch of nineteenth century military officials 20 00:01:17,440 --> 00:01:19,600 Speaker 1: trying to figure out where the next wooden boat was. 21 00:01:20,360 --> 00:01:24,000 Speaker 1: But in eighteen forty two, an Austrian physicist and astronomer 22 00:01:24,080 --> 00:01:29,520 Speaker 1: named Christian Johann Doppler published a paper on the determination 23 00:01:29,720 --> 00:01:33,280 Speaker 1: of motion using the frequency of light in the study 24 00:01:33,400 --> 00:01:36,679 Speaker 1: of the movement of stars, and this became known as 25 00:01:36,720 --> 00:01:40,760 Speaker 1: the Doppler principle. And here's what he was talking about. So, 26 00:01:41,000 --> 00:01:45,160 Speaker 1: light is a type of electro magnetic radiation as part 27 00:01:45,160 --> 00:01:48,880 Speaker 1: of the electromagnetic spectrum. You can measure light in waves, 28 00:01:49,280 --> 00:01:51,920 Speaker 1: though light can also behave as a particle, but let's 29 00:01:51,920 --> 00:01:54,360 Speaker 1: put that aside for an How we're specifically talking about 30 00:01:54,440 --> 00:01:57,960 Speaker 1: light in its nature as a wave, and waves have 31 00:01:58,120 --> 00:02:02,320 Speaker 1: a wave length. That is where you can measure from 32 00:02:02,360 --> 00:02:05,440 Speaker 1: one point on a wave to the next point that 33 00:02:05,600 --> 00:02:08,360 Speaker 1: is the exact same sort of point further down the wavelength. 34 00:02:08,400 --> 00:02:11,360 Speaker 1: That's the wavelength. So like the crest, if you go 35 00:02:11,440 --> 00:02:14,480 Speaker 1: to the very peak and you measure to the next peak, 36 00:02:15,000 --> 00:02:18,320 Speaker 1: that would be one wavelength of that wave. Visible light 37 00:02:18,360 --> 00:02:22,440 Speaker 1: has a very very small wavelength. The visible light spectrum 38 00:02:22,520 --> 00:02:26,919 Speaker 1: ranges from around three nine nanometers to seven hundred nanometers, 39 00:02:26,960 --> 00:02:30,080 Speaker 1: and a nanometer is one billionth of a meter, so 40 00:02:31,080 --> 00:02:35,280 Speaker 1: very very tiny wavelengths. Now, do you remember your pneumonic 41 00:02:35,320 --> 00:02:38,720 Speaker 1: device for the color spectrum, You know, the roy G BIV, 42 00:02:39,160 --> 00:02:42,720 Speaker 1: which stands for red, orange, yellow, green, blue, indigo, violet. 43 00:02:43,360 --> 00:02:46,280 Speaker 1: That's not just the spectrum, that's not just the colors 44 00:02:46,280 --> 00:02:51,080 Speaker 1: of a rainbow. Those colors actually represent wavelengths of descending length. 45 00:02:51,560 --> 00:02:55,120 Speaker 1: So red light has the longest wavelength invisible light, and 46 00:02:55,240 --> 00:02:59,799 Speaker 1: violet the shortest wavelength invisible light. All light travels at 47 00:02:59,840 --> 00:03:04,160 Speaker 1: the same speed, which here you go, mind blowing fact. 48 00:03:04,200 --> 00:03:06,799 Speaker 1: Here that's the speed of light. Now, keep in mind 49 00:03:06,840 --> 00:03:09,920 Speaker 1: the speed of light actually changes somewhat depending upon the 50 00:03:09,960 --> 00:03:12,560 Speaker 1: medium it passes through. When we typically say the speed 51 00:03:12,560 --> 00:03:15,799 Speaker 1: of light, we usually mean through a vacuum, But speed 52 00:03:15,800 --> 00:03:18,600 Speaker 1: of light through air is slightly slower because it's moving 53 00:03:18,639 --> 00:03:22,440 Speaker 1: through a different medium. When I say slightly slower, I 54 00:03:22,480 --> 00:03:27,520 Speaker 1: mean incredibly incredibly tiny difference for us, Like, it's still 55 00:03:28,040 --> 00:03:32,760 Speaker 1: wicked fast. So all light travels at that speed. Really, 56 00:03:32,800 --> 00:03:36,800 Speaker 1: all electromagnetic radiation travels at that speed. But this also 57 00:03:36,880 --> 00:03:40,600 Speaker 1: means that shorter wavelengths of light have a higher frequency, 58 00:03:40,920 --> 00:03:44,000 Speaker 1: meaning you have more instances of a wave pass a 59 00:03:44,080 --> 00:03:47,720 Speaker 1: specific point within a specific amount of time. Because the 60 00:03:47,760 --> 00:03:50,360 Speaker 1: waves are shorter, but they're moving at the same speed 61 00:03:50,400 --> 00:03:53,760 Speaker 1: as the longer waves. Now, I used an analogy recently 62 00:03:54,320 --> 00:03:57,960 Speaker 1: of a highway with cars on it. So just imagine 63 00:03:57,960 --> 00:03:59,920 Speaker 1: you're standing on the side of this highway and all 64 00:04:00,120 --> 00:04:03,800 Speaker 1: the cars are traveling at the same speed. Now, first, 65 00:04:04,160 --> 00:04:06,800 Speaker 1: let's say that there are a there's a row of 66 00:04:06,800 --> 00:04:09,440 Speaker 1: buses and they're just passing you, and they're all traveling 67 00:04:09,480 --> 00:04:13,320 Speaker 1: at this particular speed, and for the purposes of this example, 68 00:04:13,360 --> 00:04:16,560 Speaker 1: we'll just say it's fifty miles per hour. They're equally spaced, 69 00:04:16,720 --> 00:04:21,000 Speaker 1: just inches apart from each other, so it's incredibly dangerous, 70 00:04:21,040 --> 00:04:23,640 Speaker 1: but they're all moving at this fifty miles per hour 71 00:04:23,720 --> 00:04:27,320 Speaker 1: speed and they're passing you. Next, imagine that there is 72 00:04:27,360 --> 00:04:30,200 Speaker 1: a row of tiny smart cars that are passing you. 73 00:04:30,320 --> 00:04:33,479 Speaker 1: These are also inches apart from each other, so uh, 74 00:04:33,520 --> 00:04:35,960 Speaker 1: they are very close together, and they're traveling at the 75 00:04:36,000 --> 00:04:38,600 Speaker 1: same speed the buses were. Earlier, they're also traveling at 76 00:04:38,640 --> 00:04:41,919 Speaker 1: fifty miles per hour. You'll have more smart cars pass 77 00:04:42,000 --> 00:04:45,400 Speaker 1: you by in that same amount of time because they're smaller. 78 00:04:45,720 --> 00:04:47,880 Speaker 1: They're traveling at the same speed as the buses, but 79 00:04:48,000 --> 00:04:50,360 Speaker 1: they have less lengths, so you get more of them. 80 00:04:50,400 --> 00:04:53,120 Speaker 1: In in the same amount of time. Same thing is 81 00:04:53,160 --> 00:04:58,880 Speaker 1: true with frequencies electromagnetic frequencies. Uh, light is the same thing. 