WEBVTT

0:00:02.940000 --> 0:00:07.400000
 Hello and welcome to this video titled
 Radio Frequency Explained.

0:00:07.400000 --> 0:00:10.020000
 I have three main things I
 want to go through here.

0:00:10.020000 --> 0:00:12.040000
 What is frequency?

0:00:12.040000 --> 0:00:15.280000
 You may have used that
 term in other contexts.

0:00:15.280000 --> 0:00:18.780000
 The frequency that my ex-wife
 contacts me is far too often.

0:00:18.780000 --> 0:00:21.880000
 Well, you get an idea here of what frequency
 might relate to, but we're

0:00:21.880000 --> 0:00:24.800000
 going to talk about it in the
 context of radio frequencies.

0:00:24.800000 --> 0:00:28.020000
 I'm going to define the term frequency
 from a physics standpoint.

0:00:28.020000 --> 0:00:32.360000
 And then we're going to look at what
 is radio frequency, and then we're

0:00:32.360000 --> 0:00:35.320000
 going to finalize it with something
 called ISM bands.

0:00:35.320000 --> 0:00:37.660000
 So let's start out with
 this term of frequency.

0:00:37.660000 --> 0:00:42.800000
 What do we mean by frequency
 in the terms of Wi-Fi?

0:00:42.800000 --> 0:00:47.880000
 So frequency technically is a measurement
 of how often something changes

0:00:47.880000 --> 0:00:50.640000
 over a given time interval.

0:00:50.640000 --> 0:00:54.440000
 And a long time ago, a very smart
 man said, you know what?

0:00:54.440000 --> 0:00:59.640000
 Let's create a name of this, and
 we're going to call it the Hertz.

0:00:59.640000 --> 0:01:02.420000
 So no, this is not the car
 rental company Hertz.

0:01:02.420000 --> 0:01:06.340000
 This is a scientific measurement
 of frequency.

0:01:06.340000 --> 0:01:11.300000
 It's a measurement of how frequently
 something changes over one second.

0:01:11.300000 --> 0:01:17.100000
 So if I say that something has a frequency
 of one Hertz, that means that

0:01:17.100000 --> 0:01:21.580000
 however it's changing is it's
 changing once every second.

0:01:21.580000 --> 0:01:26.540000
 So remember that one Hertz equals
 one change in one second.

0:01:26.540000 --> 0:01:29.040000
 Now as we're going to see here in just
 a moment, when we're talking about

0:01:29.040000 --> 0:01:34.060000
 Wi-Fi, we're talking about millions
 or even billions of changes in one

0:01:34.060000 --> 0:01:37.520000
 second of time. So we're not going
 to be talking about one Hertz.

0:01:37.520000 --> 0:01:42.340000
 We're going to be talking about mega
 Hertz's, mega in millions or giga

0:01:42.340000 --> 0:01:46.680000
 Hertz's, which are billions
 of changes per second.

0:01:46.680000 --> 0:01:51.380000
 So now let's trans...

0:01:51.380000 --> 0:01:51.780000
 So what we're going to be talking about
 is how this is going to be applied,

0:01:51.780000 --> 0:01:54.260000
 how is this relate to
 radio frequencies?

0:01:54.260000 --> 0:01:58.520000
 Well, to understand radio frequencies,
 we have to start with a higher

0:01:58.520000 --> 0:02:02.740000
 level topic, which is electromagnetic
 radiation.

0:02:02.740000 --> 0:02:07.900000
 Radiation that has both electrical
 and magnetic properties.

0:02:07.900000 --> 0:02:14.660000
 Now, electric magnetic radiation at
 its essence is any time an electron

0:02:14.660000 --> 0:02:18.580000
 moves, especially if it moves in,
 for example, a copper cable.

0:02:18.580000 --> 0:02:22.080000
 If you have a copper cable and somehow
 you can get the electrons to move

0:02:22.080000 --> 0:02:26.200000
 in that copper cable, for example, you
 send a current down a copper cable.

0:02:26.200000 --> 0:02:30.800000
 If I have a piece of wire and I attach
 two batteries on either end of

0:02:30.800000 --> 0:02:35.060000
 that copper cable and now I've got
 electrons moving through it, well,

0:02:35.060000 --> 0:02:39.080000
 I'm actually producing electromagnetic
 radiation.

