Not sure why you are downvoted, it's the most relevant and humorous explanation of the calm, professional ATC "Houston Center" voice out there.
https://np.reddit.com/r/todayilearned/comments/8x5ndw/til_wh...
Wait...military planes only have a single radio receiver? Military spy planes only have a single radio receiver?
This seems a perfectly sensible thing for the RSO to do on a training mission, since on a real mission he might need to monitor multiple frequencies:
> I was beginning to feel a bit sorry for Walter in the back seat. There he was, with no really good view of the incredible sights before us, tasked with monitoring four different radios. This was good practice for him for when we began flying real missions, when a priority transmission from headquarters could be vital
At this point, they have passed their hours threshold and are heading back home. The pilot says:
> Just to get a sense of what Walt had to contend with, I pulled the radio toggle switches and monitored the frequencies along with him.
For redundancy they have multiple Transceivers, and most military radios cover both VHF and UHF.
For safety and redundancy the pilots can receive and transmit on any of their multiple radios just by (selecting the appropriate frequency) and pressing the appropriate Receive/Transmit selector buttons.
Many military aircraft also have secure (spread-spectrum) transceivers as separate units.
Many aircraft that fly over water also have VHF Marine radios fitted.