82 00:04:58,920 --> 00:05:01,039 Speaker 1: All light is traveling at the same speed, but shorter 83 00:05:01,120 --> 00:05:03,479 Speaker 1: wavelengths mean that you have a higher frequency, a higher 84 00:05:03,560 --> 00:05:07,240 Speaker 1: number of waves passing through a certain point at a 85 00:05:07,240 --> 00:05:10,120 Speaker 1: certain a certain amount of time. So what exactly was 86 00:05:10,160 --> 00:05:13,039 Speaker 1: Doppler saying. Well, he was talking about how you could 87 00:05:13,080 --> 00:05:16,880 Speaker 1: tell whether stars were moving toward or away from the 88 00:05:16,960 --> 00:05:20,279 Speaker 1: viewer by the wavelength of light that you observed when 89 00:05:20,279 --> 00:05:23,839 Speaker 1: looking at the star. A body moving away from the 90 00:05:23,920 --> 00:05:27,719 Speaker 1: viewer would have elongated waves, almost as if it were 91 00:05:27,760 --> 00:05:31,600 Speaker 1: stretching out the light behind it, So it would be 92 00:05:31,680 --> 00:05:35,000 Speaker 1: a red shift because you'd be shifting closer towards the 93 00:05:35,040 --> 00:05:37,920 Speaker 1: red side of the spectrum. Uh, that's the side of 94 00:05:37,920 --> 00:05:41,080 Speaker 1: the spectrum that has the longer wavelengths. So something moving 95 00:05:41,120 --> 00:05:44,479 Speaker 1: away from you with these elongated wavelengths would be red shifted. 96 00:05:44,640 --> 00:05:48,520 Speaker 1: But if a star were moving toward you, then it 97 00:05:48,560 --> 00:05:51,880 Speaker 1: would have compressed waves of light pushed ahead of it, 98 00:05:52,320 --> 00:05:55,520 Speaker 1: so you would have the more of these wavelengths pushed 99 00:05:55,520 --> 00:05:58,680 Speaker 1: towards you would be scrunched up. This would be blue 100 00:05:58,720 --> 00:06:02,200 Speaker 1: shifted toward you. And we call this the Doppler effect, 101 00:06:02,240 --> 00:06:05,240 Speaker 1: and it would become really important in radar, and it's 102 00:06:05,240 --> 00:06:08,080 Speaker 1: also something that we can observe in our regular lives. 103 00:06:08,080 --> 00:06:10,960 Speaker 1: We don't have to have a powerful telescope or a 104 00:06:11,360 --> 00:06:14,200 Speaker 1: spectroscope to be able to do this because it works 105 00:06:14,200 --> 00:06:16,880 Speaker 1: with lots of different kinds of waves, not just electro 106 00:06:16,960 --> 00:06:20,640 Speaker 1: magnetic waves. It also works with sound waves. If you've 107 00:06:20,680 --> 00:06:24,000 Speaker 1: ever heard a vehicle with a siren coming toward you, 108 00:06:24,000 --> 00:06:26,000 Speaker 1: you might have noticed that it has a higher pitch 109 00:06:26,120 --> 00:06:29,680 Speaker 1: sound as it approaches you, and then after it passes you, 110 00:06:29,760 --> 00:06:33,240 Speaker 1: the pitch on the siren goes down as the vehicles 111 00:06:33,279 --> 00:06:36,479 Speaker 1: moving away. This is the Doppler effect, in which the 112 00:06:36,520 --> 00:06:39,960 Speaker 1: sound waves are compressed as the vehicle is coming towards you, 113 00:06:40,560 --> 00:06:44,480 Speaker 1: and they are elongated as the vehicles moving away from you. 114 00:06:44,480 --> 00:06:46,960 Speaker 1: And the vehicle we're staying perfectly still, you would hear 115 00:06:47,000 --> 00:06:51,279 Speaker 1: a pitch somewhere in between those two other pitches. Also, 116 00:06:51,400 --> 00:06:53,520 Speaker 1: if you're going faster than the speed of sound, if 117 00:06:53,600 --> 00:06:57,560 Speaker 1: you your vehicles traveling faster than sound itself can travel, 118 00:06:57,800 --> 00:07:00,679 Speaker 1: you would create what's called a sonic boom. But that's 119 00:07:00,800 --> 00:07:05,520 Speaker 1: beside the point. So Smarty Pants Doppler observes this phenomena, 120 00:07:05,600 --> 00:07:08,440 Speaker 1: which would allow future engineers a chance to determine if 121 00:07:08,480 --> 00:07:11,160 Speaker 1: something was coming toward them or moving away from them 122 00:07:11,200 --> 00:07:14,560 Speaker 1: based off of radar. It would take nearly a century 123 00:07:14,600 --> 00:07:17,840 Speaker 1: for that to pay off in that way. However, The 124 00:07:17,880 --> 00:07:21,920 Speaker 1: next person I need to talk about briefly is Heinrich Hurtz, 125 00:07:22,080 --> 00:07:26,040 Speaker 1: who was a German physicist who conducted numerous experiments in 126 00:07:26,080 --> 00:07:30,560 Speaker 1: the late nineteenth century around the eighteen eighties, and Hurts 127 00:07:30,600 --> 00:07:33,120 Speaker 1: has a familiar name if you have talked a lot 128 00:07:33,120 --> 00:07:37,440 Speaker 1: about frequencies. Hurts, in turn was building off of theoretical 129 00:07:37,480 --> 00:07:41,520 Speaker 1: work that was done by a Scottish physicist named James 130 00:07:41,600 --> 00:07:45,280 Speaker 1: Clerk Maxwell. So Maxwell had this idea. He had a 131 00:07:45,360 --> 00:07:48,840 Speaker 1: theory that light and radio waves were all part of 132 00:07:48,880 --> 00:07:52,440 Speaker 1: a larger spectrum of waves, so effectively this would be 133 00:07:52,440 --> 00:07:56,000 Speaker 1: the electro magnetic spectrum, and that all of these waves 134 00:07:56,000 --> 00:07:59,800 Speaker 1: would follow the same fundamental rules. Though the waves of 135 00:08:00,000 --> 00:08:03,160 Speaker 1: cells would have a have very different wavelengths and frequencies, 136 00:08:03,480 --> 00:08:07,920 Speaker 1: so the specific reactions will be a little different based 137 00:08:08,000 --> 00:08:10,640 Speaker 1: upon the wavelengths and frequencies involved, but they would all 138 00:08:10,680 --> 00:08:14,480 Speaker 1: follow the same basic set of rules. Maxwell's work suggested 139 00:08:14,520 --> 00:08:19,160 Speaker 1: that radio waves could be reflected off of metallic surfaces 140 00:08:19,200 --> 00:08:21,880 Speaker 1: just as light. Could you know if you have a mirror, 141 00:08:21,920 --> 00:08:24,240 Speaker 1: you can bounce light around. Well, he said, well, if 142 00:08:24,240 --> 00:08:27,080 Speaker 1: that's the case, if light behaves this way, and if 143 00:08:27,080 --> 00:08:31,120 Speaker 1: electromagnetic radiation also behaves in that way, then you would 144 00:08:31,120 --> 00:08:35,160 Speaker 1: expect electromagnetic radiation to also bounce off these surfaces. We 145 00:08:35,240 --> 00:08:37,840 Speaker 1: can't see it, but it should still happen because they 146 00:08:37,840 --> 00:08:41,080 Speaker 1: should still follow those rules. So Hurts set out to 147 00:08:41,200 --> 00:08:45,760 Speaker 1: test that theory through experimentation, and he used radio waves 148 00:08:45,760 --> 00:08:48,960 Speaker 1: that are frequency of about four hundred fifty five mega hurts, 149 00:08:49,000 --> 00:08:52,840 Speaker 1: which meant the wavelengths were about sixty six centimeters in length. 