0:02:39.080000 --> 0:02:41.900000
 You probably... You're not going to
 be able to sense it with your human

0:02:41.900000 --> 0:02:45.480000
 faculties, but if you put some testing
 instruments right up next to that

0:02:45.480000 --> 0:02:49.340000
 cable, you'll be able to detect the electromagnetic
 radiation that's being

0:02:49.340000 --> 0:02:51.240000
 emitted from it.

0:02:51.240000 --> 0:02:55.360000
 And typically speaking, electromagnetic
 radiation, once it's emitted,

0:02:55.360000 --> 0:02:58.360000
 is in like 90 degrees
 from the electricity.

0:02:58.360000 --> 0:02:59.200000
 What do I mean by that?

0:02:59.200000 --> 0:03:06.000000
 Well, imagine that my cable, for example,
 here's my cable and I don't

0:03:06.000000 --> 0:03:09.900000
 remember what the symbol is for a battery,
 but let's say here's a battery

0:03:09.900000 --> 0:03:14.800000
 right here and here's
 a battery right here.

0:03:14.800000 --> 0:03:19.360000
 And so the direction of the electrons
 on this cable are going this way,

0:03:19.360000 --> 0:03:21.900000
 right? They're going back
 and forth this way.

0:03:21.900000 --> 0:03:26.440000
 Well 90 degrees from that
 would be this way.

0:03:26.440000 --> 0:03:30.640000
 So this is actually the direction
 of the electromagnetic radiation.

0:03:30.640000 --> 0:03:36.940000
 And if you imagine this in three dimensions,
 if this was the cable, if

0:03:36.940000 --> 0:03:39.800000
 we were facing it head on, if I had
 the cable pointing directly at you

0:03:39.800000 --> 0:03:43.780000
 and we're facing the cable head on right
 here, the electromagnetic radiation

0:03:43.780000 --> 0:03:49.720000
 goes out in all directions
 from it.

0:03:49.720000 --> 0:03:52.440000
 So right now the electrons are
 poking you in the eye, right?

0:03:52.440000 --> 0:03:56.300000
 They're coming through this cable and
 the electromagnetic radiation is

0:03:56.300000 --> 0:03:59.160000
 going out in 90 degrees from that.


0:03:59.160000 --> 0:04:04.300000
 So electromagnetic radiation is very
 simple to create at its basis.

0:04:04.300000 --> 0:04:06.560000
 That's really what it is.

0:04:06.560000 --> 0:04:09.780000
 Now also notice here that electromagnetic
 radiation has two properties.

0:04:09.780000 --> 0:04:14.160000
 It has an electrical component
 and a magnetic component.

0:04:14.160000 --> 0:04:18.700000
 And if you've got the correct
 sensors, you can sense this.

0:04:18.700000 --> 0:04:21.520000
 You can sense the electrical component
 and you can sense the magnetic

0:04:21.520000 --> 0:04:24.440000
 component of EMR.

0:04:24.440000 --> 0:04:28.400000
 And here's the really cool sort
 of freaky thing about EMR.

0:04:28.400000 --> 0:04:31.560000
 It requires no medium
 to propagate.

0:04:31.560000 --> 0:04:35.200000
 It can even go through
 the vacuum of space.

0:04:35.200000 --> 0:04:41.160000
 You may have read a long time ago
 or heard about SETI, right?

0:04:41.160000 --> 0:04:43.860000
 The search for extraterrestrial
 intelligence.

0:04:43.860000 --> 0:04:45.180000
 I don't know how big SETI is.

0:04:45.180000 --> 0:04:46.840000
 These days, I don't even
 know if they still exist.

0:04:46.840000 --> 0:04:50.340000
 But one of the things they were really
 big on a couple of decades ago

0:04:50.340000 --> 0:04:55.180000
 was throughout the world, they would
 put up these big radio telescopes.

0:04:55.180000 --> 0:04:56.680000
 And what was the idea of this?

0:04:56.680000 --> 0:05:00.280000
 They would point at the stars and they
 were trying to detect electromagnetic

0:05:00.280000 --> 0:05:06.000000
 radiation that was coming from space
 that wasn't just normally coming

0:05:06.000000 --> 0:05:09.900000
 from a gamma explosion of a neutron star
 or something, but electromagnetic

0:05:09.900000 --> 0:05:15.600000
 radiation that was changing, that seemed
 to be artificially induced or

0:05:15.600000 --> 0:05:16.620000
 changed in some way.

