My AP operates in the 5Ghz band. There are no problems using Channel 36 to 64; however, clients can't even detect the SSID if I use Channel 100 to 140.

Below is a screenshot of Netspot showing all the signals in my area. It seems like its not my router issue, and that my clients can't detect anything else in the 100-140 channel range. Why is that? Is it a regional issue? I would like to have my router run on an orthogonal channel without any network interfering with it, hence I would like it to run on channel 100+.

netspot showing signals in my area

  • You know I have the same problem. The USB-N53 detected and ran fine with my machine when it was windows 7, but now with the upgrade, it only detects 2.4ghz channels, even though the settings in properties are set to 2.4/5.0 and even just 5.0 - just can't seem to do it. It must be something to do with a new configuration of windows, or the drivers not being properly formatted for Win 8 or Win 10. I am going to try to install win 7 drivers and see if that helps. All the wiki info about channels, has nothing to do with the problem. My device saw channel 157 under Win 7, and is no longer seeing ch
    – user13560
    Jan 26, 2015 at 2:36

2 Answers 2


802.11a Frequency Channel Map

Perhaps this will help. Also, consult Wikipedia for futher reference. In short, in the US, the H band is restricted due to interference issues with Terminal Doppler Weather Radar (TDWR). (at least for outdoor use.)

  • 1
    This is an old representation of the channel allocations, at the very least with regards to the FCC (I can't speak authoritatively to non-FCC regions). The DFS channels 100-140 were added in 2007.
    – YLearn
    Oct 29, 2014 at 18:30
  • And there was an advisory in Sept. 23, 2014. (follow the wiki footnote #19)
    – Ricky
    Oct 29, 2014 at 19:12
  • This is a recent interim ruling and only removed three of the channels from use for now. The others are still available for use (with restrictions to enforce they actually follow DFS properly).
    – YLearn
    Oct 29, 2014 at 19:28
  • If his AP and/or driver(s) are old enough, they may not allow the H band channels. Checking the Cisco 1242 here, running 4 year old software, it allows those channels, but has 120-128 disabled because it sees the TDWR from RDU (17km away)
    – Ricky
    Oct 29, 2014 at 19:40
  • Obviously, if you are running code that predates modern regulations, it won't be accurate, but that cuts both ways and part of why one should keep their wireless up to date. But this also brings up the other issue I have with this table, which is the only H band I know doesn't cover the frequencies in question (NATO H band was 6-8GHz or thereabout?). Outside of the radar band designations, and from the FCC perspective, they are UNII-2C or more commonly referred to as UNII-2-Extended in the 802.11 world.
    – YLearn
    Oct 29, 2014 at 21:22

Radio frequency is a limited resource that is managed individually by various organizations geographically. In the US, the government entity that regulates the use of RF is the FCC. As of February 2013, the FCC did agree to additional frequency for unlicensed use and the current allocation is as follows (I apologize as I forget from where I saved this image and when searching came across it in several locations so can't attribute properly): enter image description here

There are several challenges to overcome when using the newly available frequencies, but we may see their adoption in some products as early as 2015.

Other countries/regions will allow/disallow frequency based on their own requirements and current (or historic) uses.

Since there are many differences globally in which frequencies can be used (and at which power levels), if you move from one region to another your device may try to use frequencies that may be illegal to use in that region.

To resolve this problem, 802.11d was approved in 2001. This added the ability to include a country/region code into the beacons, probe requests and probe responses of an 802.11 device.

AFAIK, all modern access points now include support for 802.11d. However the client support is typically dependent on the wireless driver and network implementation on the device.

For example, on one of my Linux systems, I can find this output relating to it adjusting channels/power levels based on 802.11d by using "dmesg" after connecting to a wireless network:

[  403.990529] cfg80211: Calling CRDA for country: US
[  403.993283] cfg80211: Regulatory domain changed to country: US
[  403.993286] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[  403.993287] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2700 mBm)
[  403.993288] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 1700 mBm)
[  403.993289] cfg80211:   (5250000 KHz - 5330000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[  403.993289] cfg80211:   (5490000 KHz - 5600000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[  403.993293] cfg80211:   (5650000 KHz - 5710000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[  403.993294] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 3000 mBm)
[  403.993295] cfg80211:   (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 4000 mBm)

I know OSX also supports 802.11d, but I don't have an OSX system to provide output or to say how to get this information exactly. Based on this blog post, it appears that unlike my Linux system (which appears to set the available channels each time it connects), OSX may set channels/power levels based on the first beacon if finds when the wireless network interface comes up. This can be problematic if you have devices advertising incorrect country/region codes in your area. I haven't tested this myself, so can't speak to the accuracy of the blog post.

So, going back to my FCC channel example above, even once the technical challenges of the new channels are overcome and they are supported on new access points, if you client doesn't recognize them as part of the "US" region, they won't be available when 802.11d kicks in.

To specifically answer your question, we would need to know a bit more information. Your guess that it may be based on your region is close, however it is actually based on the region your client thinks it is in. If it thinks it is in a region where channels 100-140 are not usable, you won't be able to use them (whether or not you really could be using them is another matter entirely).

Conversely, you need to make sure your access point is configured for the correct region. If it isn't, it is possible that you could be subject to legal repercussions if you are reported or found to be using frequencies that you don't have the right to use.

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