150 00:08:53,320 --> 00:08:57,840 Speaker 1: And he found in eight eight that Maxwell's theories held merit. 151 00:08:57,920 --> 00:09:01,800 Speaker 1: They did a seemed to follow those fundamental rules. So 152 00:09:01,840 --> 00:09:03,960 Speaker 1: in nineteen o four we then have to talk about 153 00:09:04,000 --> 00:09:08,120 Speaker 1: a German engineer named Christian Hulsmeyer who applied for a 154 00:09:08,160 --> 00:09:11,840 Speaker 1: patent for a quote an obstacle detector and ship navigation 155 00:09:11,880 --> 00:09:15,200 Speaker 1: device end quote based off of this principle. This would 156 00:09:15,200 --> 00:09:18,280 Speaker 1: have been a very early form of radar, but at 157 00:09:18,280 --> 00:09:21,400 Speaker 1: the time no one was terribly interested in it, as 158 00:09:21,440 --> 00:09:24,800 Speaker 1: there was no real practical use for it, yet not 159 00:09:24,920 --> 00:09:28,920 Speaker 1: in nineteen o four. Uh. It would later become extremely practical, 160 00:09:28,960 --> 00:09:32,079 Speaker 1: but no one could foresee that at the time. Skip 161 00:09:32,080 --> 00:09:36,160 Speaker 1: ahead several decades after the development of radio, geniuses like 162 00:09:36,200 --> 00:09:39,640 Speaker 1: Tesla and Marconi had advanced our understanding of radio waves 163 00:09:39,640 --> 00:09:42,640 Speaker 1: and how to generate them, and by the nineteen thirties 164 00:09:43,000 --> 00:09:46,040 Speaker 1: radio was widely deployed in many parts of the world. 165 00:09:46,400 --> 00:09:49,880 Speaker 1: But engineers noticed something interesting. They saw that when you 166 00:09:49,960 --> 00:09:54,360 Speaker 1: had transmitters posted across bodies of water, sometimes radio waves 167 00:09:54,400 --> 00:09:58,400 Speaker 1: from one transmitter would bounce back to that source transmitter. 168 00:09:58,840 --> 00:10:03,080 Speaker 1: It corresponded with ups passing between the two transmitters. The 169 00:10:03,120 --> 00:10:06,520 Speaker 1: engineers and scientists observing this theorized that what must be 170 00:10:06,600 --> 00:10:09,440 Speaker 1: happening is that some of those radio waves were going 171 00:10:09,480 --> 00:10:12,679 Speaker 1: out over the water, colliding with a shop, and then 172 00:10:12,720 --> 00:10:15,720 Speaker 1: bouncing back to the source. They were noticing the same 173 00:10:15,760 --> 00:10:19,840 Speaker 1: effects that Hurts had tested decades earlier. But how would 174 00:10:19,840 --> 00:10:23,200 Speaker 1: they make it a practical technology. Well, many different nations 175 00:10:23,240 --> 00:10:27,719 Speaker 1: explored the possibility of using radio to detect large objects. 176 00:10:28,080 --> 00:10:31,079 Speaker 1: In ninety two, in the United States, the United States 177 00:10:31,240 --> 00:10:35,800 Speaker 1: Naval Research Laboratory in Washington, d C. Noted fluctuations in 178 00:10:35,960 --> 00:10:39,400 Speaker 1: radio signal intensity between a transmitter on one side of 179 00:10:39,440 --> 00:10:42,440 Speaker 1: the Potomac River and a receiver on the other side 180 00:10:42,440 --> 00:10:45,600 Speaker 1: of the river. The fluctuations only occurred when a ship 181 00:10:45,679 --> 00:10:48,560 Speaker 1: passed between the transmitter and the receiver on the river. 182 00:10:49,200 --> 00:10:52,160 Speaker 1: But the upper levels of the Navy weren't interested in 183 00:10:52,200 --> 00:10:54,880 Speaker 1: the technology as it stood, and it was only after 184 00:10:54,920 --> 00:10:58,280 Speaker 1: the development of monostatic radar and which you used the 185 00:10:58,280 --> 00:11:02,160 Speaker 1: exact same antenna as a transmitter and a receiver, that 186 00:11:02,240 --> 00:11:05,520 Speaker 1: the Navy began to fund serious research and development. And 187 00:11:05,600 --> 00:11:09,720 Speaker 1: that wouldn't happen until nineteen thirty nine. Enter Sir Robert 188 00:11:09,720 --> 00:11:15,400 Speaker 1: Alexander Watson what a Scottish physicist. Now he is frequently 189 00:11:15,440 --> 00:11:18,480 Speaker 1: credited as quote unquote the inventor of radar, but I 190 00:11:18,520 --> 00:11:21,360 Speaker 1: need to say there were an awful lot of people, 191 00:11:21,520 --> 00:11:25,040 Speaker 1: all working on similar ideas at the same time, so 192 00:11:25,120 --> 00:11:27,680 Speaker 1: it's very difficult. In fact, it's impossible to say one 193 00:11:27,760 --> 00:11:31,280 Speaker 1: person was the inventor of radar. One person tends to 194 00:11:31,320 --> 00:11:33,000 Speaker 1: get the credit for it, but in fact this was 195 00:11:33,040 --> 00:11:38,560 Speaker 1: happening all around the world simultaneously. So uh Watson what 196 00:11:38,840 --> 00:11:41,960 Speaker 1: was born in eighteen ninety two. He attended the University 197 00:11:42,000 --> 00:11:44,600 Speaker 1: of St Andrews, and he had begun his scientific career 198 00:11:45,000 --> 00:11:48,719 Speaker 1: as sort of a meteorologist uh timpting to develop technology 199 00:11:48,760 --> 00:11:52,000 Speaker 1: that could detect and track thunderstorms. He had observed this 200 00:11:52,040 --> 00:11:56,160 Speaker 1: phenomenon of radio waves reflected off of things like ships, 201 00:11:56,480 --> 00:11:58,920 Speaker 1: and wrote a memorandum to the British government in nineteen 202 00:11:59,000 --> 00:12:02,360 Speaker 1: thirty five. It was his opinion that given a radio 203 00:12:02,440 --> 00:12:06,320 Speaker 1: transmitter and a receiver, with sufficient power and radio waves 204 00:12:06,320 --> 00:12:10,679 Speaker 1: in the proper frequency, you could potentially detect incoming aircraft, 205 00:12:10,960 --> 00:12:13,480 Speaker 1: and such a device would be an incredibly powerful tool, 206 00:12:13,840 --> 00:12:16,679 Speaker 1: not just in peace time, but also in war, and 207 00:12:16,880 --> 00:12:20,480 Speaker 1: tensions were mounting in Europe in nineteen thirty five, so 208 00:12:20,520 --> 00:12:23,920 Speaker 1: this was a high priority. Being able to detect an 209 00:12:23,960 --> 00:12:27,719 Speaker 1: incoming air attack could save thousands of lives. And I'll 210 00:12:27,760 --> 00:12:30,000 Speaker 1: talk more about what he did in just a second, 211 00:12:30,080 --> 00:12:32,920 Speaker 1: but first let's take a quick break to thank our 212 