-: Depending on the coverage area you have, 2 2
it's really going to determine the type of antenna 3 3
that you want to use inside your home or your small office. 4 4
You're probably using a standard fixed antenna 5 5
on your wireless access point. 6 6
But when you start designing things 7 7
for an enterprise network, 8 8
you're going to start choosing the right antenna 9 9
for the right job. 10 10
Now, there are different factors 11 11
that will help you determine the effectiveness 12 12
of your antenna, 13 13
including the distance you want to cover, 14 14
the pattern of the wireless coverage you need, 15 15
and the environment itself, 16 16
whether it's inside or outside. 17 17
If you want to avoid interference with other access points, 18 18
all of these things go into your decision making 19 19
when determining the right antenna to use. 20 20
The most commonly used antenna 21 21
is an omnidirectional antenna. 22 22
The way it works is it's either built in 23 23
or a fixed antenna on your wireless access point. 24 24
It's going to radiate power out equally 25 25
in every single direction. 26 26
And so if you're using an omnidirectional antenna, 27 27
it's usually best to place your access point right 28 28
in the center of your room. 29 29
If you go to a college classroom, for instance, 30 30
and you look up in the center of the classroom, 31 31
you may see a wireless antenna 32 32
that's omnidirectional, sitting on the ceiling, 33 33
providing full coverage to that entire classroom. 34 34
In your home, 35 35
if you have a Verizon or a Comcast 36 36
or another cable service provider, 37 37
and they give you one of those all-in-one devices 38 38
with the wireless router configuration, 39 39
these have an omnidirectional antenna 40 40
that go out in every single direction. 41 41
The next one we have is what's known 42 42
as a unidirectional antenna. 43 43
Now, uni means one. 44 44
So all the power is being focused out 45 45
in one particular direction. 46 46
And most common, 47 47
your unidirectional antenna is going to be something known 48 48
as a Yagi antenna. 49 49
That's spelled Y-A-G-I. 50 50
Now, I have one here displayed for you on the screen. 51 51
The most common use of a Yagi antenna 52 52
is when you want to put out power over a longer distance 53 53
and connect buildings to other buildings or to other sites. 54 54
We might put two wireless access points 55 55
on the top of a building, point them at each other, 56 56
and use a Yagi antenna that's pointed directly 57 57
at the other one to maintain that connection. 58 58
In this example here, I have two buildings 59 59
and you'll see strong blue radio waves going 60 60
between the two. 61 61
You'll notice that there's not much waves going out 62 62
the other side from the other direction. 63 63
That's because of the Yagi, 64 64
we're really focusing 65 65
and putting all that power out a single direction 66 66
because it is a unidirectional antenna. 67 67
Now, where else might you find directional antennas? 68 68
Well, if I'm trying to provide 69 69
a wireless network inside a building 70 70
and on the inside of the building 71 71
I want to use unidirectional antennas 72 72
to shape the direction of where I want that power to go. 73 73
This way, instead of going out equally in all directions, 74 74
I can focus it in a particular direction 75 75
and ensure that I'm not having my wireless signal go out 76 76
and bleed into the parking lot, 77 77
and that way it's not going out as a security risk. 78 78
Going back to the heat map we had in the previous lesson, 79 79
you can see where this can become really important. 80 80
Now, for the exam, 81 81
you may get something like a picture of a floor plan 82 82
and be asked to pick which antennas 83 83
should go in which places. 84 84
And so maybe you're going to put in three or five 85 85
or 10 different antennas. 86 86
And you might have to decide if you're going to put 87 87
a left directional antenna in on a right wall. 88 88
So you're keeping the signal inside the building. 89 89
Or, a right directional antenna on the left wall. 90 90
Again, keeping it inside the building. 91 91
If you're in the center, you want an omnidirectional. 92 92
If you want to connect one building to another, 93 93
you might use something like a Yagi antenna on the roof 94 94
to point that to another building 95 95
and keep it directional as well. 96 96
These are the kind of things you need to think about 97 97
as you're picking your antennas for the case 98 98
that you're doing 99 99
and whatever scenario they give you.