Radio Communication with Airfields

I've noticed on both Nevada and Normandy, the Airfields primary radio frequency is either above or below the radio frequency range of the Mustang. So I've been using the 2nd listed radio frequency, but doing this seems to grey out every airfield in the communications list even if it is correct and I can send and receive communication. Am I doing something wrong when I create my missions or is there a correct way to setup the radio for the mustang?

That's easy comms for you. I'm going to guess that easy comms only understands the primary (VHF) frequency for ATC.

No, you're not doing anything wrong. Your radio only operates in a certain frequency range and you must use the frequency for that airfield which your radio can tune. My suggestion is to not use easy comms and not join any server which forces it on.

EDIT: I was wrong. SCR-522A radio is capable of 100-156MHz inclusive. I don't understand why the manual says the radio can do 5 channels when there are only 4 buttons (A B C D). In any case easy comms shows that "correct" frequency is 257.95 MHz which is a valid frequency to use but the airplane cannot do it. Even if I have 124.75 MHz (correct MHz) easy comms compares 124.75 with 257.95 and thinks because they are different, no good, color black in menu.

More in depth easy comms will choose the channel which is valid for the selection even if the selection's "white" frequency isn't the same as the VHF frequency it will pick. Example: Tonopah Test Range shows black text "257.95". I have 124.75 as channel "D". I choose channel "A" and then request start up. Easy comms automatically switches me to channel D and comms are a success.

However if I didn't have 124.75 anywhere on A B C D then it is impossible for easy comms to tune your radio to a valid frequency (previously easy comms would choose from frequencies your radio can do even if it wasn't a preset).

So basically ignore the black text if the text color frequency matching is outside your able frequencies. It will change your radio channel letter if it can. You'll only get white text if your current frequency matches exactly the frequency displayed on the menu. There should be another color of text, gray, which represents not tuned and impossible to tune. This feature is not working.