1 1 00:00:00,420 --> 00:00:02,370 Depending on the coverage area you have, 2 2 00:00:02,370 --> 00:00:04,340 it's really going to determine the type of antenna 3 3 00:00:04,340 --> 00:00:07,810 that you want to use inside your home or your small office. 4 4 00:00:07,810 --> 00:00:09,870 You're probably using a standard fixed antenna 5 5 00:00:09,870 --> 00:00:11,510 on your wireless access point. 6 6 00:00:11,510 --> 00:00:12,750 But when you start designing things 7 7 00:00:12,750 --> 00:00:14,230 for an enterprise network, 8 8 00:00:14,230 --> 00:00:16,250 you're going to start choosing the right antenna 9 9 00:00:16,250 --> 00:00:17,680 for the right job. 10 10 00:00:17,680 --> 00:00:18,930 Now, there are different factors 11 11 00:00:18,930 --> 00:00:20,480 that will help you determine the effectiveness 12 12 00:00:20,480 --> 00:00:21,313 of your antenna, 13 13 00:00:21,313 --> 00:00:23,000 including the distance you want to cover, 14 14 00:00:23,000 --> 00:00:25,120 the pattern of the wireless coverage you need, 15 15 00:00:25,120 --> 00:00:26,520 and the environment itself, 16 16 00:00:26,520 --> 00:00:28,660 whether it's inside or outside. 17 17 00:00:28,660 --> 00:00:31,440 If you want to avoid interference with other access points, 18 18 00:00:31,440 --> 00:00:33,510 all of these things go into your decision making 19 19 00:00:33,510 --> 00:00:35,850 when determining the right antenna to use. 20 20 00:00:35,850 --> 00:00:37,320 The most commonly used antenna 21 21 00:00:37,320 --> 00:00:39,240 is an omnidirectional antenna. 22 22 00:00:39,240 --> 00:00:41,280 The way it works is it's either built in 23 23 00:00:41,280 --> 00:00:44,330 or a fixed antenna on your wireless access point. 24 24 00:00:44,330 --> 00:00:46,090 It's going to radiate power out equally 25 25 00:00:46,090 --> 00:00:47,830 in every single direction. 26 26 00:00:47,830 --> 00:00:50,040 And so if you're using an omnidirectional antenna, 27 27 00:00:50,040 --> 00:00:52,630 it's usually best to place your access point right 28 28 00:00:52,630 --> 00:00:54,160 in the center of your room. 29 29 00:00:54,160 --> 00:00:56,010 If you go to a college classroom, for instance, 30 30 00:00:56,010 --> 00:00:57,920 and you look up in the center of the classroom, 31 31 00:00:57,920 --> 00:00:59,600 you may see a wireless antenna 32 32 00:00:59,600 --> 00:01:02,040 that's omnidirectional, sitting on the ceiling, 33 33 00:01:02,040 --> 00:01:05,050 providing full coverage to that entire classroom. 34 34 00:01:05,050 --> 00:01:05,883 In your home, 35 35 00:01:05,883 --> 00:01:07,940 if you have a Verizon or a Comcast 36 36 00:01:07,940 --> 00:01:09,660 or another cable service provider, 37 37 00:01:09,660 --> 00:01:11,870 and they give you one of those all-in-one devices 38 38 00:01:11,870 --> 00:01:14,240 with the wireless router configuration, 39 39 00:01:14,240 --> 00:01:16,220 these have an omnidirectional antenna 40 40 00:01:16,220 --> 00:01:18,930 that go out in every single direction. 41 41 00:01:18,930 --> 00:01:20,380 The next one we have is what's known 42 42 00:01:20,380 --> 00:01:22,180 as a unidirectional antenna. 43 43 00:01:22,180 --> 00:01:24,030 Now, uni means one. 44 44 00:01:24,030 --> 00:01:25,850 So all the power is being focused out 45 45 00:01:25,850 --> 00:01:27,730 in one particular direction. 46 46 00:01:27,730 --> 00:01:28,810 And most common, 47 47 00:01:28,810 --> 00:01:31,290 your unidirectional antenna is going to be something known 48 48 00:01:31,290 --> 00:01:32,710 as a Yagi antenna. 49 49 00:01:32,710 --> 00:01:35,210 That's spelled Y-A-G-I. 50 50 00:01:35,210 --> 00:01:37,940 Now, I have one here displayed for you on the screen. 