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219 posts

Master Geek
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  Reply # 1646052 5-Oct-2016 17:20
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Jase2985:

 

like i keep saying ive tried channel 11 (11 + 7), it doesnt like it, ive tried channel 12 (12 + 8) it doesn't like it, ive tried channel 10 (10 + 6) it doesnt like it, ive tried channel 9 (9 +5) it doesnt like it, and i tried channel 8 (8+12) and it worked fine. when i put it on channel 7 it defaults to 7+3 and i cant force it to us the upper channel) i would love to use a center channel of 11 it just wont let me, hence the thread hence me asking. it seems like there is a bug or something thats stopping it doing it.

 

 

This is the problem with letting unqualified people work with wireless equipment.  A few points:

 

  • When you transmit a 20 MHz wide channel it affects the centre channel plus two channel below and above the centre channel.
  • Only 20 MHz channels 1, 6 and 11 are non-overlapping in the 2.4 GHz public spectrum
  • Co-channel interference (two radios with the same centre channel) is bad
  • Adjacent channel interference (two radios with different centre channels but overlapping - 1 & 5 for example) is worse

So you want 6+11 not 7+11.

 

Your only options are:

 

  • 20 MHz - 1, 6 or 11
  • 40 MHz - 1+6 or 6+11

Jase2985:

 

i have one access point that i can see that has an RSSI of greater than -82dB, the rest are closer to 90. that is on channel 5 and it has has no impact on the AP set on 1+5 so i cant see how it can affect the one on 11+7 when its closer to the other radio.

 

 

A 20 MHz neighbour on centre channel 5 (3, 4, 5, 6 and 7) can adversely affect a 40 MHz radio configured for centre channels 1+5 (1, 2, 3, 3, 4, 5, 6, 7).  The bolded channel (3) is in both 20 MHz wide channels - BAD.

 

The 11+7 (centre channels) 40 MHz wide channel affects 5, 6, 7, 8, 9, 9, 10, 11, 12, 13 so, again, it can be affected by a 20 MHz neighbour on channel centre channel 5 (3, 4, 5, 6 and 7).  The bolded channel (9) is in both 20 MHz wide channels - BAD.

 

 




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  Reply # 1646109 5-Oct-2016 19:47
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@crowdie while i may be unqualified that doesn't mean i don't know how the channels work, and while you may be qualified that also doesn't mean you know what you are talking about. so i dont know if you are using that as an insult or not but its not appreciated especially given the information you are trying to correct me on this is incorrect.

 

you can not choose 6+11 because it doesn't exist, look at the 2009 revision of the 802.11n standard. it clearly states primary channel is 7, secondary channel is 11 and covers channels 5 - 13.

 

https://en.wikipedia.org/wiki/IEEE_802.11n-2009

 

the 2 non overlapping 40mhz channels are 1+5 and 9 + 13, PERIOD

 

If i walk around my section to the furtherest reaches i can pickup 4 (2 are mine) 40mhz wifi networks, that are as follows in the 3 different wifi managment software programes i have here.

 

2 are on 1+5, 1 is on 8+12 and the last is on 11+7. there are 3 different manufactures devices there so your telling me based on the info you are trying to provide that all three of those manufactures are wrong?

 

and again you are missing the point, its not working on a few channels for what ever reason but its working on others even though its overlapping with the same channels. there is no discernible reason why its not working other than a software bug.


 
 
 
 


219 posts

Master Geek
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  Reply # 1646118 5-Oct-2016 20:14
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Jase2985:

 

 

 

the 2 non overlapping 40 MHz channels are 1+5 and 9 + 13, PERIOD

 

 

Are you using the channel block codes or the ETSI channels?

 

If you use inSSIDer (Windows) or WiFi Analyzer (Android) what do you see?

 

The following is from Chapter 18 "802.11n" of the official CWNA Study Guide:

 

"Deploying 40 MHz HT channels at 2.4 GHz unfortunately does not scale well in multiple channel architecture.... although fourteen channels are available at 2.4 GHz, there are only three non-overlapping 20 MHz channels available.... When the smaller channels are bonded together to form 40 MHz channels in the 2.4 GHz ISM band, any two 40 MHz channels will overlap... In other words, only one 40 MHz channel can be used at 2.4 GHz"

 

 

 

 




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  Reply # 1646127 5-Oct-2016 20:36
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for 20mhz yes, but not for 40Mhz its 1+5 and 9+13 (centre channels being 3 and 11).

 

given we allow the use of channel 12 and 13 in NZ that differers to the FCC and US regs for 802.11n. We have our own standards managed by the RSM and they allow the use of those 2 channels.




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  Reply # 1646140 5-Oct-2016 20:45
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ive also told you what i see but you dont seem to be reading what i type

 

if i walk around my section to the furtherest reaches i can pickup 4 (2 are mine) 40mhz wifi networks, that are as follows in the 3 different wifi management software programs i have here.

 

 2 are on 1+5, 1 is on 8+12 and the last is on 11+7. there are 3 different manufactures devices there so your telling me based on the info you are trying to provide that all three of those manufactures are wrong?

 

none have the spacing you mention

 

just for you an image, as you can see there are 2 40mhz networks there, both are mine. 1+5 and 9+13 notice the minimal to zero overlap on channel 7?

 

Click to see full size


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