Mulitiple wifi connections on Macbook I have an external, long range, wifi antenna that I use for picking up internet and I also have a wireless nmea network on my boat for my marine instruments.  The problem that I am experiencing is that I must disconnect from my nmea network in order to get anywhere on the internet because when I have both wifi nets active, the Macbook Pro wants to use the nmea network to connect to the internet and it can't.  It doesn't matter which way I connect [internet on airport/nmea on external, or the other way around] the internet is inaccessible when the nmea net is active.

Can I make it so that the internet will only come through the external antenna and the nmea net will only come through airport?

Thanks for any help
If the external wifi device shows up in system preferences network pane, ensure that the internal adapter is above it in the "set service order" dialog (get to this by clicking the gear icon near the bottom left corner and selecting "set service order")

Do note that some external wifi devices do not show up in system preferences or don't obey this setting, so YMMV. If it doesn't show up or doesn't obey the service order, your only option would probably be to change it manually in Terminal.

Note that if you don't have a valid IP address on one of them it will automatically be lower than one that does.

Also, if the two networks also share the same IP scheme (ex 192.168.1.xxx), the computer might be getting confused by this. The way you describe this makes me think this is the problem, but service order is also a distinct possibility.