00:12:33,000 --> 00:12:44,200 Speaker 1: sponsor Watson what began to experiment with a design for 213 00:12:44,280 --> 00:12:48,120 Speaker 1: detecting aircraft in ninety five. He developed a transmitter and 214 00:12:48,160 --> 00:12:51,480 Speaker 1: a receiver and was using it to locate any sort 215 00:12:51,520 --> 00:12:54,520 Speaker 1: of aircraft from a distance of about ninety miles or 216 00:12:56,600 --> 00:12:59,360 Speaker 1: His work inspired the British government to fund a project 217 00:12:59,480 --> 00:13:03,240 Speaker 1: called chain Home, which was a system of radars that 218 00:13:03,360 --> 00:13:07,959 Speaker 1: operated on frequencies ranging from twenty two to fifty mega hurts. Now, 219 00:13:08,040 --> 00:13:10,960 Speaker 1: visible light is in the four dred thirty to seven 220 00:13:11,400 --> 00:13:15,839 Speaker 1: seventy terror hurts range. So how long were the wavelengths 221 00:13:15,880 --> 00:13:19,240 Speaker 1: that Watson What was working with? While they ranged from 222 00:13:19,280 --> 00:13:23,080 Speaker 1: about six meters or nineteen point seven ft to thirteen 223 00:13:23,160 --> 00:13:26,200 Speaker 1: point six meters or forty four point seven feet, So 224 00:13:26,559 --> 00:13:29,600 Speaker 1: these were waves that were on many orders of magnitude 225 00:13:29,640 --> 00:13:33,960 Speaker 1: longer than the nanometer scale wavelengths of visible light. They 226 00:13:33,960 --> 00:13:38,480 Speaker 1: were huge in comparison. Watson What said that the use 227 00:13:38,520 --> 00:13:41,719 Speaker 1: of such long wavelengths followed a philosophy he called the 228 00:13:41,800 --> 00:13:46,160 Speaker 1: cult of the imperfect. He defined this as quote, give 229 00:13:46,200 --> 00:13:49,480 Speaker 1: them the third best to go on with, the second 230 00:13:49,480 --> 00:13:53,400 Speaker 1: best comes too late, the best never comes end quote. 231 00:13:53,559 --> 00:13:56,280 Speaker 1: So in other words, he says, yeah, we could have 232 00:13:56,320 --> 00:14:00,840 Speaker 1: tried to generate smaller wavelengths, which would have solved a 233 00:14:00,880 --> 00:14:02,720 Speaker 1: lot of problems. One, it would have given you better 234 00:14:02,720 --> 00:14:06,800 Speaker 1: resolution to It would have cut down on noise and interference, 235 00:14:07,360 --> 00:14:10,360 Speaker 1: but it also would have taken longer to develop. If 236 00:14:10,360 --> 00:14:12,800 Speaker 1: you want something that you can deploy, you go with 237 00:14:12,880 --> 00:14:15,839 Speaker 1: an easier solution, you have to set that goal lower 238 00:14:15,880 --> 00:14:18,320 Speaker 1: than what you want in order to deliver on time 239 00:14:18,480 --> 00:14:23,080 Speaker 1: if timeliness is more important than resolution. For example, the 240 00:14:23,200 --> 00:14:26,920 Speaker 1: chain home system went online in September night as a 241 00:14:27,000 --> 00:14:31,040 Speaker 1: twenty four hour detection system. The system helped England detect 242 00:14:31,160 --> 00:14:34,840 Speaker 1: incoming bombing runs from the Germans and melt a limited 243 00:14:34,880 --> 00:14:38,480 Speaker 1: air defense with their own capabilities, and without that system, 244 00:14:38,520 --> 00:14:41,080 Speaker 1: the damage and losses from German attacks would have been 245 00:14:41,160 --> 00:14:44,400 Speaker 1: much greater than what they were. Other nations such as 246 00:14:44,440 --> 00:14:48,280 Speaker 1: the Soviet Union, Germany, Japan, the United States, and many 247 00:14:48,320 --> 00:14:52,280 Speaker 1: others were all working on similar radar technologies around this time, 248 00:14:52,600 --> 00:14:56,840 Speaker 1: primarily for use during the war. German systems operated at 249 00:14:56,880 --> 00:15:00,760 Speaker 1: three five mega hurts and five hundred sixty egga hurts, 250 00:15:00,760 --> 00:15:04,520 Speaker 1: which gave them superior resolution and accuracy, and it also 251 00:15:04,520 --> 00:15:07,200 Speaker 1: meant German systems had less noise to deal with. So 252 00:15:07,320 --> 00:15:11,479 Speaker 1: why is all this Well, remember that higher frequencies correspond 253 00:15:11,560 --> 00:15:15,760 Speaker 1: with shorter wavelengths. Shorter wavelengths are more narrow and thus 254 00:15:15,800 --> 00:15:18,360 Speaker 1: you can get a better picture of where something is 255 00:15:18,480 --> 00:15:22,720 Speaker 1: when you're using them. So remember that radar is essentially echolocation. 256 00:15:23,040 --> 00:15:25,840 Speaker 1: If you send out a very long wavelength and the 257 00:15:26,000 --> 00:15:28,920 Speaker 1: very long wavelength returns to you. You know the wavelength 258 00:15:29,000 --> 00:15:31,640 Speaker 1: encountered something that it reflected off of, but it's harder 259 00:15:31,680 --> 00:15:34,400 Speaker 1: to figure out exactly where that object is because the 260 00:15:34,480 --> 00:15:38,320 Speaker 1: wavelength is literally covering more space. You can tell how 261 00:15:38,400 --> 00:15:40,880 Speaker 1: far away the object is, and the way you do 262 00:15:40,920 --> 00:15:42,680 Speaker 1: that is you measure the amount of time it took 263 00:15:42,720 --> 00:15:46,040 Speaker 1: the radio wave to leave the transmitter and then return 264 00:15:46,120 --> 00:15:49,080 Speaker 1: to the receiver. You know that radio waves are traveling 265 00:15:49,080 --> 00:15:51,640 Speaker 1: at the speed of light, so you take the amount 266 00:15:51,680 --> 00:15:53,280 Speaker 1: of time it took for the radio wave to go 267 00:15:53,400 --> 00:15:56,560 Speaker 1: out and back. Then you take half of that number, 268 00:15:57,160 --> 00:15:59,400 Speaker 1: and you multiply at times the speed of light, and 269 00:15:59,440 --> 00:16:02,560 Speaker 1: you get the sense of the object. You have the 270 00:16:02,640 --> 00:16:05,880 Speaker 1: number because otherwise you have the round trip. Right, that's 271 00:16:05,920 --> 00:16:10,760 Speaker 1: just the full distance between you and the target object doubled, 272 00:16:10,840 --> 00:16:13,200 Speaker 1: so you have to take one half of that. Further, 273 00:16:13,680 --> 00:16:16,800 Speaker 1: by looking for any changes in wavelength, you can determine 274 00:16:16,840 --> 00:16:20,000 Speaker 1: if the object is moving towards you or away from you. 275 00:16:20,360 --> 00:16:23,960 Speaker 1: This again is that Doppler effect. If the returning wavelengths 276 00:16:24,000 --> 00:16:26,640 Speaker 1: are the same as the ones you sent out, the 277 00:16:26,680 --> 00:16:30,480 Speaker 1: object you detected is sitting still relative to your position. 