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I have an outdoor application including an RPi3 which requires connecting to an xfinity wifi hotspot but the signal is weak. Therefore I tried adding a USB wifi dongle with antenna to improve connectivity.

I bought two of these: EDUP Wireless N Adapter 300Mbps 2.4GHz

They are plug and play and I had no problem connecting to xfinitywifi and logging in from the browser. I did however have to disable the onboard wifi interface sudo ifdown wlan0 as both modules were connecting at the same time.

The problem now is that despite the specs on the USB dongle and the better signal quality, we get roughly 4-5 times lower upload/download speeds, compared to the built-in wifi module!

Here are some speed tests, ran on speedtest.net. We tried 2 of these dongles and the results were similar (so it's unlikely the module is faulty)

Here is the iwconfig for USB dongle:

      IEEE 802.11bgn  ESSID:"xfinitywifi"  Nickname:"<WIFI@REALTEK>"
      Mode:Managed  Frequency:2.437 GHz  Access Point: AE:34:26:27:68:36
      Bit Rate:144.4 Mb/s   Sensitivity:0/0
      Retry:off   RTS thr:off   Fragment thr:off
      Power Management:off
      Link Quality=96/100  Signal level=55/100  Noise level=0/100
      Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Here is the iwconfig output for built-in wifi module:

      IEEE 802.11  ESSID:"xfinitywifi"
      Mode:Managed  Frequency:2.412 GHz  Access Point: 0E:51:A4:D3:F1:D2
      Bit Rate=72.2 Mb/s   Tx-Power=31 dBm
      Retry short limit:7   RTS thr:off   Fragment thr:off
      Power Management:on
      Link Quality=55/70  Signal level=-55 dBm
      Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
      Tx excessive retries:18  Invalid misc:0   Missed beacon:0
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    The onboard WiFi is connected by sdio with potentially much higher throughput than external dongles, which share the USB2 hub with other peripherals. – Milliways Dec 6 '17 at 22:18
  • So the only other solution is the external antenna mod that could potentially violate FCC regulations? That's not neat :/ – cvb0rg Dec 7 '17 at 15:54
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Here is a forum that talks about the range issues. The general sentiment on that forum seems to point that the range on the Raspberry Pi 3 WiFi does not seem to be as good as the USB Wi-Fi Dongle. Other places I have read have said that the Wi-Fi Dongle is not as fast as the onboard Wi-Fi. I guess it could depend on your priorities. Do you want long range or fast?

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