Now for some of the wi fi explanations, I'm going to be using an analogue radio, old analogue radio.
And you may be asking, David, I don't care about analog radios, but remember, wi fi is using wireless
technologies just like this is.
This uses different frequencies, but it's also using the air in a similar way to wi fi.
And I'm going to be using this to demonstrate a concept which is Hertz or cycles per second.
This has got kilohertz, megahertz, wi fi, we've got gigahertz.
So it's well worth spending a little bit of time using an analog radio explained concepts such as channels
or radio stations to use the analog radio station term or channels in wi fi, and also to explain frequencies
which will help you understand why five gigahertz is better than 2.4 gigahertz, as in it's better at
transmitting more data but does have other disadvantages.
I've mentioned 2.4 gigahertz and five gigahertz frequencies quite a bit now.
So let's explain what that is.
And to help us with an analogy here, I've got an old style radio.
On a radio like this.
We will have different frequency ranges.
Now, again, governments around the world dictate the frequencies and what they can be used for.
So there's a frequency spectrum.
Phones, as an example, have different radios inside of them.
So I can connect to the cellular network, or I can connect to the wi fi network.
So if you're in a plane as an example, you'll be told to turn off your cellular network.
But you can use the wi fi connection.
Different radios, different frequencies are used.
Some frequencies will interfere with other devices.
So as an example, some of the five gigahertz frequencies interfere with radar.
So when you're near an airport, you have to turn off those frequencies you're not allowed to use in
some countries, certain frequencies, such as five gigahertz, especially around airport.
On a traditional radio like this or a radio in your car, you may have FM or AM.
So different frequencies are used by FM or AM on a traditional radio, and this is obviously an old
style radio.
When I turn this on, I might hear nothing.
So hopefully you can hear that all I hear is white noise because I'm not tuned in to a radio station.
Now we talk about a radio station, but actually all a radio station is is me tuning the dial until
I'm listening in on a specific frequency.
Now, a lot of us will talk about a radio station rather than a specific frequency.
Some radio stations, as an example, will say 94.2 FM is their radio station.
If you or one, two, three something depending on where you are in the world, different radio stations
will broadcast or transmit on a specific frequency, and you will get different radio stations depending
where you are.
You might have had this experience if you're driving long distance when you're driving and your radio
set to a specific frequency or specific channel to use a wi fi term when you drive.
At some point, the there's interference where you can hear two radio stations and then one will slowly
get quieter and one will get louder.
And then eventually you'll only hear the one radio station.
So the idea there is think of this as two wi fi antennas, but this is in radio terms, we've got two
antennas broadcasting and as you driving the signal from one gets weaker and weaker while the signal
from the other gets stronger and stronger, and eventually you'll switch from one to the other.
Your wi fi device, like your iPhone, will do something very similar.
If it's moving through a enterprise network where they've got multiple antennas, it will associate
to the one that's transmitting with the greatest power.
And as you move away from that one, it will hear another one.
And then what it'll do as you're moving is it will switch to another access point that's broadcasting
the same SSID.
It's this ID is a identifier for a wireless network.
You've probably seen it many, many times on your wi fi device on this phone.
As an example, if I go to wi fi connections, I can see different SSIDs or service set identifiers.
These identify different wi fi networks that I can connect to and I can jump from one wi fi network
to another.
In this example, ABC one has been designated as five gigahertz.
Just to make it easy for me to know that that's a five gigahertz network, but I could select ABC one.
This is one of my wi fi networks.
I know that that's a 2.4 gigahertz SSID or network that I'm connecting to.
So service said identifiers or SSIDs allow us to know the name of a wi fi network.
An iPhone moving around will try and associate with an access point or a device that's broadcasting
with the most power.
And then as that gets quieter, it will associate automatically with another access point that's broadcasting
the same SSID.
This radio supports frequency modulation or FM.
We've got medium wave and we've got long wave on this radio.
And what you'll notice is the frequencies differ.
So for FM we've got 88 to 108 megahertz medium wave, we've got 540 to 1600 and long wave, we've got
152 to 80 kilohertz.
And I'll explain kilohertz, megahertz gigahertz in a moment.
But the point is, is that different frequencies are used in the air for transmitting different signals.
But within this range of frequencies, I can tune my radio to a specific radio station on that frequency
when it's not tuned to a radio station.
All I hear is white noise, something like this.
But as I tune the dial on the radio, I'll hear a radio station take me to a different place.
Just a.
I have to be careful because of copyright recording some of these channels or radio stations.
Notice the term a radio station is actually just me tuning the radio to a specific channel or to a specific
frequency within a range.
So different radio stations broadcast on specific frequencies or specific channels to use a wi fi term.
And then I tune or listen in on a specific radio station.
So my radio is tuned to that specific frequency which allows me to listen to that radio station.
Same concept exists in wi fi.
WiFi uses different frequencies.
The two main frequencies that you need to be concerned with are 2.4 gigahertz and five gigahertz.
Notice this is gigahertz, not megahertz or kilohertz, different frequency range, because once again,
governments decide which frequencies are allocated to which applications.
So 2.4 gigahertz is actually this range of frequencies.
But within that range, I would tune to a specific channel to listen in on a specific radio transmission
or basically to be connected to a specific access point or specific device.
Five gigahertz is in this range.
It's broken up into these specific ranges.
But, you know, PowerPoint slides are really boring.
I don't like PowerPoint slides.
I much prefer showing you stuff practically.
So let's have a look at these frequencies practically before we get there.
I just want to point out that notice in the 2.4 gigahertz range here, we've got specific channels,
and the channels that we are most concerned with is channel one, six and 11.
These two channels, one, six and 11 are the channels that you should be using so that you don't have
overlapping transmissions with other devices in the same frequency range.
When you send a transmission on this channel, it's actually bleeding in to the other frequencies.
So it's not just here, it's bleeding across a certain range of frequencies.
If someone else was transmitting on this channel, they would be bleeding into your channel.
And and here we'd be over talking each other or talking across one another, reducing our transmission.
So typically you want to use six, 11 and one so that there is a gap between your transmission so that
you're not talking over one another.
So once again, if I was using Channel one and you were using Channel two, we would be over talking
each other and reducing our throughput.