0:05:16.620000 --> 0:05:19.920000
 And ah, that must be an alien from the
 gamma quadrant or something like

0:05:19.920000 --> 0:05:23.300000
 that. So that's the cool thing about
 electromagnetic radiation.

0:05:23.300000 --> 0:05:25.300000
 It goes through space.

0:05:25.300000 --> 0:05:26.780000
 It doesn't require air.

0:05:26.780000 --> 0:05:28.500000
 It doesn't require a cable.

0:05:28.500000 --> 0:05:30.600000
 It's going through your
 body right now.

0:05:30.600000 --> 0:05:33.600000
 If I was standing right next to you
 and I turn on a radio and I turn it

0:05:33.600000 --> 0:05:38.040000
 to 98.7 country music, the signal I'm
 getting could very well be coming

0:05:38.040000 --> 0:05:40.820000
 straight through your body
 and into my radio.

0:05:40.820000 --> 0:05:45.400000
 Kind of a strange and freaky thought,
 but that's how it works.

0:05:45.400000 --> 0:05:49.500000
 Now electromagnetic radiation also
 has a detectable waveform.

0:05:49.500000 --> 0:05:54.020000
 It oscillates. And here's sort of a
 way I can sort of paint this picture

0:05:54.020000 --> 0:06:01.680000
 out for you. Imagine that you and I have
 magnets, okay, and we're pointing

0:06:01.680000 --> 0:06:03.280000
 it at each other.

0:06:03.280000 --> 0:06:07.420000
 Now, let's say that you are pointing
 the positive side of your magnet

0:06:07.420000 --> 0:06:14.760000
 towards me. So, if I point my positive
 magnet towards you, there's going

0:06:14.760000 --> 0:06:16.220000
 to be a repulsion, right?

0:06:16.220000 --> 0:06:19.020000
 Because positive to positive sort of
 pushes itself away when it comes

0:06:19.020000 --> 0:06:21.560000
 to magnets. They don't like
 to get close to each other.

0:06:21.560000 --> 0:06:26.080000
 But if I flip my magnet to the negative
 side, now there's going to be

0:06:26.080000 --> 0:06:28.200000
 some attraction between
 our magnets.

0:06:28.200000 --> 0:06:31.420000
 Now, let's say I'm doing that
 over and over and over again.

0:06:31.420000 --> 0:06:34.680000
 Let's say I'm actually doing that billions
 of times per second, positive

0:06:34.680000 --> 0:06:38.080000
 negative, positive negative, positive,
 that would create a waveform, that's

0:06:38.080000 --> 0:06:39.120000
 something you can measure.

0:06:39.120000 --> 0:06:42.980000
 You can measure the strength of the
 positive as it's being pushed away

0:06:42.980000 --> 0:06:46.200000
 from you and the positive decreases
 and now it's the negative as being

0:06:46.200000 --> 0:06:48.120000
 attracted to you.

0:06:48.120000 --> 0:06:50.000000
 And that's a waveform
 that you can measure.

0:06:50.000000 --> 0:06:54.700000
 Similarly, electromagnetic radiation,
 because it has a magnetic component,

0:06:54.700000 --> 0:06:58.840000
 has a waveform that can
 be measured like this.

0:06:58.840000 --> 0:07:03.260000
 And the cycling of this waveform is
 measured in, ta-da, hurts that we

0:07:03.260000 --> 0:07:06.220000
 just talked about.

0:07:06.220000 --> 0:07:11.540000
 So radio frequency is really the measurement
 of the oscillation of electromagnetic

0:07:11.540000 --> 0:07:16.360000
 radiation. Now, the next slide, I'm
 going to go into just a little bit

0:07:16.360000 --> 0:07:21.060000
 of detail to finish off this video because
 there's lots of types of electromagnetic

0:07:21.060000 --> 0:07:27.720000
 radiation and not all of it is technically
 what we would call radio frequency.

0:07:27.720000 --> 0:07:29.300000
 So what's the gamut?

0:07:29.300000 --> 0:07:31.620000
 What's the range of electromagnetic
 radiation?

