IO540
That's a bit harsh on Bose, and I believe that he is correct. The two freqs do not need to be next door to each other... its more a question of harmonics and spacing of the aerials. On most light a/c their isn't enough real estate to get the aerials far enough apart. Even on my state of the art DA42 the G1000 is capable of splitting the comms, i.e allowing pilot to talk on one freq and co-pilot to talk on another, but this isn't recommended by Garmin as the aerials are not far enough apart. (Yes I know that it wasn't quite the original point here, but its the same sort of thing)
3Y