278 00:16:30,920 --> 00:16:34,000 Speaker 1: If the wavelengths are shorter than the object is moving 279 00:16:34,040 --> 00:16:36,760 Speaker 1: toward you, And if the wavelengths are longer than what 280 00:16:36,840 --> 00:16:39,360 Speaker 1: you sent out, then the object is moving away from you. 281 00:16:39,920 --> 00:16:42,920 Speaker 1: But if the wavelengths are already pretty long, you don't 282 00:16:42,960 --> 00:16:45,560 Speaker 1: have a lot of accuracy when you're looking at the feedback. 283 00:16:45,640 --> 00:16:48,480 Speaker 1: A narrower beam will give you a better idea of 284 00:16:48,520 --> 00:16:51,520 Speaker 1: exactly where in the sky the object is. This is 285 00:16:51,560 --> 00:16:55,360 Speaker 1: clearly more helpful in both military and peacetime operations. So 286 00:16:55,480 --> 00:16:58,320 Speaker 1: Germany was way ahead of everyone else in terms of 287 00:16:58,400 --> 00:17:01,840 Speaker 1: radar when World World War two began. The country had 288 00:17:01,880 --> 00:17:05,439 Speaker 1: deployed radar on ships and on ground defense stations. They 289 00:17:05,440 --> 00:17:08,760 Speaker 1: were using shorter wavelengths than just about anybody else. The 290 00:17:08,840 --> 00:17:13,080 Speaker 1: country continued to develop the technology until about nineteen forty. 291 00:17:13,600 --> 00:17:17,040 Speaker 1: So why did they stop Well, German leaders were confident 292 00:17:17,080 --> 00:17:19,400 Speaker 1: that the war would soon be over and Germany would 293 00:17:19,400 --> 00:17:23,679 Speaker 1: be victorious, so they stopped work on radar to concentrate 294 00:17:23,720 --> 00:17:26,919 Speaker 1: on the war effort. Meanwhile, the UK and the US 295 00:17:27,000 --> 00:17:31,400 Speaker 1: were stepping up their efforts accelerating the evolution of the technology. 296 00:17:31,440 --> 00:17:33,520 Speaker 1: By the time Germany determined that the end of the 297 00:17:33,560 --> 00:17:36,320 Speaker 1: war was still years away, it was too late the 298 00:17:36,359 --> 00:17:40,000 Speaker 1: country was hopelessly left behind in terms of radar tech. 299 00:17:40,800 --> 00:17:42,600 Speaker 1: And now we touch on the part of the story 300 00:17:42,640 --> 00:17:45,359 Speaker 1: that I've mentioned in recent episodes about Alfred Loomis and 301 00:17:45,400 --> 00:17:50,040 Speaker 1: the Loran system. Scientists at the University of Birmingham developed 302 00:17:50,080 --> 00:17:55,000 Speaker 1: a cavity magnatron oscillator to produce waves in the microwave frequency, 303 00:17:55,040 --> 00:17:58,800 Speaker 1: and I'm talking about Birmingham in the UK hunt Alabama. 304 00:17:59,160 --> 00:18:03,320 Speaker 1: These devices used electric and magnetic fields to stimulate microwave 305 00:18:03,359 --> 00:18:07,880 Speaker 1: generation and chambers called cavities within a vacuum tube like device. 306 00:18:08,600 --> 00:18:11,760 Speaker 1: Microwaves can have a wavelength of between one meter all 307 00:18:11,760 --> 00:18:14,680 Speaker 1: the way down to one millimeter, and that gives them 308 00:18:14,680 --> 00:18:19,000 Speaker 1: frequencies of between three hundred megahurts to three hundred giga hurts. 309 00:18:19,359 --> 00:18:22,280 Speaker 1: The scientists at the University of Birmingham had created a 310 00:18:22,359 --> 00:18:26,240 Speaker 1: cavity magnetron capable of producing microwaves that were about ten 311 00:18:26,320 --> 00:18:29,840 Speaker 1: centimeters in wavelength, meaning they were very close to three 312 00:18:29,840 --> 00:18:33,160 Speaker 1: giga hurts and frequency. If used with radar, this would 313 00:18:33,160 --> 00:18:37,600 Speaker 1: make a system capable of unprecedented accuracy and resolution. But 314 00:18:37,680 --> 00:18:40,840 Speaker 1: the scientists needed help, and so they traveled to America 315 00:18:41,200 --> 00:18:44,040 Speaker 1: to meet with experts at M i T Now to 316 00:18:44,119 --> 00:18:48,600 Speaker 1: avoid suspicion, Taffy Bowen, a British scientist, traveled to the 317 00:18:48,720 --> 00:18:52,720 Speaker 1: United States under the pretense of going on holiday. He 318 00:18:52,800 --> 00:18:55,560 Speaker 1: made the trip aboard a cruise ship called the Duchess 319 00:18:55,680 --> 00:18:58,520 Speaker 1: of Richmond, which is not a bad way to deliver 320 00:18:58,600 --> 00:19:03,400 Speaker 1: top secret technology to allies across the ocean. The scientists 321 00:19:03,520 --> 00:19:07,680 Speaker 1: collaborated together and they created the newly formed rad Lab 322 00:19:07,840 --> 00:19:11,679 Speaker 1: at m I T to develop microwave radar technology. The 323 00:19:11,800 --> 00:19:15,359 Speaker 1: United States Navy was the actual entity to name the 324 00:19:15,400 --> 00:19:19,040 Speaker 1: technology radar, and originally that was an acronym that stood 325 00:19:19,040 --> 00:19:22,600 Speaker 1: for radio detection and ranging. These days, it's just a 326 00:19:22,600 --> 00:19:24,840 Speaker 1: regular noun. We just call it radar. You don't have 327 00:19:24,880 --> 00:19:27,960 Speaker 1: to capitalize it either. One other thing to note about 328 00:19:28,000 --> 00:19:33,280 Speaker 1: this time. On December seven, ninety one, and Army radar 329 00:19:33,359 --> 00:19:36,240 Speaker 1: site picked up a signal that indicated more than a 330 00:19:36,400 --> 00:19:40,960 Speaker 1: hundred aircraft were on approach to Hawaii. George Elliott, one 331 00:19:41,000 --> 00:19:44,240 Speaker 1: of the two operators of the radar site, passed this 332 00:19:44,320 --> 00:19:46,760 Speaker 1: information up the chain of command, but no one acted 333 00:19:46,840 --> 00:19:50,200 Speaker 1: upon it. According to Elliott, he and his co operator, 334 00:19:50,280 --> 00:19:53,000 Speaker 1: Joe Lockard were to run the station only between the 335 00:19:53,040 --> 00:19:56,200 Speaker 1: hours of four and seven a m. But Elliott wanted 336 00:19:56,200 --> 00:19:58,439 Speaker 1: to get in a bit more experience. He was brand 337 00:19:58,440 --> 00:20:01,119 Speaker 1: new to operating radars, so he wanted to practice for 338 00:20:01,160 --> 00:20:03,280 Speaker 1: a while, so he kept the system running for a 339 00:20:03,280 --> 00:20:05,960 Speaker 1: few minutes after seven am, and it was seven oh 340 00:20:06,000 --> 00:20:08,200 Speaker 1: two when