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So in this lesson, I wanted to show you

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what some of these antennas look like with more

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of a hands-on approach.

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So let's go ahead

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and start with what's called an omnidirectional antenna.

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And this is what you have in most

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of your wireless access points

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and most of your wireless devices.

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So if I take for instance, this old cell phone,

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this old cell phone has a wifi connection

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inside of it built in.

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It actually is an Android cell phone,

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and it has the ability to either receive a wireless signal

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through wifi or put one out as a hotspot

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and then allow other devices to connect through wifi to it

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and then go out through its cellular connection

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to get access to the internet.

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Now, you'll notice when I was talking about this cell phone,

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I mentioned its omnidirectional,

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and that makes sense for a cell phone

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because as you're walking around,

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you don't know which direction

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the signal's going to be coming from.

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So instead, it's going to send and receive data,

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both up and down, left and right, forward and back

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in every single direction with equal power

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to be able to connect to the local wireless access point

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or the local cellular tower, depending on

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which frequencies we're using.

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Now, this is the same thing that happens

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with your wireless access points too.

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So for instance, if I take this old wireless access point

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from Netgear, you'll see this is actually a combination

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device of a router, a switch,

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as well as a wireless access point,

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there's no external antenna.

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Instead they're using an internal omnidirectional antenna

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just like that cell phone did.

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And so in every single direction,

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we're going to be sending data out to be able

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to get data out equally in all directions.

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So if I want to make sure that this doesn't bleed over,

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if I'm in a townhouse or an apartment,

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for instance, I'd want to put it closer

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to the center of my apartment

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because if I put it on one of the walls,

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it's going to go out in every direction, including

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through the wall and into my neighbor's apartment.

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And so you might want to consider

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that from a security perspective.

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Now, some of the more expensive wireless devices are going to

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give you the ability to change out your antenna.

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So for example, we talked earlier about this combination

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device that I got from Verizon,

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and inside this one, we did have the ability

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to connect a different antenna.

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So normally it's going to come with an antenna like this,

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which is a standard little whip antenna,

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and this is considered an omnidirectional antenna.

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So as I connect that on there, I'm going to be able

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to send data out in every direction, all 360 degrees.

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Now this is a rather small antenna,

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so it's not going to have as much power.

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Maybe I wanted to get my signal to go out further.

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Well, I can actually change that

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and I can take that antenna off

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and I can put on a bigger antenna.

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And with the bigger antenna, I'm actually going to be able

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to send data out a little bit further than I could before

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because the longer the antenna,

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the more propagation you're going to get for it.

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Now also, when I'm doing wireless attacks

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and wireless hacking and pen tests,

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I actually have a wireless card that I use with my laptop

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and that has the ability for me

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to change the antenna as well.

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And so I would take this wireless card

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and I would screw on whichever antenna I want.

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So if I want more distance or more power, I can go ahead

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and use an omnidirectional antenna like this, screw it on,

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connect this through USB, back to my laptop,

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and now I have this antenna radiating out

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in every direction.

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Now, I've spent a lot of time talking about omnidirectional

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antennas, but what do you do if you want

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to make it go in a single direction?

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For example, when I'm doing wireless pen testing,

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often omnidirectional is not the best way to go

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because when you're putting power out in all directions,

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you're limited in how far you can go.

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But if I can focus my power in just one direction,

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that's called unidirectional,

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I can actually focus all the power out the left side

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of the antenna or the right side of the antenna.

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And that way I can push all of the power one way

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and no signal goes out the other.

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That's using a unidirectional antenna.

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And we have unidirectional left,

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unidirectional right and things like that.

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So we could choose which direction we're going to be using.

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Now, the other thing when we were dealing with antennas

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you have to think about is what are some of the other types

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of antennas that are out there

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besides the standard unidirectional

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and omnidirectional, uni, meaning one, omni meaning all,

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we also have things known as parabolic.

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Now, parabolic are a special type of unidirectional.

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Parabolic is going to give it a different curvature

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to the way the signal's going to go out,

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and it's most often used with microwave signals

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as well as satellite TV signals

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as you can see here on this particular antenna.

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Now, this is a direct TV antenna on one

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of my neighbor's houses that I drove by

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and took a picture of for you.

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And you can see that curvature of the dish, which is going

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to focus the energy up and towards the satellite

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and not out in every other direction.

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Finally, I want you to consider this other antenna here.

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This one is actually in the UHF band,

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which is a frequency band that we use.

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And it used to be used a lot for tv

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before we had cable, you'd have UHF and VHF.

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Now with this antenna, you can also see

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that it is a very directional antenna.

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You could see how it's pointing in one direction,

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almost like an arrow, that's going to allow it

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to get a further reach to that signal,

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to that TV transmitter that's sending it out.

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Now, do we use these anymore?

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Well, sometimes.

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These actually can be used to point

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and push a wireless signal over a longer distance.

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So if you're in a business park

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or a campus setting, you might see some

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of these antennas on top

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of buildings pointing from one building

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to the other using this unidirectional antenna.

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In this case, this is actually known as a Yagi antenna,

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Y-A-G-I, and it allows them to have a very directional

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focused beam going from one building to another.

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So if you hear the term Yagi, that is going to be something

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that is a directional antenna,

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unidirectional antenna going one way.

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Now, if you hear about parabolic, I want you to think about

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that satellite TV, that curved dish that's pointing

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that directional back towards the satellite.

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And if you think about omnidirectional, I want you

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to think about these embedded devices,

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things like your wireless access point

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or things like your cell phone

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or things like your wireless card with a long antenna.

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This is just the idea.

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There's different types of antennas

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used for different situations.

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It all depends on what you're going to do.

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Now for the exam, you want to be able

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to know when you should use an omnidirectional antenna

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or when you should use a directional antenna,

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or when you should use something that attaches to the side

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of a building like Apache antenna,

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which is a small circular dish that is able

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to go on one side of the building to another,

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and they can point at each other in a directional manner.

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These are different types of antennas

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that you may come across when dealing

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with wireless networks, and they're important to understand

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before you take the exam.