First, thanks for this great program, really nice to find free channels and to optimize signal strength for my own network.

As I'm sure you know, the valid channels vary around the world - especially in the 5 ghz band.
I suggest you make a simple 'Region selection', and then show the valid channels for that region (enabled color).
Today, the channels shown are only for U.S.
It will help especially new users to find free legal channels. Here in Europe, it's actually quite confusing, which channels are actually valid.