The answer to the customer’s question below is that it makes absolutely no difference what brand the equipment is. Any gear that is connecting by a WiFi standard such as 802.11g or 802.11b can connect not only to any access point that is 802.11g or 802.11b, but also to an access point running in 802.11n mode (more modern) because 802.11n is backward compatible with 802.11g and 802.11b.
If you cannot connect, then the reason has to do with either security settings (most likely) or possibly the access point is not operating as a DHCP server (this is less commonly the issue): DHCP serves IP addresses to the client (USB WiFi adapter or internal wifi card) and if it is not running on the access point, then your client has no way of knowing what IP address scheme the network has and cannot automatically obtain an IP address, as is the more normal case. By default, all APs are in the mode of DHCP server, so it takes a conscious configuration change by the administrator for the AP to NOT be offering IP addresses to clients.
The exception is Ubiquiti gear that is running AirMax, which is a proprietary Ubiquiti protocol. However, Ubiquiti gear can operate as standard WiFi if AirMax is turned off: This is how you open a Ubiquiti Access Point for access by other-branded devices, and/or as a public or semi-public hotspot.
CUSTOMER’s QUESTION: You misunderstood, I think. I was referring to before, when I e-mailed you about not being to connect to an open nearby router, a DLINK WBR-2301, IIRC, with the Alfa. When i tried to connect with my laptop (Intel mini-pci wireless), it connectef fine. But both Alfas (AWUS036H and AWUS036EW) would not connect. I tried over and over, thinking it was that dhcp bug, but that didn’t seem to help.
Now, I want to send an Alfa adapter to a friend. He needs to connect to an open Belkin F9K1001 which is about 1000 feet away. Currently, he can connect using an Intel card built into his laptop, but I want him to have a stronger connectiong/lower latency. What is the likelihood that the Alfa may not like that Belkin router, the same way it didn’t seem to want to get along with in my own scenario above. I know in theory Wifi is always compatible, but I’ve read sometimes channel width, 802.11 mode, and other things can stop an adapter from connecting to a network. That’s what I’m asking about.