Why You Shouldn’t Hang APs on the Wall Like a Clock

by | Nov 8, 2020 | Blog

There are some good reasons why your AP needs to hang on the ceiling, not the wall 

Wi-Fi is so resilient even when you don’t follow best practices it still works – BUT you are paying a price when you hang APs incorrectly. Let’s look at why. 

Transcripts

Don’t hang your APs on your wall like a clock. That’s not the way they go.

Welcome back to another little training video, and this will continue in the series of Wi-Fi design rules, “How to do better Wireless LAN Design”

And if you follow the rules, like any rule, it helps you. Now, there are times, of course, when you might have to break the rules, but for the most part, don’t put your APs on the wall like a clock.

You want to hang them down from the ceiling. That’s the way they’re designed.

Now, when I say that you’re like, “But, but, but why?” So let’s get in and see what happens in the “Why?” part.

On the screen, I have a copy of Ekahau. Ekahau is running, I have an Access Point placed in the middle of a football field.

I’m using a football field because you’ve been out on a big grassy place. This one happens to be an American football field. And about every 10 yards or every 10 meters, there’s a line. So you get an idea.

This access point is sitting in the middle of the field and covers 60, 70 meters in every direction. It has an omni antenna.

Let’s zoom in a bit and look at that omni antenna Let’s switch over here and I’m going to change to 2.4gHz. So we can see the 2.4 radio come over and zoom in a little bit and see the actual radio itself.

Here on the right is – it’s a Zonflex R710 2.4gHz. I’m setting it at 8dBm is the power level. And this is what it’s antenna pattern looks like.

Azimuth or the horizontal view or elevation and elevation is, if you think of elevation on a house, it’s the front view.

This is the vertical view or the side view of the Access Point. So when you place it on the ceiling, pointing down, there’s a little picture here, you can see a little picture of the AP pointing down, or zero degrees offset.

Well, this is the way this access point was designed to be installed.

Now, they do have other access points, specifically ones that have like four ethernet ports on them. Maybe a VLAN, made for hospitality.

They stick them on the wall like in a little gang box. Those are specifically made to be hung in that direction.

This access point, like most access points, has been designed to be mounted on the ceiling, pointing down – dome down.

If you make the mistake and, a lot of people do, I see it on a lot of forums where people think they did something, and taught you something right, because they really didn’t understand. And yet, because Wi-Fi is so incredibly resilient, when you do it wrong and you break the rules, Wi-Fi still works.

So, people don’t get punished for making mistakes and they go propagate.

Let me show you the actual thing that happens. And there’s two really important things that happen when you place an access point on the wall, kind of hang it like a clock.

If I hang this one on the wall like a clock, it’s like taking this and moving it up to 90 degrees. Now, when I let go here, you’re going to see the same effect happen as soon as I let go on the screen.

Now, come back up here and say for this access point, I changed the 2.4 and now this is a result, it happens to be pointing up, so I’m going to move it to the side just so it’s a little more obvious.

I’m going to grab the antenna, move it over and there you see the results. It still has coverage, about half the coverage it had before. So it’s just not going back the other way by rotating it and tilting it the way it was NOT supposed to go. We took the signal pattern and we pushed it another direction. It’s not going the direction we want it to go.

Oh, that’s sad.

Yeah. That’s what happens when you put on the wall. It changes the directionality of where the AP was covering, It’s no longer an omni.

Well, actually, it’s an omni it’s just rotated up vertically and it’s covering upstairs and downstairs rather than the floor that we’re on.

So, one of the reasons not to put an AP on the wall like a clock is its antenna pattern was not designed for that place and you will get other signal.

If we come here behind it. Oh, we’re still getting a signal. It just happens to be a -79

So the people on one side of the AP have even worse than they had before.

The other side still works.

But the other part of this is access points are designed with antennas that have polarization. In this case, it was vertically polarized. Meaning the signal was going up and down as it left the access point, when it was oriented in its original form. So the signals were going this way.

Now that we rotated it 90 degrees to the side, now the signals are now horizontal.

The receivers in this case will receive about six dB less signal because of the cross polarization.

So not only do:

1) – they cover an area that you thought was covered in and it’s not – you can see over here, it’s got this big hole.

2) the receivers who are still in the coverage zone are going to have a lower signal.

We’re not taking and Ekahau isn’t taking into effect right now the 6dB lower signal. If I just force that on here, I can say, “yeah, really, what’s going to happen – I needed to show 6dB higher”.

And that’s what the pattern would end up looking like for those people.

Again, like all rules, when you break it, Wi-Fi still works. It’s just if you want to do it correctly and you want to be efficient, how about if we just do things the way they were designed to go?

Let’s see if I can get back to zero.

And then we have the coverage that we always wanted.

If you have any further questions, come up to www.wirelesslanprofessionals.com. We have lots of resources for you to to learn from and to share.

Thanks for being part of the community.