Wireless Access


Antenna channel support only lower channels on 5ghz band

Hello everyone

These days i realized of something interesting which i want to share.

I ll start with the history first:


We have a client which has a bunch off bgn laptops, and they needed to start  using them in a really high interference area for 2.4ghz  band.


They didnt have any wifi in that area so in the initial site survey we notice that in that area there was too much noise and interference in 2.4ghz and we didnt recommend them using 2.4ghz at all... We even show them and plugged an ap and put it on just 2.4ghz and he was able to see that it was useless... too many packet lost.

So we told them that they need to buy new laptops with 5ghz support or at least usb dongles that support 5ghz.

They decided for the cheaper choice which was buying like 20  of those usb dongles, they also had a few laptops which had abgn 2x2


I configured everything and i did just turn on the 5ghz band on all the APS, as 2.4ghz is useless...  i put it on air monitor that band.


The thing is that we start the test and everything seems to be  working good.

Here comes the interesting part.

A few days ago the client reported me that there were some devices that even if they were in front of the client  they had low signal, and he even could disconnect and reconnect to force the roaming but that didnt work.   

I went in there to see what was happing and i was looking that the laptop with the dongle were just connect to a certain AP...   I notice that the AP was on channel 36 and the AP in front of it was on channel 157.   Just as test we turned that AP on  channel 36 off so it was forced to connect to the AP on channel 157.    The dongle was able to see the AP but he was not able to connect... it stay in there authenticating... 

So what i did next was turning off those channels.. i mean the channels in the upper band...and just leave the channels in the lower band, and there we go, it connected, we ran more test and everythings works correctly.


Now that make me think wth??


I though that at least all the dongles and integrated antenas did support at least lower and upper channels on 5ghz band.   Now i just got notice thats not true... those dongles just support lower band and thats it, which means they just support 4 channel out of 23 channels on 5ghz band... well thats a bummer...

I was aware that some devices might not support DFS channels but i was not aware that some devices woudl just support lower channels(36,40,44,48)


Now this make me thing back the times when i though why isnt the band steering working or why isnt clientmatch changing it to 5ghz band when its soo obvious  that it should be on 5ghz(looking that there is soo much interference on 2.4ghz and there is none on 5ghz).  Now it all make sense(not saying that in all the times it would be this.. but it could be sometimes)


Now i wonder if this information appear in the documentation of the integrated antena? at least it does not appear on the dongles datasheet.. they just advertise that it support 5ghz but not which channels support  *sigh*


Once again this make me think how lilttle i know about wifi :) 







Product Manager - Aruba Networks
Alternetworks Corp

Re: Antenna channel support only lower channels on 5ghz band

First, those are terrible 802.11ac client adaptors. Most of them , They only support 2 spatial streams, which means they could only do the 867Mbps flavor of 802.11ac instead of the 1300Mbps flavor, and also, when doing 802.11n, they can only do the 300Mbps flavor instead of the 450Mbps flavor. And finally, they're only USB 2.0, which means they're limited to USB 2.0's 480Mbps (or less) bus speed.


 36,  40,  44,  48  
 52,  56,  60,  64 (DFS)  
100, 104, 108, 112 (DFS)  
116, 120, 124, 128 (DFS) Generally not allowed in North America due to possible interference with Terminal Doppler Weather Radar systems near some airports.  
132, 136, 140, 144 (DFS) Only works if your AP and clients support the recently-added channel 144  
149, 153, 157, 161


read here:



and then check the chipset if it supporting your needs (hight channels on ghz)


Here is an example from AC6200 (AC1200) of Edimax doc:

(always read)

26-09-2014 08-50-31.jpg



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