So in this lesson, I wanted to show you
what some of these antennas look like with more
of a hands-on approach.
So let's go ahead
and start with what's called an omnidirectional antenna.
And this is what you have in most
of your wireless access points
and most of your wireless devices.
So if I take for instance, this old cell phone,
this old cell phone has a wifi connection
inside of it built in.
It actually is an Android cell phone,
and it has the ability to either receive a wireless signal
through wifi or put one out as a hotspot
and then allow other devices to connect through wifi to it
and then go out through its cellular connection
to get access to the internet.
Now, you'll notice when I was talking about this cell phone,
I mentioned its omnidirectional,
and that makes sense for a cell phone
because as you're walking around,
you don't know which direction
the signal's going to be coming from.
So instead, it's going to send and receive data,
both up and down, left and right, forward and back
in every single direction with equal power
to be able to connect to the local wireless access point
or the local cellular tower, depending on
which frequencies we're using.
Now, this is the same thing that happens
with your wireless access points too.
So for instance, if I take this old wireless access point
from Netgear, you'll see this is actually a combination
device of a router, a switch,
as well as a wireless access point,
there's no external antenna.
Instead they're using an internal omnidirectional antenna
just like that cell phone did.
And so in every single direction,
we're going to be sending data out to be able
to get data out equally in all directions.
So if I want to make sure that this doesn't bleed over,
if I'm in a townhouse or an apartment,
for instance, I'd want to put it closer
to the center of my apartment
because if I put it on one of the walls,
it's going to go out in every direction, including
through the wall and into my neighbor's apartment.
And so you might want to consider
that from a security perspective.
Now, some of the more expensive wireless devices are going to
give you the ability to change out your antenna.
So for example, we talked earlier about this combination
device that I got from Verizon,
and inside this one, we did have the ability
to connect a different antenna.
So normally it's going to come with an antenna like this,
which is a standard little whip antenna,
and this is considered an omnidirectional antenna.
So as I connect that on there, I'm going to be able
to send data out in every direction, all 360 degrees.
Now this is a rather small antenna,
so it's not going to have as much power.
Maybe I wanted to get my signal to go out further.
Well, I can actually change that
and I can take that antenna off
and I can put on a bigger antenna.
And with the bigger antenna, I'm actually going to be able
to send data out a little bit further than I could before
because the longer the antenna,
the more propagation you're going to get for it.
Now also, when I'm doing wireless attacks
and wireless hacking and pen tests,
I actually have a wireless card that I use with my laptop
and that has the ability for me
to change the antenna as well.
And so I would take this wireless card
and I would screw on whichever antenna I want.
So if I want more distance or more power, I can go ahead
and use an omnidirectional antenna like this, screw it on,
connect this through USB, back to my laptop,
and now I have this antenna radiating out
in every direction.
Now, I've spent a lot of time talking about omnidirectional
antennas, but what do you do if you want
to make it go in a single direction?
For example, when I'm doing wireless pen testing,
often omnidirectional is not the best way to go
because when you're putting power out in all directions,
you're limited in how far you can go.
But if I can focus my power in just one direction,
that's called unidirectional,
I can actually focus all the power out the left side
of the antenna or the right side of the antenna.
And that way I can push all of the power one way
and no signal goes out the other.
That's using a unidirectional antenna.
And we have unidirectional left,
unidirectional right and things like that.
So we could choose which direction we're going to be using.
Now, the other thing when we were dealing with antennas
you have to think about is what are some of the other types
of antennas that are out there
besides the standard unidirectional
and omnidirectional, uni, meaning one, omni meaning all,
we also have things known as parabolic.
Now, parabolic are a special type of unidirectional.
Parabolic is going to give it a different curvature
to the way the signal's going to go out,
and it's most often used with microwave signals
as well as satellite TV signals
as you can see here on this particular antenna.
Now, this is a direct TV antenna on one
of my neighbor's houses that I drove by
and took a picture of for you.
And you can see that curvature of the dish, which is going
to focus the energy up and towards the satellite
and not out in every other direction.
Finally, I want you to consider this other antenna here.
This one is actually in the UHF band,
which is a frequency band that we use.
And it used to be used a lot for tv
before we had cable, you'd have UHF and VHF.
Now with this antenna, you can also see
that it is a very directional antenna.
You could see how it's pointing in one direction,
almost like an arrow, that's going to allow it
to get a further reach to that signal,
to that TV transmitter that's sending it out.
Now, do we use these anymore?
Well, sometimes.
These actually can be used to point
and push a wireless signal over a longer distance.
So if you're in a business park
or a campus setting, you might see some
of these antennas on top
of buildings pointing from one building
to the other using this unidirectional antenna.
In this case, this is actually known as a Yagi antenna,
Y-A-G-I, and it allows them to have a very directional
focused beam going from one building to another.
So if you hear the term Yagi, that is going to be something
that is a directional antenna,
unidirectional antenna going one way.
Now, if you hear about parabolic, I want you to think about
that satellite TV, that curved dish that's pointing
that directional back towards the satellite.
And if you think about omnidirectional, I want you
to think about these embedded devices,
things like your wireless access point
or things like your cell phone
or things like your wireless card with a long antenna.
This is just the idea.
There's different types of antennas
used for different situations.
It all depends on what you're going to do.
Now for the exam, you want to be able
to know when you should use an omnidirectional antenna
or when you should use a directional antenna,
or when you should use something that attaches to the side
of a building like Apache antenna,
which is a small circular dish that is able
to go on one side of the building to another,
and they can point at each other in a directional manner.
These are different types of antennas
that you may come across when dealing
with wireless networks, and they're important to understand
before you take the exam.