Unfortunately I have problems with a lot of WiFi adapters because of the many fuses inside of the π dropping voltages (starting with 4,5V from my Notebook/USB hub, it goes down to 3,8V on the USB connector). But adding a short wire bridging all those fuses helps ;-).
The dongle used is really old, it's a
Bus 001 Device 005: ID 07b8:b21d AboCom Systems Inc RT2573
and gets quite warm (correlates well with the high power consumption and hence voltage drop on the fuses), also looses contact with my (just nearby) access point frequently.
[ 2140.585617] ieee80211 phy0: wlan0: No probe response from AP 68:7f:74:5e:42:ff after 500ms, disconnecting.
[ 2140.607093] cfg80211: All devices are disconnected, going to restore regulatory settings
[ 2140.607132] cfg80211: Restoring regulatory settings
[ 2140.607420] cfg80211: Calling CRDA to update world regulatory domain
[ 2141.948125] wlan0: authenticate with 68:7f:74:5e:42:ff
[ 2141.996396] wlan0: send auth to 68:7f:74:5e:42:ff (try 1/3)
[ 2141.998072] wlan0: authenticated
[ 2141.998877] rt73usb 1-1.2:1.0: wlan0: disabling HT due to WEP/TKIP use
[ 2141.998912] rt73usb 1-1.2:1.0: wlan0: disabling HT as WMM/QoS is not supported
[ 2142.035630] wlan0: associate with 68:7f:74:5e:42:ff (try 1/3)
[ 2142.037914] wlan0: RX AssocResp from 68:7f:74:5e:42:ff (capab=0x431 status=0 aid=20)
[ 2142.037943] wlan0: invalid AID value 0x14; bits 15:14 not set
[ 2142.057687] wlan0: associated