AirPort Express has 40Mhz Channel Width "Disabled"

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Level 1

4 points

AirPort Express has 40Mhz Channel Width "Disabled"

Dear Community,

We were trying to optimise our AirPort Network (using extended wireless) and used a product called WiFi Scanner to investigate.

It has detected that one of our AirPort Express units is running at 5GHz but will only operate on the 20Mhz Channel Width. When we look at the details, it says that 40Mhz is disabled.

All devices have been Factory Reset, running the same most up to date version (7.6.4) but no matter what we try the 40Mhz channel is disabled and will not be enabled.

Does anyone have any idea why this might be the case for one AirPort Express unit?

Thanks in advance.

Bradley Porter

Posted on Aug 31, 2015 9:28 AM

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Answer 1

Aug 31, 2015 10:19 AM in response to BRJP

What model of AirPort Express do you have? Does it look like this, perhaps?

Or, does it look like this?

Is the AirPort Express connecting wirelessly to the main Apple router.....or....does the AirPort Express connect to the main AirPort using a permanent, wired Ethernet cable connection?

What version of AirPort Utility are you using to set up and configure the AirPorts?

Does anyone have any idea why this might be the case for one AirPort Express unit?

We don't have the info that we need yet, but a guess would be that you have configured the AirPort Express to wirelessly extend the network, and although the Express might be producing a 5 GHz signal, it is actually connecting to the main Apple router at the 2.4 GHz frequency. If that is the case, then the Express is not receiving a Wide Channel signal....so it will not extend one.

Less likely...but possible....is that the Express was previously configured using an older version of AirPort Utility which did have a setting to enable or disable Wide Channels, and the settings have been lost or corrupted.

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Answer 2

BRJP Author

Level 1

4 points

Aug 31, 2015 11:27 AM in response to Bob Timmons

Hi Bob,

Thank you for offering to help - much appreciated.

We have 1 AirPort Extreme as the base station and 3 AirPort Expresses connecting to Extended the Network, All (according to WiFi Scanner) connect at 5GHz and 40Mhz apart from one as outlined below.

In answer to some of your questions and comments please see below:

Bob Timmons wrote:

What model of AirPort Express do you have?

Its the one with the two ethernet ports.

Bob Timmons wrote:

Is the AirPort Express connecting wirelessly to the main Apple router.....or....does the AirPort Express connect to the main AirPort using a permanent, wired Ethernet cable connection?

Yes - its connecting to an AirPort Extreme wirelessly. This was performed by factory defaulting the Express and then using the AirPort Utility to 'extend a network' once it was detected.

Bob Timmons wrote:

What version of AirPort Utility are you using to set up and configure the AirPorts?

6.3.5 (635.2) is the AirPort Utility version. All versions of AirPorts are 7.6.4.

Bob Timmons wrote:

We don't have the info that we need yet, but a guess would be that you have configured the AirPort Express to wirelessly extend the network, and although the Express might be producing a 5 GHz signal, it is actually connecting to the main Apple router at the 2.4 GHz frequency. If that is the case, then the Express is not receiving a Wide Channel signal....so it will not extend one.

This feels like the right path to me - however, the other devices are all connecting at 5GHz and 40Mhz which is a little confusing. When we look at the tool (WiFi Scanner) its says that "40Mhz SGI: Disabled". Therefore max through-put is 144Mbps.

Bob Timmons wrote:

Less likely...but possible....is that the Express was previously configured using an older version of AirPort Utility which did have a setting to enable or disable Wide Channels, and the settings have been lost or corrupted.

Would this have been resolved by Factory Default reset were performed?

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Answer 3

Aug 31, 2015 11:49 AM in response to BRJP

What happens if you temporarily power off the other two AirPort Express devices? Will the Express connect correctly now.....if you test it temporarily with a line-of-sight setup between the Express and the main router?

If not, then everything that you are telling us indicates that you have a defective AirPort Express.

I ran a few quick checks here on a spare Express using a wireless connection.....and even with the Express a few rooms away from the main router......it provides a 40 MHz wide channel signal. Click on the image below to enlarge to show more details.

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Answer 4

BRJP Author

Level 1

4 points

Aug 31, 2015 1:34 PM in response to Bob Timmons

Bob Timmons wrote:

What happens if you temporarily power off the other two AirPort Express devices? Will the Express connect correctly now.....if you test it temporarily with a line-of-sight setup between the Express and the main router?

Thanks Bob - it seems that if I bring the router really close to the main router, it will connect at 40Mhz. Maybe it is some material in the way but we are not talking rooms away, we are talking the next room and the device is struggling.

I guess the signal is just getting blocked?

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Answer 5

Aug 31, 2015 2:10 PM in response to BRJP

What happens if you swap Expresses and test that way? Does the other Express perform better or about the same?

If you are using the paid version of WiFi Scanner, it has a nice feature to measure Signal to Noise, or SNR of a wireless signal. That is the acid test as far as connection quality. You want to see an SNR of at least 30 dB....more would be better.....when you check the signal that the Express receives from the main router.

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Answer 6

BRJP Author

Level 1

4 points

Aug 31, 2015 2:39 PM in response to Bob Timmons

Well Bob, before I even moved another AirPort, I moved my MacBook Pro around and had a look at the stats produced by Wi Fi Scanner. I think I can see why my router was not connecting properly.

Sitting in the next room (in the position where I had the Airport when it would not connect at 40Mhz) I captured the attached. The highlighted line shows 18 SNR which is well below the 30. I am pretty close - 5 meters between laptop and base station but the SNR drop off is considerable. This must be why I was having issues.

My next issue is trying to work out why the signal deteriorates so much in such a short space and distance. Maybe this is the house construct or maybe I have high noise? I am not sure but would the signal really drop off so substantively in that short space?

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Answer 7

Aug 31, 2015 3:00 PM in response to BRJP

Your guess is as good as mine. Wireless has always been half science and half voodoo.

Some wall insulation material....with a metal foil backing on one or both sides of the material.....will block a good deal of the wireless signal. If you have a mirror on the wall, remember that it is mostly sheet metal, so not much signal will get through.

Wireless travels in a straight line between the main router and receiving device, so any obstruction in the direct signal path can have a big effect.

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