After returning from a field exercise, what is the last step when securing the AN/PRC-77 radio?

Turning the operating controls to clear the last frequency used is a critical step in securing the AN/PRC-77 radio after a field exercise. This procedure ensures that the radio is reset to a neutral state, minimizing the risk of accidentally transmitting on an incorrect frequency in the future. It helps maintain operational security and prevent potential incidents that could arise from using a previously set frequency without proper clearance or coordination.

When the last frequency is cleared, it also allows for smoother operation the next time the radio is used, as it prevents confusion regarding which frequencies are available. This practice is particularly important in maintaining communication discipline and security protocols, which are essential in military operations.

While the other options such as removing the battery, disconnecting the antenna, and wrapping the handset correctly are important for the overall care and maintenance of the equipment, they do not specifically address the immediate operational readiness and security aspects that come with ensuring the radio is operating on the intended frequencies.