Maintained by: @morrownr
Updated on: 2026-07-06
Note: If you find that any of the answers below no longer work or are in need of an update, please let me know by posting a message in issues. Keeping the information on this site current is a challenge and can only work with your help. Thanks.
Question 1 - It appears that the Wireless Regulatory information is not correct in my system. How can I fix this?
Question 2 - My 6 GHz band shows as disabled when I run iw list. I want to be able to use the 6 GHz band. How can I fix this?
Question 3 - Why do I see high levels of jitter with my mt7921 or mt7922 based wifi cards (PCIe or M.2)?
Question 4 - Why do I see high levels of jitter with my mt7921 or mt7925 based USB WiFi adapters?
Question 5 - I am having problems with my Alfa AXML or Alfa AXM. The wifi is not working. It seems to crash when coming up. What can I do?
Question 6 - I live in the US and am trying to use a tri-band USB WiFi adapter as an AP with band 4 (6 GHz). How do I make it work?
Question 7 -No. 7 - Question: My USB WiFi adapter is showing up as a CDROM or Flash drive instead of a WiFi adapter. What is the problem?
Question 8 - When my computer comes back to life from sleep mode, my USB WiFi adapter does not wake up without a reboot. How do I fix this?
Question 9 - Can the C-states setting in the bios cause problems with Linux wireless drivers?
It appears that the Wireless Regulatory information is not correct in my system. How can I fix this?
Medern wireless routers and APs advertise the country to clients using an IEEE 802.11d Country Information Element (IE) within its regular wireless Beacon and Probe Response frames. This allows the Linux kernel to automatically set the appropriate country information in your client system. If the country information is not being set correctly in your modern Linux system, it could be that your wireless router or AP is too old to have the capability to provide this information or it could be that the settings are not properly set in your wireless router or AP.
If you are using hostapd to build your own access point, you need a specific setting to enable the capability:
You should set the regulatory domain in your hostapd.conf file using two lines:
country_code=US (Sets the regulatory domain, e.g., 'US' for the United States)
ieee80211d=1 (Enables 802.11d so the AP actively broadcasts the country code to clients)
If it appears that the wireless router or AP is not the problem, further troubleshooting is in order:
Know the Country Code for your Country: List of Current ISO 3166 country codes ( Example: Panama = PA )
For reference: Official Linux Wireless documentation: Linux Wireless documentation
Information: When you run iw reg get you should be able to see the country code setting of your system and the information about the bands that you can use. Here is an example of what you should see. My country is US, so I see the following:
$ iw reg get
global
country US: DFS-FCC
(902 - 904 @ 2), (N/A, 30), (N/A)
(904 - 920 @ 16), (N/A, 30), (N/A)
(920 - 928 @ 8), (N/A, 30), (N/A)
(2400 - 2472 @ 40), (N/A, 30), (N/A)
(5150 - 5250 @ 80), (N/A, 23), (N/A), AUTO-BW
(5250 - 5350 @ 80), (N/A, 24), (0 ms), DFS, AUTO-BW
(5470 - 5730 @ 160), (N/A, 24), (0 ms), DFS
(5730 - 5850 @ 80), (N/A, 30), (N/A), AUTO-BW
(5850 - 5895 @ 40), (N/A, 27), (N/A), NO-OUTDOOR, AUTO-BW, PASSIVE-SCAN
(5925 - 7125 @ 320), (N/A, 12), (N/A), NO-OUTDOOR, PASSIVE-SCAN
(57240 - 71000 @ 2160), (N/A, 40), (N/A)
Note: If you are located in another country, the 2 letter country code should reflect your country code.