he saw the large reading. It was actually 341 00:20:08,359 --> 00:20:11,280 Speaker 1: larger than any other reading they had previously seen at 342 00:20:11,320 --> 00:20:14,240 Speaker 1: that station. After calling in the report, he was told 343 00:20:14,560 --> 00:20:17,080 Speaker 1: that it was likely a group of US bombers heading 344 00:20:17,080 --> 00:20:21,640 Speaker 1: towards San Francisco. But then the Japanese forces unleashed a 345 00:20:21,680 --> 00:20:25,359 Speaker 1: devastating attack on Pearl Harbor, which would pull the United 346 00:20:25,359 --> 00:20:30,080 Speaker 1: States into World War Two. The microwave radar technology began 347 00:20:30,119 --> 00:20:33,240 Speaker 1: to get a rapid deployment in the early nineteen forties 348 00:20:33,280 --> 00:20:35,480 Speaker 1: as part of a top secret effort to gain an 349 00:20:35,520 --> 00:20:39,200 Speaker 1: advantage in the war. The Axis forces had learned how 350 00:20:39,200 --> 00:20:43,480 Speaker 1: to jam earlier radar systems like the SCR TO six eight, 351 00:20:43,800 --> 00:20:47,040 Speaker 1: which used longer radio waves, and that was from the 352 00:20:47,119 --> 00:20:50,600 Speaker 1: United States and it operated on a much lower frequency 353 00:20:50,600 --> 00:20:53,399 Speaker 1: than the microwave radar stations they were, so the Germans 354 00:20:53,400 --> 00:20:56,320 Speaker 1: were unprepared for the high precision of the new microwave 355 00:20:56,359 --> 00:20:59,640 Speaker 1: systems that were represented in the s c R five 356 00:20:59,720 --> 00:21:03,600 Speaker 1: eight four radar designation. The new radar had a parabolic 357 00:21:03,720 --> 00:21:07,320 Speaker 1: reflector antenna that measured two meters or about six point 358 00:21:07,359 --> 00:21:10,080 Speaker 1: six feet in diameter, and it was first used in 359 00:21:10,160 --> 00:21:13,480 Speaker 1: combat in nineteen forty four in Italy to great effect. 360 00:21:13,760 --> 00:21:17,080 Speaker 1: Many different versions of radar were developed and deployed during 361 00:21:17,119 --> 00:21:20,720 Speaker 1: the war, including radar systems aboard aircraft and those on 362 00:21:20,880 --> 00:21:25,800 Speaker 1: naval vessels. On May nine, a German warship called the 363 00:21:25,880 --> 00:21:29,320 Speaker 1: Bismarck sunk a British ship called the h MS Hood, 364 00:21:29,640 --> 00:21:33,080 Speaker 1: but a British aircraft carrier called the Arc Royal used 365 00:21:33,160 --> 00:21:36,679 Speaker 1: shipborn radar to detect and track the Bismarck, and that 366 00:21:36,760 --> 00:21:40,840 Speaker 1: allowed Allied forces to converge and attack the ship, ultimately 367 00:21:40,960 --> 00:21:45,240 Speaker 1: sinking it. After World War Two ended, Winston Churchill would 368 00:21:45,280 --> 00:21:48,000 Speaker 1: say that while the atomic bomb may have ended the war, 369 00:21:48,680 --> 00:21:52,240 Speaker 1: radar was the technology that won the war. Now I 370 00:21:52,240 --> 00:21:54,760 Speaker 1: have a little bit more to say about radar, but 371 00:21:54,840 --> 00:21:57,640 Speaker 1: first let's take another quick break to thank our sponsor. 372 00:22:05,119 --> 00:22:07,800 Speaker 1: Towards the end of World War Two, the UK and 373 00:22:07,840 --> 00:22:10,760 Speaker 1: the US had both worked with radar to aid with 374 00:22:10,960 --> 00:22:15,520 Speaker 1: landing aircraft to guide them into landing strips safely. And 375 00:22:15,600 --> 00:22:19,399 Speaker 1: that use of radar quickly expanded to civil oberations, and 376 00:22:19,440 --> 00:22:22,000 Speaker 1: that would become the basis of air traffic control. And 377 00:22:22,040 --> 00:22:24,959 Speaker 1: at first they would use this just for the purposes 378 00:22:25,080 --> 00:22:27,919 Speaker 1: of guiding aircraft to land at landing strips or to 379 00:22:27,960 --> 00:22:32,120 Speaker 1: take off, and then ultimately to become more of a 380 00:22:32,160 --> 00:22:35,480 Speaker 1: holistic air traffic control system that could be handed off 381 00:22:35,520 --> 00:22:40,159 Speaker 1: from one control tower to another to maintain contact with 382 00:22:40,280 --> 00:22:45,280 Speaker 1: pilots as they traveled across vast distances. Advances in radar 383 00:22:45,320 --> 00:22:49,800 Speaker 1: also helped fuel more study in radio astronomy. Radio astronomy 384 00:22:49,920 --> 00:22:53,639 Speaker 1: uses large arrays of radio antenna to detect extra terrestrial 385 00:22:53,880 --> 00:22:57,240 Speaker 1: radio signals, And by that I don't necessarily mean we're 386 00:22:57,240 --> 00:23:00,600 Speaker 1: listening to the equivalent of alien television rerun ones. In fact, 387 00:23:00,640 --> 00:23:03,440 Speaker 1: I don't mean that at all, because lots of stuff 388 00:23:03,520 --> 00:23:07,240 Speaker 1: emits radio waves. So we're talking about studying signals from 389 00:23:07,320 --> 00:23:13,240 Speaker 1: various celestial phenomenas just stars, galaxies, quasars, pulsars, and more. 390 00:23:13,680 --> 00:23:16,040 Speaker 1: Another use of radar that grew out of military use 391 00:23:16,160 --> 00:23:20,880 Speaker 1: was for meteorology. During the war, radar operators noted that 392 00:23:20,920 --> 00:23:25,160 Speaker 1: many times they detected excess noise or clutter when they 393 00:23:25,280 --> 00:23:30,400 Speaker 1: directed radar transmissions towards weather elements like precipitation. After the war, 394 00:23:30,720 --> 00:23:35,080 Speaker 1: engineers and scientists began to adapt radar to track storms, Specifically, 395 00:23:35,440 --> 00:23:40,160 Speaker 1: special radar systems that could detect precipitation, including how intense 396 00:23:40,240 --> 00:23:44,240 Speaker 1: that precipitation was, began to help meteorologists track weather patterns 397 00:23:44,440 --> 00:23:47,440 Speaker 1: and adjust forecasts. So you may have heard of Doppler 398 00:23:47,560 --> 00:23:50,840 Speaker 1: radar on your local weather forecast. That's what's talking about. 399 00:23:50,840 --> 00:23:54,719 Speaker 1: Their using radar to detect things like precipitation and the 400 00:23:54,760 --> 00:23:59,640 Speaker 1: movement of these thunderstorms and weather patterns. Other advances include 401 00:23:59,720 --> 00:24:03,239 Speaker 1: pull Doppler radar, and it's pretty much what sounds like. 402 00:24:03,320 --> 00:24:08,000 Speaker 1: It sends out signals and pulses and then that is 403 00:24:08,400 --> 00:24:11,159 Speaker 1: very useful. It helps limit the amount of noise that 404 00:24:11,240 --> 00:24:15,560 Speaker 1: comes back when you are detecting the returning radio waves. 