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 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 analogue radio.
Explain concepts such as channels or radio stations to use the analogue radio station term or channels
in Wi-Fi and also to explain frequencies which will help you understand why five gigahertz is better
than 2.5 gigahertz as in it's better at transmitting more data but does have other disadvantages.
Now I've mentioned 2.5 gigahertz and 5 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 Salih 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 5 gigahertz especially around airports on a traditional radio
like this or a radio in your car you may have F.M. or am so different frequencies are used by F.M. 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 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 ninety four point two F.M. is their radio station.
If you or one 0 3 something depending on where you on 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 there 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 will do as you moving is it will switch to another access point that's broadcasting
the same SS I.D. as this I.D. 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 SS I.D. 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 1 has been designated as 5 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 2.5 gigahertz SS I.D. or network that I'm connecting to.
So service set identifiers or SS I.D. allow us to know the name of a Wi-Fi network an iPhone moving
around.
We'll 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 SSD.
This radio supports frequency modulation or F.M..
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 F.M. we've got 88 to 1 0 8 megahertz medium way we've got 540 to 1600 and long wave we've got
150 to two 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 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.
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 is tuned to that specific frequency which allows me to listen to that radio station.
Same concept exists in Wi-Fi Wi-Fi uses different frequencies.
The two main frequencies that you need to be concerned with are 2.5 gigahertz and 5 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 2.5 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 2.5 gigahertz range here we've got specific channels and
the channels that we are most concerned with is Channel 1 6 and 11 these two channels 1 6 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 asks was transmitting on this channel they would be bleeding into your channel and and here
would be over talking each other or talking across one another reducing our transmission.
So typically you want to use six eleven 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 1 and you were using Channel 2 we would be over talking each other
and reducing our throughput.