Wireless Radio Patterns

Nathan explains antennae placement and wireless radio patterns, including omni-directional and yagi/directional patterns.

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Hello, my name is Nathan and thank you for joining us today. Today, we're going to be talking about wireless radio patterns. As exciting as that sounds, hopefully we'll be able to learn something from this today. I get a lot of questions about this, even just from natural conversation about placement of antennas, where is it make sense, where does it not make sense, how much bleed through, and walls and ceilings. We'll talk a little bit about that today.

The first antenna that I chose to talk about was omnidirectional or omni for short. This is probably the most common. Sure, there are directional antennas which we will get into for bridging, but omni is this kind of the bread and butter of wireless. It's what most folks are using in their environment, so this covers much area as possible.

If we take a look at these radiating patterns, and no this is not a poorly made doughnut. It is a poorly made drawing though. Here in the center, this little box is going to be the access point. You see that from above, if you were to look at that radiating pattern, it looks like a giant circle.

Your vendors may differ, your mileage may vary as far as what that radiating pattern will look like but it almost always, it's just a big circle. The reason for that, just like we said, we're trying to cover as much area as possible. If you were to hang this AP on the ceiling and look down on it, you're going to see that it's trying to cover as much area as it can. That range will change depending on the antenna, how many dBi or the strength of the antenna and even just the access points itself from what it's capable of doing.

This pattern changes greatly when you look at it from the side. Same access point, but from the side, it looks like it has two giant ears. What that is is that all around that antenna is where the pattern radiates, but directly above and directly below, the signal is much ... I wouldn't say weaker, but the coverage is just isn't there and it's just how the radios work.

Where would that matter? A big place it would matter is if you imagine that you had a ceiling here, that this AP was hanging on, some of that signal is going to bleed through potentially upstairs. Maybe there is nothing upstairs, so maybe that wouldn't matter or maybe the flooring is thick enough that it won't bleed as much but still a consideration.

If you were to have an AP here and then say on the floor above another AP, how do those radiating patterns interfere with one another or overlap, it's absolutely a consideration. If you ever stood underneath an access point directly and wondered why you weren't getting a great signal, it's probably because you were sort of in this little hole like the eye of the storm there that takes place right underneath that antenna.

Hopefully, it gives you a better idea of how those would work and how that can impact maybe the performance of your wireless network.

Over here, we have the Yagi or directional antenna. This is very crude as well and you'll see that as you start looking through antennas, if you start looking at radiating patterns for those antennas that these shapes will vary greatly.

Some of your dish antennas will actually have a very, very sharper, thin and narrow signal both from above and below or from the side and above to just show you how far reaching their range is. It's more of a very focused beam.

Here, looking more of a Yagi style, from above, you'll see that that radiating pattern does not go all the way around the antenna, but instead it goes out almost in a cone shape and covers more of an oval in the area. Again, that radius or how much of coverage area that will cover is really based on the antenna and the access point that's involved.

This is where you would have more of a directional focus if you had a specialized location like maybe a warehouse that had long walkways or aisles where you had to get your wireless signal down there for hand-held devices. You'd want something like this maybe at the end of that aisle that you could send the signal down the aisle as oppose to having the omni directional that we looked at earlier trying to cover that whole area and running into things like metal shelving and whatever you are stocking on those shelves and blocking that signal.

From the side, it's actually a thinner beam because these are more focused. It's wide but it's not as tall. It's definitely trying to get into a certain shape to cover a wider area but to be more focused to go a longer distance. As oppose to the omni that you chose in every direction, this is trying to go a little further. They tend to be stronger antennas.

How you mount them of course, when we say above, if you were to turn that antenna on its side, above would become the side. You can get a little creative with how those patterns are radiating and you need to be aware of that to ensure that you're getting the proper coverage. The same applies for omni directionals. Whether you mount them on the ceiling or on the wall, it will absolutely affect in which directions or how that radiating pattern is going to affect your environment.

Thank you for joining us today. Hopefully you learned a little something and maybe we can turn this guy into a smiley face. We'll see you next time.