How to tell a wlan card supports RFMON mode

Solution 1:

RFMON support depends on the chipset used in the adapter. Research the wlan card, find out what chipset it uses, and then find out if the chipset can operate in RFMON mode with the right driver.

This website is an excellent resource for just that.

Solution 2:

To check if your wireless card supports monitor mode, you can use iw list.

Run in a terminal:

iw list

Output:

Supported interface modes:
     * IBSS
     * managed
     * AP
     * AP/VLAN
     * monitor

In Supported interface modes, if you find monitor to be present then that means that your wireless card supports monitor mode.