0:07:31.620000 --> 0:07:37.340000
 Well, some very smart people were out
 there a long time ago and they said,

0:07:37.340000 --> 0:07:42.080000
 you know what? There's electromagnetic
 radiation that barely changes at

0:07:42.080000 --> 0:07:46.900000
 all. That has like a 1 hertz change over
 1 second, it maybe changes barely

0:07:46.900000 --> 0:07:50.420000
 at all. And then there's electromagnetic
 radiation at the far end of the

0:07:50.420000 --> 0:07:55.800000
 scale that changes, you know, trillions
 or gazillions of times per second.

0:07:55.800000 --> 0:07:58.500000
 We should put names to
 that kind of stuff.

0:07:58.500000 --> 0:08:01.480000
 And that's what we see right here.


0:08:01.480000 --> 0:08:07.440000
 So electromagnetic radiation oscillates
 or changes at certain frequencies.

0:08:07.440000 --> 0:08:10.580000
 And these certain, there have been
 bands of frequencies that have been

0:08:10.580000 --> 0:08:13.160000
 given certain labels.

0:08:13.160000 --> 0:08:19.680000
 And the United States Federal Communications
 Commission decided to look

0:08:19.680000 --> 0:08:22.940000
 at some of these bands and assign
 them as what's called ISM bands.

0:08:22.940000 --> 0:08:26.160000
 It stands for Industrial,
 Scientific and Medical.

0:08:26.160000 --> 0:08:29.260000
 Unlicensed bands for Industrial,
 Scientific and Medical Use.

0:08:29.260000 --> 0:08:31.660000
 So let's take a look at this.

0:08:31.660000 --> 0:08:36.720000
 So here we have some electromagnetic
 radiation.

0:08:36.720000 --> 0:08:40.640000
 And depending on the frequency that's
 cycling at, we give it some names.

0:08:40.640000 --> 0:08:42.360000
 For example, there's ELF.

0:08:42.360000 --> 0:08:46.400000
 Yes, the jolly little guy that comes
 with Santa Claus in December time.

0:08:46.400000 --> 0:08:47.900000
 No, that's not what this is.

0:08:47.900000 --> 0:08:50.820000
 This is extremely low frequency.

0:08:50.820000 --> 0:08:53.300000
 And then we have very
 low frequency.

0:08:53.300000 --> 0:08:55.420000
 So for example, what you can hear.


0:08:55.420000 --> 0:08:58.680000
 If you think about your actual ear,
 how does your ear hear anything?

0:08:58.680000 --> 0:09:05.260000
 Well, that's because in this case,
 air is vibrating, which is causing

0:09:05.260000 --> 0:09:07.700000
 your eardrum to vibrate.

0:09:07.700000 --> 0:09:13.140000
 The typical human being, the lowest
 frequency that you can hear is 20

0:09:13.140000 --> 0:09:19.560000
 megahertz. So actually, no, it's 20
 hertz, 20 vibrations in one second.

0:09:19.560000 --> 0:09:23.660000
 That would be a really, really low
 sort of hum that you would hear.

0:09:23.660000 --> 0:09:24.920000
 That's the lowest you can hear.

0:09:24.920000 --> 0:09:28.940000
 And then the highest you can hear, I
 don't remember what that was, what

0:09:28.940000 --> 0:09:32.760000
 that number was, but whatever that range
 of human hearing is, that's what

0:09:32.760000 --> 0:09:35.820000
 falls right in here into
 this audio spectrum.

0:09:35.820000 --> 0:09:38.200000
 Then we have medium.

0:09:38.200000 --> 0:09:40.800000
 We've got medium high
 and very high.

0:09:40.800000 --> 0:09:45.240000
 And if we're talking about electromagnetic
 radiation, we can manipulate

0:09:45.240000 --> 0:09:49.740000
 that for AM broadcast, shortwave
 radio, and broadcast TV.

0:09:49.740000 --> 0:09:55.460000
 Now, if you want to make use of those frequencies,
 you have to get a license.

0:09:55.460000 --> 0:09:59.920000
 You have to go to the FCC, pay them a lot
 of money, get a particular frequency

0:09:59.920000 --> 0:10:04.140000
 that's assigned to you, and now you can
 use that to send out your AM broadcast

0:10:04.140000 --> 0:10:07.220000
 or your broadcast TV
 over the airways.

0:10:07.220000 --> 0:10:12.560000
 Okay, so this is not ISM because,
 no, ISM is unlicensed bands.

0:10:12.560000 --> 0:10:15.040000
 We're not in the ISM bands yet.

