The content is encrypted with one-time pads that are constantly refreshed, which is entirely undecipherable through cryptanalysis. Encrypting the radio signal

The content is encrypted with one-time pads that are constantly refreshed, which is entirely undecipherable through cryptanalysis. Encrypting the radio signal itself would require a much more extensive infrastructure than binders and radio receivers: specialized hardware that might be compromised or flawed, or simply break down, rendering you unable to listen to the channel over which your critical orders might come; harder to audit as well with more moving parts and components that aren't easily inspected or tested. This seems like a case of a very simple and robust system being more than sufficient for the task, and anything more complex is a waste of time and money.