majoco
Stirrer
As far as I recall, going back to the 60's when I was a marine radio officer, VHF radios had to be 'idiot proof', so that they could be used in an emergency by any unskilled person on the bridge of a ship. One switch for Ch.16 and a fixed squelch and volume so that it could not be muted. You could select any channel number, but not frequencies, you didn't need to know anything, the coast radio station would tell you the working channel to switch to, usually 21 or 22. No need for callsigns, the call was the ship name. Certainly no out-of-band selection.