Josh,
Thank you for clearing that up - I had a feeling you meant multiplexed (as a TACAMO plane transmitting music on a UHF military frequency makes little sense to me). So they simply use chunks of the vast 225-400 MHz band and multiplex voice/data on a wideband carrier, switching frequencies as they move and/or as the operational conditions warrant. Sounds like you've got a good monitoring location and setup. Naturally these guys are running power and high gain antennas. Even without those, they're 40,000 feet up, as you've said.