Nice post, HighPlains. I just want to add a short note regarding the 2 frequencies mentioned in Dan's query. You mentioned them "This radio set selects two of these 1 MHz slots to operate on," but didn't mention why. The reason lies in the method chosen to deal with the issue of antenna directivity and blockage from the required direct path (at cm wavelengths) to the Tx by vehicle structure as it maneuvers. Two antennas are used and located such that at least one of them has a direct path view. Here is where the design choice comes in: two receivers are used, vs switching one receiver between the two antennas. It is easier to implement than switching between antennas, at the cost of requiring twice the bandwidth - the entire RF path is redundant. Some other systems do switch antennas to deal with the same blockage issue - the EHF SATCOM suite that is deployed on all USN ships larger than frigates, for example.

Abel

Edited to add antenna directivity. Our usual omni antennas are omnidirectional only in one plane