I want to buy a WiFi USB adapter which would allow me to monitor the packets using tshark, and it should preferably be cheap. I'd also want to know if there are cheap WiFi USB adapter with antenna under 8-9 US$.

  • Hi there, unfortunately your question has been put on hold because it asks for shopping recommendations. These style of questions are not allowed here as they generally lead to extended discussion and are often very subjective. – Jivings Feb 6 '14 at 8:34

There's a list of wifi adapters that work with the pi here.

I'm sure you can manage to shop for them online yourself. Under $8-9 US is probably a little low, but there are many of them in the $10-15 range. I would not worry about an antenna, the pi USB ports are underpowered so you want a small adapter, unless you attach a powered hub.

  • Do all the adapters listed in your link work in monitor mode? Also, do I really need a hub, can't I use 5 Ampere power, would that not work when using antenna with USB WiFi adapter? – Ouroboros Jan 17 '14 at 19:32
  • I didn't write the list, so whatever it says there is what it says. It doesn't matter what size power supply you use, you won't get more than ~150 mA out of the pi's USB connectors. I don't actually know if an antenna really requires more power, but since they are used to transmit as well as receive, I'm presuming they do. Check the power requirements, and opt for one on the low side if you don't want to use a hub. – goldilocks Jan 17 '14 at 19:36
  • Can you please explain how powered hub allows us to use WiFi Adapter with antenna, and not higher ampere of power? I am no electronics expert, but if as you say USB won't get more than 150 mA, what is it that hub does to do that? – Ouroboros Jan 17 '14 at 19:49
  • USB 2.0 is supposed to provide 500 mA to a connected device, but the pi is limited to 150 mA. See the third paragraph here (starting "Each of the two USB ports..."). I have a newer pi without the polyfuses, but it is still underpowered at the ports although my supply is 3.7 A (perhaps because of paragraph 4, "The microUSB input port also has a 1.1 A polyfuse"??). If you use a powered hub and plug the wifi adapter into the hub, you will get power from the hub and this won't be a problem. Don't count on the pi's USB ports for much. – goldilocks Jan 17 '14 at 20:17
  • Thanks a lot goldilocks. I'd like to know if newer pi's still have this problem, or if the 150 mA limit has been improved upon. – Ouroboros Jan 17 '14 at 20:30

You must to think about the distance between the router and the Rapsberry. Small wifi adapters doesn't have a good signal reception (due the size of antenna).

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