TREE FIFE FOWER NINER predate ICAO for a long time. Military origins.
Before you talk about how this dates from crappy radio days, understand that the aviation VHF radio is still the same crappy full-carrier AM system with compatibility with old telephone equipment that we were using over a half century ago.
Before you talk about how this dates from crappy radio days, understand that the aviation VHF radio is still the same crappy full-carrier AM system with compatibility with old telephone equipment that we were using over a half century ago.