0:10:15.040000 --> 0:10:17.100000
 I'm going to skip over something.

0:10:17.100000 --> 0:10:21.060000
 And now as you go into the much higher
 range of electromagnetic radiation,

0:10:21.060000 --> 0:10:24.200000
 we have infrared all the
 way up to gamma rays.

0:10:24.200000 --> 0:10:29.440000
 Now we don't typically use that to encode
 data, although infrared technically

0:10:29.440000 --> 0:10:34.860000
 can be. So for Wi-Fi, we use
 what's missing in the middle.

0:10:34.860000 --> 0:10:36.820000
 So let's take a look at those.

0:10:36.820000 --> 0:10:39.460000
 We have the ultra high range.

0:10:39.460000 --> 0:10:44.300000
 And within the ultra high range, a tiny
 slice of the frequencies within

0:10:44.300000 --> 0:10:50.260000
 that box have been designated as industrial,
 scientific, and medical.

0:10:50.260000 --> 0:10:56.120000
 So you can see here that if you want
 to, you could create a device for

0:10:56.120000 --> 0:11:02.980000
 industrial, scientific, or medical use
 that transmits wirelessly between

0:11:02.980000 --> 0:11:08.500000
 902 and 928 million hertz.

0:11:08.500000 --> 0:11:12.480000
 So within one second, if the frequency
 is rotating or oscillating between

0:11:12.480000 --> 0:11:19.100000
 902 and 928 millions of times megahertz,
 that is an ISM band.

0:11:19.100000 --> 0:11:20.980000
 That does not require a license.

0:11:20.980000 --> 0:11:21.920000
 You don't have to go anywhere.

0:11:21.920000 --> 0:11:23.640000
 You don't have to
 get authorization.

0:11:23.640000 --> 0:11:25.960000
 You can start transmitting
 on that.

0:11:25.960000 --> 0:11:30.280000
 There's another ISM band a little bit
 higher up, which is in the 2.4 to

0:11:30.280000 --> 0:11:33.940000
 2.5 gigahertz. Now remember,
 giga means billions.

0:11:33.940000 --> 0:11:36.660000
 So now we're talking about a device
 that's able to transmit and receive

0:11:36.660000 --> 0:11:39.060000
 using radio frequencies.

0:11:39.060000 --> 0:11:43.260000
 And those radio frequencies are oscillating
 or changing between 2.4 and

0:11:43.260000 --> 0:11:47.560000
 2.5 billions of changes
 per second.

0:11:47.560000 --> 0:11:49.880000
 Within that range, that's
 another ISM band.

0:11:49.880000 --> 0:11:53.280000
 Free to use unlicensed.

0:11:53.280000 --> 0:11:58.480000
 And then we have lastly the super high
 range, which is starting at 5.15

0:11:58.480000 --> 0:12:05.180000
 and going up to 5.875 billions
 of changes per second.

0:12:05.180000 --> 0:12:07.700000
 And this is what's called, this
 is the third ISM range.

0:12:07.700000 --> 0:12:11.500000
 This also has another term, which is
 called UNII, which is the unlicensed

0:12:11.500000 --> 0:12:15.220000
 national information
 infrastructure.

0:12:15.220000 --> 0:12:18.960000
 Now let's talk about each
 one of these ranges here.

0:12:18.960000 --> 0:12:22.040000
 So one thing they all have in common,
 like I've mentioned, is they're

0:12:22.040000 --> 0:12:25.520000
 free. So you can create
 your own radio set.

0:12:25.520000 --> 0:12:30.180000
 You can put your components together,
 your wires and everything else.

0:12:30.180000 --> 0:12:33.440000
 And you can create a radio that will
 transmit and receive at any one of

0:12:33.440000 --> 0:12:34.760000
 these three ranges.

0:12:34.760000 --> 0:12:36.520000
 You're not going to
 be thrown in jail.

0:12:36.520000 --> 0:12:37.860000
 You don't need a license.

0:12:37.860000 --> 0:12:39.520000
 You don't need to go to the FCC.

0:12:39.520000 --> 0:12:44.060000
 It's free. So yay, that's
 kind of cool.

