Right On, Spitoon
406 MHz is an international SAR frequency, primarily for beacons...and one reason is that all the new satellites used for SAR have 406 MHz receivers. Lower transmitter power and smaller antennas.
And you would never xmit VOX on 406MHz, as aviation UHF radios only select up to 400MHz. (Of course, with an old vacuum tube monster, you could cheat it a bit out of band.)