WEBVTT 00:00:00.160 --> 00:00:07.440 Maybe it's just because I'm old, but even though Spotify, podcasts, and other 00:00:05.120 --> 00:00:11.679 forms of audio streaming seem to rule the day, there's just something 00:00:09.440 --> 00:00:15.440 comforting about the simplicity of turning a knob on the radio and 00:00:13.440 --> 00:00:20.240 listening to what's happening on the airwaves. Even in the digital age, radio 00:00:18.400 --> 00:00:25.760 has maintained a fair amount of popularity since the first public 00:00:22.560 --> 00:00:28.800 broadcasts in the early 20th century. 00:00:25.760 --> 00:00:31.199 But since radio has been around since 00:00:28.800 --> 00:00:36.800 long before we had things like digital decoders that turn electrical impulses 00:00:33.360 --> 00:00:39.360 into music, how the heck do simple cheap 00:00:36.800 --> 00:00:44.079 radios know how to convert an electromagnetic radio signal into a I 00:00:42.320 --> 00:00:49.840 don't know, let's say a basketball game or a weather report or a you know Justin 00:00:47.840 --> 00:00:55.840 Bieber's greatest who put that crap in my script. Anyway, AM radio broadcasts 00:00:53.520 --> 00:01:02.320 showed up before FM. So, we'll start with those. An AM station will broadcast 00:00:58.879 --> 00:01:04.960 a signal at a constant frequency, but 00:01:02.320 --> 00:01:10.720 will add the soundwave representing the actual audio to that base signal. It's 00:01:08.240 --> 00:01:15.840 also called a carrier wave, resulting in the height or amplitude of the wave 00:01:13.280 --> 00:01:21.600 changing accordingly. This is where the term AM comes from, as it stands for 00:01:18.799 --> 00:01:28.240 amplitude modulation. You can get your radio to play back this signal as actual 00:01:24.560 --> 00:01:29.920 music or dialogue by tuning it to 00:01:28.240 --> 00:01:34.960 whatever frequency the station that you're looking for broadcasts at. This 00:01:32.720 --> 00:01:39.840 makes your antenna resonate at the frequency and ignore everything else in 00:01:37.520 --> 00:01:45.200 the air. So, very simple radio tuners are actually little more than coils of 00:01:42.720 --> 00:01:50.240 wire. How many turns of the wire will determine what frequency you're picking 00:01:47.280 --> 00:01:54.399 up. Cool, right? The antenna actually creates an electrical current that 00:01:52.079 --> 00:01:58.479 corresponds to the radio signal. This current is sent to other parts of your 00:01:56.479 --> 00:02:03.040 radio that filter out the irrelevant parts of the signal and send it to your 00:02:00.719 --> 00:02:08.239 speakers or your headphones as changes in voltage which drive those speakers 00:02:05.680 --> 00:02:12.800 and produce sound. It's actually pretty remarkable that this is all done without 00:02:10.399 --> 00:02:19.760 any digital decoding by something like a a CPU. It's a completely analog process 00:02:17.040 --> 00:02:26.000 that made it possible for news, music, and entertainment to stream into homes 00:02:22.239 --> 00:02:28.160 decades before the internet or even TV. 00:02:26.000 --> 00:02:32.239 FM broadcasting works somewhat similarly, though with FM, it's the 00:02:30.480 --> 00:02:38.720 frequency of the signal that gets changed, hence the F in FM. FM radios 00:02:36.640 --> 00:02:44.319 have a special transformer inside them that basically sits idle as long as 00:02:41.680 --> 00:02:48.800 exactly whatever frequency you're tuned to hits your antenna. But once it 00:02:46.879 --> 00:02:53.040 detects a small change in that frequency, it outputs a voltage that 00:02:51.120 --> 00:02:59.920 makes your speakers emit a certain sound. So let's say you're tuned to 99.5 00:02:56.480 --> 00:03:02.319 FM on your dial. Since FM works by using 00:02:59.920 --> 00:03:10.400 very small changes in frequency to carry a signal, you are actually tuned to 00:03:05.280 --> 00:03:12.560 signals just above and below 99.5 MHz, 00:03:10.400 --> 00:03:18.000 which makes that transformer send the voltage to your speakers. Now, although 00:03:15.360 --> 00:03:24.159 this process makes FM more complicated to engineer than AM, you often get a 00:03:20.959 --> 00:03:26.400 much clearer, higher quality signal. FM 00:03:24.159 --> 00:03:31.360 is less susceptible to interference as well because interference often 00:03:28.239 --> 00:03:34.400 manifests as amplitude spikes. An AM 00:03:31.360 --> 00:03:36.400 radio would see these spikes as actual 00:03:34.400 --> 00:03:40.959 sound to produce and it would end up coming out of your speakers while FM 00:03:38.720 --> 00:03:45.760 cares about variations in frequency rather than amplitude. So an FM radio 00:03:43.440 --> 00:03:49.440 can just ignore that type of interference and the death metal you're 00:03:47.760 --> 00:03:55.920 listening to will come out sounding just as clear and angry as ever. FM also has 00:03:54.159 --> 00:03:59.840 the advantage of having much higher bandwidth than AM due to the 00:03:57.599 --> 00:04:05.599 mathematical properties of frequency modulation. This allows for lots of 00:04:02.959 --> 00:04:11.599 wiggle room in the signal to create more sounds more accurately, making FM the 00:04:08.720 --> 00:04:15.599 clear choice for music, while AM is often just fine for stuff where 00:04:13.280 --> 00:04:22.240 highfidelity isn't a big deal, such as talk radio. But if FM is so superior, 00:04:18.880 --> 00:04:25.840 then why do AM stations seem to have so 00:04:22.240 --> 00:04:28.160 much better range? Well, it's because AM 00:04:25.840 --> 00:04:33.040 wavelengths are much longer, meaning that they can move more effectively 00:04:30.960 --> 00:04:37.840 following even the curvature of the Earth and deal with obstacles like 00:04:35.520 --> 00:04:43.440 buildings, whereas you can quickly lose highfrequency FM signals if you start 00:04:40.560 --> 00:04:48.400 putting stuff in the way. AM frequencies also allow signals to cause free 00:04:45.680 --> 00:04:53.440 electrons in the ionosphere to oscillate at the same frequency as the radio wave 00:04:50.800 --> 00:04:58.479 that hits them. Meaning that AM signals can actually reflect off the upper 00:04:55.919 --> 00:05:02.479 atmosphere. At night, there are more free electrons hanging out in the sky, 00:05:00.320 --> 00:05:06.960 which is why you can sometimes hear AM stations from hundreds of miles away 00:05:04.880 --> 00:05:12.320 after the sun goes down, as opposed to FM, which tends to go right through the 00:05:09.520 --> 00:05:15.840 atmosphere. Of course, this may not seem impressive when the internet allows you 00:05:14.000 --> 00:05:20.000 to listen to highquality digital broadcasts from the other side of the 00:05:17.520 --> 00:05:25.440 world, no problem. But good old analog radio still has the distinct advantage 00:05:22.080 --> 00:05:28.400 of only requiring a $10 receiver with no 00:05:25.440 --> 00:05:33.039 subscription fees and very high ease of use, especially for people who might not 00:05:30.639 --> 00:05:36.960 be terribly tech-savvy. And of course, your radio will keep working even if 00:05:35.199 --> 00:05:43.440 your finicky internet connection goes out. 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