It is important to make sure your wifi card is supported in pfSense (go to https://www.netgate.com/docs/pfsense/wireless/supported-wireless-cards.html and click on "Wireless Card Support"). Even if you check that list, you can still end up with problems. I saw a weird issue a few months ago where a supported card did not work because of the country code reported by the card and an issue with how that particular BSD driver treated country codes. Wireless adapter support doesn't seem to be great in pfSense, and the tune-ability of the wireless connection isn't the best in the pfSense GUI. I've actually wondered if it wouldn't be better just to buy a nice wireless bridge and connect it to the pfSense box via ethernet.
