I purchased a SparkLAN WUBR-505N dual band USB WiFi adapter, which claimed to do 802.11 a/b/g/n, for my Powerbook G4. This card is using the Ralink RT 2870, which is a dual band chipset with fairly nice Mac OS X drivers provided by Ralink. I plugged it in and tested it with my existing network configuration at 802.11n (802.11b/g compatible) 2.4 Ghz, and it worked beautifully.
Unfortunately, once I switched my AirPort Express to "802.11n only (5 Ghz)", the Ralink no longer saw my WiFi network. Repeated rescans with the Ralink Wireless Utility could not detect the network, and manually inputting the SSID did not work either.
I need a way to get the Ralink RT2870 based SparkLAN WUBR-505N working with 5Ghz mode on the Apple AirPort Express.
#90: 5Ghz mode with Ralink RT2870 and AirPort Express
Solved!on April 06, 2010, 01:20 AM UTC — from 
yliu ( 5,878 views )
yliu ( 5,878 views )
Must use a lower channel than 149
- yliu on April 06, 2010, 01:28 AM UTC
The Ralink RT2870 works with the 5 Ghz band on 802.11n, but it has specific channel requirements.
The main trick here is that by default, the AirPort Express will set its wireless channel in 5 Ghz automatically. In fact, the only choice under "Channel" in AirPort Utility is Automatic, and it usually chooses channel 149. Apparently this is out of range for the Ralink RT2870. At high channel, the Ralink card will not detect the 5 Ghz network.
If you hold down the Option key while clicking on the Channel pop-up menu, you can manually set preferred channels. Set it to a low channel, such as 36, and reboot the router. When it comes back up, the Ralink should pick up the 5Ghz network when you scan again.
The main trick here is that by default, the AirPort Express will set its wireless channel in 5 Ghz automatically. In fact, the only choice under "Channel" in AirPort Utility is Automatic, and it usually chooses channel 149. Apparently this is out of range for the Ralink RT2870. At high channel, the Ralink card will not detect the 5 Ghz network.
If you hold down the Option key while clicking on the Channel pop-up menu, you can manually set preferred channels. Set it to a low channel, such as 36, and reboot the router. When it comes back up, the Ralink should pick up the 5Ghz network when you scan again.
References used:
5GHZ Airport Success!
( http://sentman.com/users/james/weblog/b5130/5GHZ_Airport_Success!.html ) - found by
yliu on April 06, 2010, 01:23 AM UTC
Think you've got a better solution? Help yliu out by posting your solution
5GHZ Airport Success!
http://sentman.com/users/james/weblog/b5130/5GHZ_Airport_Success!.html - found by yliu on April 06, 2010, 01:23 AM UTC
how to switch channels on the 5 Ghz range in AirPort Utility
Re: WUSB600N does not detect the 5GHz band on my W... - Cisco Home Community
http://homecommunity.cisco.com/t5/Wireless-Adapters/WUSB600N-does-not-detect-the-5GHz-band-on-my-WRT610N-router/m-p/312410 - found by yliu on April 06, 2010, 01:23 AM UTC
Post by ReginaldPerrin is informative. The WUSB600N uses the same RT2870 chipset, and only works with low-number channels in the 5 Ghz range.
Comments
I cannot get the Wifi N mode to work on my ralink RT2870 chip, it is set to 2.4G and greyed out (cannot be modified). I have a time capsule on the other end, which is N enabled.
— cybercap on May 20, 2010, 09:21 AM UTCI am having the same problem with the RT2870. I contacted Buffalo and they told me that it is capable of channels above 11, but only with their Windows driver. So unfortunately this is a limitation of the Ralink software. I will try to contact them, but they are in China and I'm in California
— Andrew H. on December 30, 2010, 01:58 AM UTC