0:12:44.060000 --> 0:12:47.280000
 Now what differentiates these, I mean other
 than the fact that their frequencies

0:12:47.280000 --> 0:12:51.640000
 are getting faster and faster and faster,
 why would I pick one over the

0:12:51.640000 --> 0:12:56.880000
 other? Well, a general rule of thumb
 is when you're encoding data into

0:12:56.880000 --> 0:13:02.180000
 a radio frequency that's changing, the
 faster the frequency of that change,

0:13:02.180000 --> 0:13:06.100000
 the faster the oscillation, the
 more data you can encode.

0:13:06.100000 --> 0:13:10.160000
 So that's why you can see that over
 time as Wi-Fi standards have changed

0:13:10.160000 --> 0:13:14.180000
 and changed and changed, the newest and
 latest and greatest Wi-Fi standards

0:13:14.180000 --> 0:13:18.200000
 are operating more and more costs that
 highest range in the green box,

0:13:18.200000 --> 0:13:20.240000
 the 5 gigahertz frequency range.

0:13:20.240000 --> 0:13:23.580000
 Because between those three different
 boxes there, that's where you can

0:13:23.580000 --> 0:13:26.900000
 get your faster data rates,
 is in the 5 gigahertz range.

0:13:26.900000 --> 0:13:29.200000
 Now you might be thinking, well,
 why doesn't everybody use that?

0:13:29.200000 --> 0:13:32.780000
 Well, there's a downside to it.

0:13:32.780000 --> 0:13:37.500000
 So yes, in the faster the frequency,
 the more data you can encode, but

0:13:37.500000 --> 0:13:38.920000
 here's the problem.

0:13:38.920000 --> 0:13:42.740000
 Radio frequency has a tendency
 to what's called attenuate.

0:13:42.740000 --> 0:13:51.880000
 Attenuate means it changes or more basically
 it, the data that you encode

0:13:51.880000 --> 0:13:54.600000
 becomes unrecognizable.

0:13:54.600000 --> 0:13:57.040000
 Here's an example in the
 world of audio, okay?

0:13:57.040000 --> 0:14:00.140000
 So if you're standing three feet away
 from me and I'm talking at my normal

0:14:00.140000 --> 0:14:02.160000
 voice, you can hear me just fine.

0:14:02.160000 --> 0:14:03.960000
 Now remember, as I'm talking,
 what's going on?

0:14:03.960000 --> 0:14:05.760000
 My vocal cords are vibrating.

0:14:05.760000 --> 0:14:09.720000
 It's vibrating the air that's leaving
 my mouth and that vibration of the

0:14:09.720000 --> 0:14:12.440000
 air is reaching your eardrums.

0:14:12.440000 --> 0:14:16.180000
 However, think about the power
 of the vibration of that air.

0:14:16.180000 --> 0:14:20.080000
 Think about how strong it's
 making your eardrum vibrate.

0:14:20.080000 --> 0:14:22.660000
 If you're standing five feet away
 from me, that's one thing.

0:14:22.660000 --> 0:14:27.140000
 Now if you move back 25 feet away from
 me, you might still be able to

0:14:27.140000 --> 0:14:30.040000
 hear me, but you're not going
 to hear me as well.

0:14:30.040000 --> 0:14:36.020000
 Why is that? That's because the power
 of the airwaves, of the oscillation

0:14:36.020000 --> 0:14:39.920000
 as it's going has diminished
 over distance.

0:14:39.920000 --> 0:14:45.160000
 The farther and farther you get, the airwaves
 that were initially oscillated

0:14:45.160000 --> 0:14:52.380000
 because of my vocal cords will get
 weaker and weaker and weaker.

0:14:52.380000 --> 0:14:56.180000
 The airwaves don't get to you at all,
 or maybe they're so incredibly weak,

0:14:56.180000 --> 0:14:57.880000
 your eardrum doesn't vibrate.

0:14:57.880000 --> 0:14:59.360000
 It doesn't pick up anything.

0:14:59.360000 --> 0:15:03.740000
 The same thing is true with electromagnetic
 radiation, with radio frequencies.

0:15:03.740000 --> 0:15:07.600000
 You may start out with a frequency
 in the real high range there in the

0:15:07.600000 --> 0:15:12.180000
 UNII range, that green box, but the problem
 with those ranges are they're

0:15:12.180000 --> 0:15:13.740000
 sort of short distance.

0:15:13.740000 --> 0:15:18.020000
 You have to be pretty close to the device
 that's initiating that in order

0:15:18.020000 --> 0:15:22.740000
 to pick up those and decode
 those into ones and zeros.