405 00:24:15,920 --> 00:24:17,479 Speaker 1: So the way this would work, if you wanted to, 406 00:24:17,600 --> 00:24:21,000 Speaker 1: I don't know, create a radar speed gun like the 407 00:24:21,280 --> 00:24:24,440 Speaker 1: police use. This was part of the request. You would 408 00:24:24,520 --> 00:24:28,960 Speaker 1: have a velocity threshold and this would essentially tell the 409 00:24:29,000 --> 00:24:33,760 Speaker 1: system ignore anything below a certain threshold as far as 410 00:24:33,880 --> 00:24:37,600 Speaker 1: velocity goes. So if it detects that an object is 411 00:24:37,640 --> 00:24:42,000 Speaker 1: traveling slower than the velocity threshold, it ignores it, which 412 00:24:42,000 --> 00:24:45,280 Speaker 1: is really useful if you're doing something like using a 413 00:24:45,359 --> 00:24:48,240 Speaker 1: radar gun to detect speed. If you're pointing it down 414 00:24:48,320 --> 00:24:51,200 Speaker 1: the street and a car passes by and it's well 415 00:24:51,280 --> 00:24:55,560 Speaker 1: below the threshold, then it shouldn't even activate the warning. 416 00:24:55,680 --> 00:24:59,040 Speaker 1: Or if your radar is picking up something apart from 417 00:24:59,080 --> 00:25:02,160 Speaker 1: just a car, if it's below that threshold, it doesn't 418 00:25:02,160 --> 00:25:04,719 Speaker 1: come back as a false hit. Otherwise you could end 419 00:25:04,760 --> 00:25:08,760 Speaker 1: up getting signals bounced off of all sorts of different surfaces, 420 00:25:08,800 --> 00:25:11,160 Speaker 1: and the radar gun would be confused as to which 421 00:25:11,200 --> 00:25:14,960 Speaker 1: one's meant what. You would pick up these signals, some 422 00:25:15,080 --> 00:25:17,439 Speaker 1: of which would indicate that there were objects moving, some 423 00:25:17,520 --> 00:25:20,200 Speaker 1: of which said that there's not objects moving. And this 424 00:25:20,240 --> 00:25:22,320 Speaker 1: is where we get to that noise and clutter and 425 00:25:22,640 --> 00:25:28,359 Speaker 1: UH problems. So clutter is the the return signals you 426 00:25:28,400 --> 00:25:32,400 Speaker 1: get from a radar transmitter that aren't related to whatever 427 00:25:32,440 --> 00:25:34,800 Speaker 1: your target is. So it's very easy to understand with 428 00:25:34,840 --> 00:25:37,679 Speaker 1: a radar gun, your target is a car. You're pointing 429 00:25:37,680 --> 00:25:40,320 Speaker 1: a radar gun at a car. You're getting some signals 430 00:25:40,320 --> 00:25:42,320 Speaker 1: bouncing back. Some of them are bouncing back from the car. 431 00:25:42,440 --> 00:25:44,399 Speaker 1: Some of them are bouncing back from other vehicles on 432 00:25:44,440 --> 00:25:46,680 Speaker 1: the road. Some of them may be bouncing back from 433 00:25:46,720 --> 00:25:49,119 Speaker 1: just the surface of the ground, and you want to 434 00:25:49,160 --> 00:25:52,199 Speaker 1: be able to make sure you're looking specifically at the 435 00:25:52,240 --> 00:25:56,639 Speaker 1: signals that are related to the target. Everything else is clutter, 436 00:25:56,840 --> 00:26:00,800 Speaker 1: it's distracting, and it could give you a false uh 437 00:26:00,840 --> 00:26:03,879 Speaker 1: information seat of information about whatever your target is. So 438 00:26:03,920 --> 00:26:05,680 Speaker 1: that's why you have to have something like a velocity 439 00:26:05,720 --> 00:26:09,639 Speaker 1: threshold to help eliminate a lot of that uh. There's 440 00:26:09,720 --> 00:26:14,000 Speaker 1: also the possibility that you would get noise from other 441 00:26:14,119 --> 00:26:17,480 Speaker 1: sources of radio waves. This is interference, so this is 442 00:26:17,520 --> 00:26:20,560 Speaker 1: not coming from your radar antenna. This is coming from 443 00:26:20,640 --> 00:26:24,760 Speaker 1: other sources and could also give false positives or clutter 444 00:26:24,840 --> 00:26:27,399 Speaker 1: up your information. So you want to have a device 445 00:26:27,480 --> 00:26:32,399 Speaker 1: that can very easily find the signal through all the noise. 446 00:26:32,920 --> 00:26:36,040 Speaker 1: On top of that, there is the concept of radar jamming, 447 00:26:36,119 --> 00:26:39,040 Speaker 1: and this is a very real thing. If you know 448 00:26:39,920 --> 00:26:43,840 Speaker 1: what frequency a radar system is using, and then you 449 00:26:43,880 --> 00:26:47,280 Speaker 1: broadcast that same frequency toward the radar. Let's say you've 450 00:26:47,320 --> 00:26:50,600 Speaker 1: got line of sight on the radar antenna. You could 451 00:26:50,600 --> 00:26:53,640 Speaker 1: broadcast that same frequency of radio waves at the antenna 452 00:26:53,680 --> 00:26:57,240 Speaker 1: and you're essentially overwhelming it it can't detect the returning 453 00:26:57,240 --> 00:27:04,520 Speaker 1: signals because it's getting blasted by the exact frequency continuously. 454 00:27:04,880 --> 00:27:07,480 Speaker 1: So it's just it's like it's continuously getting a hit, 455 00:27:07,720 --> 00:27:10,200 Speaker 1: and so it never knows when there's a real hit. 456 00:27:10,640 --> 00:27:13,320 Speaker 1: So radar jamming is an actual thing. And not only that, 457 00:27:13,960 --> 00:27:16,560 Speaker 1: but to make matters worse, you don't even need a 458 00:27:16,600 --> 00:27:20,840 Speaker 1: particularly powerful transmitter to jam radar. And the reason for 459 00:27:20,920 --> 00:27:24,840 Speaker 1: that is that radar radio signals they decrease in strength 460 00:27:24,920 --> 00:27:29,080 Speaker 1: as they travel. So if you're sending out a radar 461 00:27:29,160 --> 00:27:33,040 Speaker 1: signal from the transmitter, it's probably a very powerful signal, 462 00:27:33,240 --> 00:27:35,640 Speaker 1: but once it gets to wherever it's going, let's say 463 00:27:35,640 --> 00:27:39,560 Speaker 1: it's trying to detect aircraft, and then once those signals 464 00:27:39,560 --> 00:27:42,919 Speaker 1: return back to the receiver, they're pretty weak. So the 465 00:27:42,960 --> 00:27:45,760 Speaker 1: receiver has to be very sensitive to pick up those signals, 466 00:27:46,119 --> 00:27:48,879 Speaker 1: which means that if you have a transmitter of even 467 00:27:48,960 --> 00:27:52,280 Speaker 1: modest power, you could probably fool the receiver into thinking 468 00:27:52,320 --> 00:27:55,920 Speaker 1: it's picking