51 51 00:01:37,940 --> 00:01:40,110 The most common use of a Yagi antenna 52 52 00:01:40,110 --> 00:01:42,880 is when you want to put out power over a longer distance 53 53 00:01:42,880 --> 00:01:46,330 and connect buildings to other buildings or to other sites. 54 54 00:01:46,330 --> 00:01:48,200 We might put two wireless access points 55 55 00:01:48,200 --> 00:01:50,580 on the top of a building, point them at each other, 56 56 00:01:50,580 --> 00:01:53,100 and use a Yagi antenna that's pointed directly 57 57 00:01:53,100 --> 00:01:55,800 at the other one to maintain that connection. 58 58 00:01:55,800 --> 00:01:57,830 In this example here, I have two buildings 59 59 00:01:57,830 --> 00:02:00,200 and you'll see strong blue radio waves going 60 60 00:02:00,200 --> 00:02:01,370 between the two. 61 61 00:02:01,370 --> 00:02:03,160 You'll notice that there's not much waves going out 62 62 00:02:03,160 --> 00:02:05,260 the other side from the other direction. 63 63 00:02:05,260 --> 00:02:06,610 That's because of the Yagi, 64 64 00:02:06,610 --> 00:02:07,800 we're really focusing 65 65 00:02:07,800 --> 00:02:10,500 and putting all that power out a single direction 66 66 00:02:10,500 --> 00:02:12,860 because it is a unidirectional antenna. 67 67 00:02:12,860 --> 00:02:15,360 Now, where else might you find directional antennas? 68 68 00:02:15,360 --> 00:02:16,570 Well, if I'm trying to provide 69 69 00:02:16,570 --> 00:02:18,320 a wireless network inside a building 70 70 00:02:18,320 --> 00:02:19,900 and on the inside of the building 71 71 00:02:19,900 --> 00:02:21,780 I want to use unidirectional antennas 72 72 00:02:21,780 --> 00:02:24,930 to shape the direction of where I want that power to go. 73 73 00:02:24,930 --> 00:02:27,850 This way, instead of going out equally in all directions, 74 74 00:02:27,850 --> 00:02:30,170 I can focus it in a particular direction 75 75 00:02:30,170 --> 00:02:32,730 and ensure that I'm not having my wireless signal go out 76 76 00:02:32,730 --> 00:02:34,170 and bleed into the parking lot, 77 77 00:02:34,170 --> 00:02:36,790 and that way it's not going out as a security risk. 78 78 00:02:36,790 --> 00:02:39,340 Going back to the heat map we had in the previous lesson, 79 79 00:02:39,340 --> 00:02:41,810 you can see where this can become really important. 80 80 00:02:41,810 --> 00:02:43,150 Now, for the exam, 81 81 00:02:43,150 --> 00:02:46,110 you may get something like a picture of a floor plan 82 82 00:02:46,110 --> 00:02:47,950 and be asked to pick which antennas 83 83 00:02:47,950 --> 00:02:49,400 should go in which places. 84 84 00:02:49,400 --> 00:02:51,510 And so maybe you're going to put in three or five 85 85 00:02:51,510 --> 00:02:52,800 or 10 different antennas. 86 86 00:02:52,800 --> 00:02:54,250 And you might have to decide if you're going to put 87 87 00:02:54,250 --> 00:02:56,700 a left directional antenna in on a right wall. 88 88 00:02:56,700 --> 00:02:58,890 So you're keeping the signal inside the building. 89 89 00:02:58,890 --> 00:03:01,350 Or, a right directional antenna on the left wall. 90 90 00:03:01,350 --> 00:03:03,230 Again, keeping it inside the building. 91 91 00:03:03,230 --> 00:03:05,800 If you're in the center, you want an omnidirectional. 92 92 00:03:05,800 --> 00:03:07,720 If you want to connect one building to another, 93 93 00:03:07,720 --> 00:03:10,230 you might use something like a Yagi antenna on the roof 94 94 00:03:10,230 --> 00:03:11,770 to point that to another building 95 95 00:03:11,770 --> 00:03:13,470 and keep it directional as well. 96 96 00:03:13,470 --> 00:03:15,110 These are the kind of things you need to think about 97 97 00:03:15,110 --> 00:03:17,210 as you're picking your antennas for the case 98 98 00:03:17,210 --> 00:03:18,043 that you're doing 99 99 00:03:18,043 --> 00:03:19,620 and whatever scenario they give you.