Example of what you may see if there is no country code set and your system is having to use the global defaults:
$ sudo iw reg get
global
country 00: DFS-UNSET
(2402 - 2472 @ 40), (6, 20), (N/A)
(2457 - 2482 @ 20), (6, 20), (N/A), AUTO-BW, PASSIVE-SCAN
(2474 - 2494 @ 20), (6, 20), (N/A), NO-OFDM, PASSIVE-SCAN
(5170 - 5250 @ 80), (6, 20), (N/A), AUTO-BW, PASSIVE-SCAN
(5250 - 5330 @ 80), (6, 20), (0 ms), DFS, AUTO-BW, PASSIVE-SCAN
(5490 - 5730 @ 160), (6, 20), (0 ms), DFS, PASSIVE-SCAN
(5735 - 5835 @ 80), (6, 20), (N/A), PASSIVE-SCAN
(57240 - 63720 @ 2160), (N/A, 0), (N/A)
Notice that country 00: DFS-UNSET indicates no country code is set.
What are some of the results of the country code not being set?
- 5 GHz channels do not allow access point operation (i.e.
iw listshows No-IR on all channels). - Some 5 GHz channels that should be available are not available.
- 6 GHz channels completely disabled.
- 2.4 GHz channel may show a lower txpower than what is allowed in your country.
The list above is only a partial list of problems that can arise if the country code is not set properly.
The first step to fix this problem is to try to set the Country Code manually:
Open a Terminal interface - Ctrl + Alt + T
sudo iw reg set AU
Check to see if this fixes the problem:
iw reg get
If the Country Code is now set, I recommend that you skip to Answer 2 below to make the setting persistent. If the Country Code is not set, then I recommend trying Answer 1.
Answer 1:
If you are using Arch Linux or distros that are based on Arch Linux first follow the following section, otherwise skip it:
Setting the Wireless Regulatory Domain in Arch Linux
Install wireless-regdb:
If you haven't already, install the wireless-regdb package: sudo pacman -S wireless-regdb
Edit /etc/conf.d/wireless-regdom
Open the file with a text editor and uncomment the line containing your desired regulatory domain. For example, to set it to the United States, you might uncomment REGDOMAIN="US".
Save the file
Reboot:
sudo reboot
To check if the country code setting of your system is now correct:
iw reg get
If you are NOT using Arch Linux or distros that are based on Arch Linux
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/cfg80211.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options cfg80211 ieee80211_regdom=AU
Note: If your country code is not AU, you will need to replace AU with your country code
Save the file: (if using nano)
Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
To check if the country code setting of your system is now correct:
iw reg get
Answer 2:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/systemd/system/regdom.service
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following lines to the file:
[Unit]
Description=Set wireless regulatory domain to US
[Service]
ExecStart=/usr/sbin/iw reg set US
[Install]
WantedBy=multi-user.target
Note: If your country code is not US, you will need to replace US with your country code
Save the file: (if using nano)
Ctrl + O, Enter, Ctrl + X
Run the following command to activate the new service file:
sudo systemctl enable regdom.service
Reboot:
sudo reboot
After reboot it should have run the command. You can check with:
systemctl status regdom
To check if the country code setting of your system is now correct:
iw reg get
My 6 GHz band shows as disabled when I run iw list. I want to be able to use the 6 GHz band. How can I fix this?
Answer: This may happen with MEDIATEK cards and adapters on Linux 6.7.x or newer. There has been a lot of work on the WiFi support in Linux over the last year. We have seen an uptick in WiFi problems as a result. As of kernel 6.12, things seem to be getting better but there is work to be done.
A new feature called "CLC (Country Location Control)" must be disabled in the
mt7921_common module in order to use the 6 GHz band (for now). Make a file
called /etc/modprobe.d/mt7921.conf containing options mt7921_common disable_clc=1.
Example:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/mt7921.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options mt7921_common disable_clc=1
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Information: https://bugzilla.kernel.org/show_bug.cgi?id=218731
Alternate solution: https://www.michaelstinkerings.org/the-mt7922-6ghz-debacle-why-linux-users-cant-use-wifi-6e-and-how-i-fixed-it/
Note: A weak signal or high congestion can cause high levels of jitter. The below answers do not currently address these situations.