up those signals all the time. So jammers 469 00:27:55,960 --> 00:27:58,600 Speaker 1: do not have to be as strong as radar transmitters 470 00:27:58,680 --> 00:28:01,760 Speaker 1: in order to still be a fact active, but you 471 00:28:01,800 --> 00:28:03,760 Speaker 1: do kind of have to have line of sight. You 472 00:28:03,760 --> 00:28:05,600 Speaker 1: can get a little bit off to one side or 473 00:28:05,640 --> 00:28:07,840 Speaker 1: the other, and then you can have what is called 474 00:28:07,880 --> 00:28:11,800 Speaker 1: a side lobe radar jammer, but that's not nearly as 475 00:28:11,800 --> 00:28:14,040 Speaker 1: effective as having a direct line of sight on on 476 00:28:14,119 --> 00:28:17,720 Speaker 1: the radar. Radars also these days tend to work as 477 00:28:17,760 --> 00:28:20,440 Speaker 1: both an antenna and a receiver. I mentioned that earlier 478 00:28:20,520 --> 00:28:24,080 Speaker 1: this idea of monostatic radar. In order to do that, 479 00:28:24,320 --> 00:28:26,800 Speaker 1: you have to have something called a duplex or a 480 00:28:26,880 --> 00:28:29,800 Speaker 1: duplex er is sort of the switch. It switches the 481 00:28:29,920 --> 00:28:33,479 Speaker 1: radar between transmit mode and receive mode. And typically the 482 00:28:33,520 --> 00:28:37,760 Speaker 1: way these work is that a radar will transmit for 483 00:28:37,920 --> 00:28:41,160 Speaker 1: just a few thousandths of a second, so a fraction 484 00:28:41,280 --> 00:28:44,240 Speaker 1: of a fraction of a second, it sends out blast 485 00:28:44,320 --> 00:28:46,920 Speaker 1: of radio signals, and then it listens for a while, 486 00:28:47,560 --> 00:28:49,200 Speaker 1: and then it will do the same thing again and 487 00:28:49,200 --> 00:28:52,360 Speaker 1: again and again, so every second it does it's only 488 00:28:52,360 --> 00:28:54,440 Speaker 1: transmitting for thousands of a second and the rest of 489 00:28:54,440 --> 00:28:57,000 Speaker 1: the time it's listening. This is the case for lots 490 00:28:57,000 --> 00:29:01,640 Speaker 1: of different radar systems up there, that including things like 491 00:29:01,720 --> 00:29:05,960 Speaker 1: CT where you're you're you're sending out signals briefly, but 492 00:29:06,040 --> 00:29:09,480 Speaker 1: you're really spending most of your time listening and so 493 00:29:09,640 --> 00:29:12,640 Speaker 1: the same is true with all radar systems really that 494 00:29:12,640 --> 00:29:16,080 Speaker 1: that rely on this monostatic approach. That is, then there's 495 00:29:16,120 --> 00:29:19,800 Speaker 1: some other related technologies that are not specifically radar, but 496 00:29:19,840 --> 00:29:23,000 Speaker 1: they work on a similar principle. So one of those 497 00:29:23,040 --> 00:29:27,240 Speaker 1: would be lidar. Lidar, as you might guess from the name, 498 00:29:27,520 --> 00:29:31,720 Speaker 1: it relies on light, infrared light and UH to be specific, 499 00:29:32,080 --> 00:29:36,400 Speaker 1: and infrared light. Light guns have largely replaced radar guns 500 00:29:36,440 --> 00:29:41,680 Speaker 1: for the police. And UH light is you know again, 501 00:29:41,720 --> 00:29:44,520 Speaker 1: it's it's signals are even shorter than things in the 502 00:29:44,560 --> 00:29:48,640 Speaker 1: microwave realm, so you can get even higher accuracy with 503 00:29:48,640 --> 00:29:51,680 Speaker 1: a more narrow beam, and it can cut down on 504 00:29:51,760 --> 00:29:55,200 Speaker 1: noise even more assuming you don't have an infrared generator 505 00:29:55,280 --> 00:29:58,920 Speaker 1: just blasting back at the light gun. So light guns 506 00:29:58,960 --> 00:30:02,760 Speaker 1: have largely replaced radar guns, although we have plenty of 507 00:30:02,840 --> 00:30:06,680 Speaker 1: uses for radar itself, not just not just in radar 508 00:30:06,760 --> 00:30:10,640 Speaker 1: guns these days. And then there's sonar that's the sound, 509 00:30:10,800 --> 00:30:16,920 Speaker 1: navigation and arranging. We use sonar for underwater applications. Things 510 00:30:16,960 --> 00:30:23,400 Speaker 1: like submarines use sonar to detect obstacles and navigate because, 511 00:30:23,520 --> 00:30:27,200 Speaker 1: as it turns out, electromagnetic waves don't travel all that 512 00:30:27,280 --> 00:30:31,360 Speaker 1: well through dense seawater, so we rely on these sonic 513 00:30:31,440 --> 00:30:35,920 Speaker 1: based systems for detecting objects underwater rather than using electromagnetic 514 00:30:35,920 --> 00:30:39,200 Speaker 1: waves because they're just not very effective once you get 515 00:30:39,640 --> 00:30:43,040 Speaker 1: below a certain depth. So most submarines have both radar 516 00:30:43,120 --> 00:30:45,520 Speaker 1: and so in our systems, but the radar systems are 517 00:30:45,600 --> 00:30:50,000 Speaker 1: used when the submarine has surfaced, and typically you would 518 00:30:50,040 --> 00:30:52,840 Speaker 1: use it if you were navigating into port, for example, 519 00:30:53,160 --> 00:30:55,800 Speaker 1: and whenever you're underwater you would use the sonar system. 520 00:30:56,760 --> 00:30:59,240 Speaker 1: So that kind of wraps up this discussion of radar. 521 00:30:59,280 --> 00:31:01,000 Speaker 1: There a lot of other particular as We could talk 522 00:31:01,040 --> 00:31:05,120 Speaker 1: about specific variations on radar, things like phase shifting, that 523 00:31:05,160 --> 00:31:09,240 Speaker 1: sort of stuff, but it gets really technical, and honestly, 524 00:31:09,440 --> 00:31:12,400 Speaker 1: it's just variations on what I've already talked about using 525 00:31:12,840 --> 00:31:16,480 Speaker 1: different elements of the physics of radio waves. And while 526 00:31:16,480 --> 00:31:20,680 Speaker 1: it's fascinating, it's also again hard to describe without the 527 00:31:20,720 --> 00:31:23,440 Speaker 1: use of visual aids. But I hope that this was 528 00:31:23,480 --> 00:31:26,479 Speaker 1: an interesting episode for you guys. I love looking into 529 00:31:26,480 --> 00:31:29,640 Speaker 1: technologies like this. If there's a technology you would like 530 00:31:29,680 --> 00:31:31,520 Speaker 1: me to cover in a future episode of Tech Stuff, 531 00:31:31,720 --> 00:31:33,400 Speaker 1: or maybe there's someone you would like me to talk 532 00:31:33,440 --> 00:31:36,280 Speaker 1: about or two. You should send me a message and 533 00:31:36,360 --> 00:31:38,640 Speaker 1: let me know. 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