0:15:22.740000 --> 0:15:26.200000
 Whereas at the other end of the spectrum,
 in the ISM range in the blue

0:15:26.200000 --> 0:15:31.220000
 box, in the 900 MHz range, those signals
 can propagate much further.

0:15:31.220000 --> 0:15:34.160000
 They've got much better distance
 characteristics.

0:15:34.160000 --> 0:15:38.880000
 The downside is, they can't
 encode data as fast.

0:15:38.880000 --> 0:15:43.040000
 But all three of those are the ISM ranges,
 and once again the ISM ranges

0:15:43.040000 --> 0:15:48.140000
 just to sort of summarize here are
 certain slices of radio frequencies

0:15:48.140000 --> 0:15:50.700000
 that are free to use.

0:15:50.700000 --> 0:15:57.100000
 The other downside of the ISM range is
 that any device can use this frequency.

0:15:57.100000 --> 0:16:00.740000
 For example, one of the downsides of
 the one there in the middle, the

0:16:00.740000 --> 0:16:02.220000
 2.4 GHz frequency.

0:16:02.220000 --> 0:16:06.360000
 I don't know if this is so much a problem
 these days, but it used to be

0:16:06.360000 --> 0:16:11.580000
 that if you had a Wi-Fi or wireless
 LAN that was using that range, and

0:16:11.580000 --> 0:16:15.980000
 in that wireless LAN BSS and the range
 of the access point was also one

0:16:15.980000 --> 0:16:20.620000
 or more microwaves, a microwave oven
 used to heat up your sandwich, you

0:16:20.620000 --> 0:16:21.340000
 would have a problem.

0:16:21.340000 --> 0:16:25.660000
 Because a lot of microwaves used to
 actually just in how they operated,

0:16:25.660000 --> 0:16:29.040000
 I don't know the mechanics of this,
 but in how they operated when you

0:16:29.040000 --> 0:16:33.500000
 turned them on, they would actually
 induce noise that was in this range.

0:16:33.500000 --> 0:16:37.160000
 That was in the 2.4 GHz range, so a
 microwave would actually impede your

0:16:37.160000 --> 0:16:40.740000
 signal. Your Wi-Fi signal would just
 degrade or maybe go all the way down

0:16:40.740000 --> 0:16:43.380000
 if you had a microwave operating.

0:16:43.380000 --> 0:16:48.120000
 And so that's the downside of using
 the ISM bands, is that anybody can

0:16:48.120000 --> 0:16:53.500000
 create any device that either intentionally
 or unintentionally uses the

0:16:53.500000 --> 0:16:58.000000
 same frequency, and it might step on
 the toes of what you're doing in

0:16:58.000000 --> 0:16:59.020000
 the exact same band.

0:16:59.020000 --> 0:17:00.600000
 There's nobody regulating it.

0:17:00.600000 --> 0:17:04.260000
 There's nobody that's saying, okay,
 you can get 2.5, you can get 2.67,

0:17:04.260000 --> 0:17:06.180000
 and that's yours only to use.

0:17:06.180000 --> 0:17:07.060000
 Nobody's doing that.

0:17:07.060000 --> 0:17:09.160000
 It's free and it's unlicensed.

0:17:09.160000 --> 0:17:14.200000
 But in the world of Wi-Fi, Wi-Fi has
 chosen to use these because let's

0:17:14.200000 --> 0:17:18.120000
 face it, it's a lot cheaper from manufacturer
 to create millions of access

0:17:18.120000 --> 0:17:23.320000
 points and clients with radios that
 don't have to be licensed versus you

0:17:23.320000 --> 0:17:26.360000
 want to go into business operating
 your own television station.

0:17:26.360000 --> 0:17:28.980000
 Well, yeah, you might buy your own
 cameras and transmitters and stuff,

0:17:28.980000 --> 0:17:32.900000
 but now you got to go to the FCC and
 give them a lot of money to purchase

0:17:32.900000 --> 0:17:36.760000
 a certain frequency range that you
 can use for your TV station to make

0:17:36.760000 --> 0:17:41.860000
 sure that other people
 don't step on the toes.

0:17:41.860000 --> 0:17:47.340000
 So that is what the ISM bands are all
 about, and that concludes this video.

0:17:47.340000 --> 0:17:50.300000
 So thank you very much for watching,
 and I hope you found it useful.