Information: Variance in ping times is called "jitter" in networking terminology; it refers to the inconsistency in the arrival time of data packets, essentially measuring how much your ping fluctuates over time. Jitter disrupts the smooth flow of data, resulting in noticeable disruptions, particularly in time-sensitive activities.
Information: All 3 chips use the mt7921e driver.
Answer: You can try disabling power management for the card as follows:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/mt7921.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options mt7921e disable_aspm=Y
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Note: A weak signal or high congestion can cause high levels of jitter. The below answers do not currently address these situations.
Information: Variance in ping times is called "jitter" in networking terminology; it refers to the inconsistency in the arrival time of data packets, essentially measuring how much your ping fluctuates over time. Jitter disrupts the smooth flow of data, resulting in noticeable disruptions, particularly in time-sensitive activities.
Important: Jitter can often be caused by or increased greatly by low signal level so I always check signal level before trying anything else. A signal level greater than -52 dBm may be at a level that can adversely affect jitter levels. Examples of signal levels greater than-52 dBm would be -53 dBm, -54 dBm, -55 dBm, etc. You may need to take action to lower the signal level reading (that is, increase the signal strength). Placement of the wireless devices can often contribute to poor signal strength. If you have investigated signal strength and are still seeing less than optimal results, see below.
Answer 1: First test to see if power_save is causing the issue:
Open a Terminal interface: Ctrl + Alt + T
Run the following command (remember to change wlan0 to the name of your wireless interface):
iw wlan0 set power_save off
Do not reboot as that will return power_save to on.
Test your system to see if there is improvement. If there is improvement, you may want to check the additional answers below for a persistent solution.
Answer 2: If your system uses Network Manager, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
sudo nano /etc/NetworkManager/conf.d/wifi-power_save.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following lines to the file:
# Values are 0 (use default), 1 (ignore/don't touch), 2 (disable) or 3 (enable).
wifi.powersave = 2
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Answer 3:
If your system uses systemd, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
Note: You can use your own favorite text editor in place of nano if you wish.
sudo nano /lib/systemd/system/wifi-power_save.service
Add the following lines to the file (remember to change wlan0 to the name of your wireless interface):
[Unit]
Description=Disable power_save for specific USB WiFi adapter
After=network.target
[Service]
Type=oneshot
ExecStart=/usr/bin/iw wlan0 set power_save off
[Install]
WantedBy=default.target
Save the file: Ctrl + O, Enter, Ctrl + X
Run the following command to enable the new service:
sudo systemctl enable wifi-power_save.service
Run the following command to verify that the service is functioning properly after rebooting:
Note: remember to change wlan0 to the name of your wireless interface.
iw wlan0 get power_save
Run the following command to disable the service if you need to disable it:
sudo systemctl disable wifi-power_save.service
I am having problems with my Alfa AXML or Alfa AXM. The wifi is not working. It seems to crash when coming up. What can I do?
Update as of the release of Ubuntu 25.04: Both adapters are working fine with the 25.04 release of Ubuntu which uses kernel 6.14 and the most up to date firmware files. WiFi and Bluetooth both work. It was a bluetooth related bug that was preventing wifi from working.
Answer: This was a known problem that started in 2024 after the release of kernel 6.7. There were unsuccessful attempts to fix this problem but a fix was finally found in late 2024 and worked it way into kernel 6.14. It was a strange problem in that bluetooth was involved. Most adapters with the mt7921au chipset do not have this problem because bluetooth is not active. The adapters listed in the question are the only ones known to have bluetooth active so this problem only showed up on the Alfa AXML and AXM. If you are using a kernel that has not been patched, a workaround is to disable bluetooth. The simplest way to disable the bluetooth support for these adapters is to delete the firmware file for bluetooth support for the mt7921au chip:
sudo rm /lib/firmware/mediatek/BT_RAM_CODE_MT7961_1_2_hdr.bin
You may also want to ensure you are running the latest firmware files for the mt7921au chipset
Make sure you're running the latest WiFi firmware:
As of 2025/05/06, the most up to date firmware files:
[18615.766176] mt7921u 1-9.3:1.3: WM Firmware Version: ____010000, Build Time: 20241106151045
Instructions for updating the firmware can be found at the following location:
If WiFi is not working in a USB3 port, try a USB2 port or a USB2 hub.
The above solution, that shuts down bluetooth support, may not work well for people that have other bluetooth support in their system and they want to use it. In that case, simply delete BT firmware file for your adapter.
I live in the US and am trying to use a tri-band USB WiFi adapter as an AP with band 4 (6 GHz). How do I make it work?
Answer: This capability works in many locations in the world such as the EU countries. It is currently problematic in the US due to US wireless regulations. This is true of USB WiFi adapters with Mediatek and Realtek chips as the issue is not with the hardware or drivers. The problem is with US wireless regulations as shown in db.txt (I'll add more information on how to research this as I have time.) Here is a link that explains the problem:
https://patchwork.kernel.org/project/linux-wireless/patch/000201db8822$98f28da0$cad7a8e0$@gmail.com/
My USB WiFi adapter is showing up as a CDROM or flash drive instead of a WiFi adapter. What is the problem?
Answer: Your USB WiFi adapter showing up as a CDROM or flash drive (often with ID 0bda:1a2b) instead of functioning as a network adapter (such as ID 35bc:0102 or similar) is likely due to a "mode-switching" issue. Some USB WiFi adapters include onboard storage that contains a driver for Windows. When plugged into a system for the first time, they initially present themselves as a virtual CD-ROM or flash drive containing a driver. This is fairly common with USB WiFi adapters that use Realtek chipsets.
In Linux, the usb_modeswitch utility generally handles this issue but there are situations where it does not work as expected.
Your options:
Option 1: Send your adapter back and get one that is single-state (no storage onboard). If that is not possible then:
Option 2: You need to check if the VID/PID for your adapter is in the usb_modeswitch data file. See the following link for more information:
https://github.com/morrownr/USB-WiFi/blob/main/home/How_to_Modeswitch.md
Option 3: If you have exhausted recommendations from the information in item 2, then:
You may be able to make the adapter work in wifi mode with the following method:
How to add kernel parameters with GRUB in Ubuntu:
Note: This method may vary by distro so if you are not using Ubuntu, please consult the documentation for your distro.
Once your device has booted, use a text editor to open the following file:
$ sudo nano /etc/default/grub
Add parameters to GRUB_CMDLINE_LINUX while keeping the following in mind:
Enter parameters inside the double-quotes
Leave a space before each new parameter
Don’t add space round = and other punctuations for each key-value
Don’t add line breaks
If your original line looks like:
GRUB_CMDLINE_LINUX="quiet"
Then your updated line should read like:
GRUB_CMDLINE_LINUX="quiet usb-storage.quirks=0bda:1a2b:i"
Note: If the storage VID/PID (ID) is not 0bda:1a2b, you will need to change 0bda:1a2b to the storage mode VID/PID of your adapter.
Save and close the editor.
Update GRUB with its new configuration:
$ sudo update-grub
$ sudo reboot
Note: If your distro does not use grub, the RasPiOS is an example, you will need to read your distro docs to see how to do the above.
Example for Raspberry Pi OS:
$ sudo nano /boot/firmware/cmdline.txt
add the following to the end of the console= line:
usb-storage.quirks=0bda:1a2b:i
Save, close the editor and reboot.
When my computer comes back to life from sleep mode, my USB WiFi adapter does not wake up without a reboot. How do I fix this?
Information: While this is not a common problem, it does happen and it can be a challenge to discover the exact cause in each system as the problem may be a BIOS error or a problem in various drivers. However, this problem can usually be worked around by turning power save off for your adapter. The extra power used is marginal.
Answer 1: First test to see if power_save is causing the issue:
Open a Terminal interface: Ctrl + Alt + T
Run the following command (remember to change wlan0 to the name of your wireless interface):
iw wlan0 set power_save off
Do not reboot as that will return power_save to on.
Test your system to see if there is improvement. Let the system go to slepp and then bring it back. If there is improvement, you may want to check the additional answers below for a persistent solution.
Answer 2: If your system uses Network Manager, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
sudo nano /etc/NetworkManager/conf.d/wifi-power_save.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following lines to the file:
# Values are 0 (use default), 1 (ignore/don't touch), 2 (disable) or 3 (enable).
wifi.powersave = 2
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Answer 3:
If your system uses systemd, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
Note: You can use your own favorite text editor in place of nano if you wish.
sudo nano /lib/systemd/system/wifi-power_save.service
Add the following lines to the file (remember to change wlan0 to the name of your wireless interface):
[Unit] Description=Disable power_save for specific USB WiFi adapter After=network.target
[Service] Type=oneshot ExecStart=/usr/bin/iw wlan0 set power_save off
[Install] WantedBy=default.target
Save the file: Ctrl + O, Enter, Ctrl + X
Run the following command to enable the new service:
sudo systemctl enable wifi-power_save.service
Run the following command to verify that the service is functioning properly after rebooting:
Note: remember to change wlan0 to the name of your wireless interface.
iw wlan0 get power_save
Run the following command to disable the service if you need to disable it:
sudo systemctl disable wifi-power_save.service
Yes. CPU C-states (power-saving sleep states) can cause latency and communication drops with USB and PCIe wireless devices. Deep sleep states shut down parts of the CPU, USB bus and PCIe bus. This can lead to wireless devices that occasionally fail to wake up in time, causing the connection to drop, the driver to hang or performance to suffer.
How C-States Cause USB Disconnects
When your CPU rapidly shifts into deep C-states (like C6 or C7) to save power, it briefly lowers the voltage and clock speeds to the motherboard's chipset. USB controllers and connected wireless adapters may fail to wake up in time from this power dip, resulting in dropped packets, sudden disconnections, or the device entirely dropping off the USB bus.
- The Power Management Conflict
Wireless drivers for Linux work closely with your system's pcie_aspm (Active State Power Management) and the CPU's C-States. If the CPU goes into a deep sleep state (like C6 or C10), the power supplied to the PCIe lane hosting your Wi-Fi card drops. When the network needs to send or receive data, the wake-up latency (latency in waking the CPU core and PCIe lane) can cause the Wi-Fi driver to time out or lose connection entirely.
- How to Diagnose
You can check if your system is aggressively putting the Wi-Fi adapter or card to sleep by disabling power management via the command line. Open your terminal and do the following:
Determine the name of your wireless interface by running ip link:
ip -br link
Turn off power saving by running the following (replacing wlan0 with your actual interface):
sudo iw dev wlan0 set power_save off
Disable PCIe Link State Power Management (ASPM):
If Wi-Fi drops only happen after periods of inactivity, your system might be powering down the adapter/card.
Edit your GRUB bootloader configuration:
sudo nano /etc/default/grub
Find the line that starts with GRUB_CMDLINE_LINUX_DEFAULT and add pcie_aspm=off to the existing quotes.
Save the file:
Ctrl + O, Enter, Ctrl + X
Update grub to apply the changes:
sudo update-grub
(or sudo grub2-mkconfig -o /boot/grub2/grub.cfg depending on your distro)
Reboot your system.
- Modifying C-State Settings
If OS-level power tweaking doesn't resolve the issue, you can loert the C-State setting in your BIOS.
Intel CPUs: Some Linux kernels employ the intel_idle driver, which occasionally ignores BIOS C-State limits. You can force the Linux kernel to limit C-States by editing your /etc/default/grub file and adding intel_idle.max_cstate=0 to GRUB_CMDLINE_LINUX_DEFAULT.
AMD CPUs: Some motherboards hide C-State power settings. If your Wi-Fi is unstable when idle, check your BIOS for a setting named "Power Supply Idle Control" and set it to "Typical Current Idle". This prevents the CPU from aggressively entering deep sleep modes like C6.