As far as I am aware, a radio signal is basically just shouting into the void, and anyone who is tuned to the correct channel can hear you clear as day, like a car radio. So, how do militaries keep their radio signals from being over heard by the enemy? Do they have special radios, or are the communications sent over radios just not that important strategically?
In: Technology
Not only do they generally not try to stop the radio signal being overheard (except for exotic things like frequency hopping like /u/tezoatlipoca mentions, although that’s more for anti-jamming), they *assume* that the enemy will intercept all your radio transmissions. Like you said, you’re just shouting into the void.
So they don’t do a ton to secure the radio signal itself for security (you might want to do that for other reasons, like stealth). Just assume the enemy will receive everything you broadcast. So the key is to make sure they can’t so anything useful with it…and that’s where encryption comes in. The encryption has nothing to do with the radio signal itself, it has everything to do with *what* you transmit over that signal. The enemy can intercept everything you send, but they’re intercepting an encrypted signal. Without the decryption keys, it’s gibberish to them.
Not much has changed, architecturally, since the time of WWII and the Enigma machine. The encryption has just gotten better.
This also has the added benefit that, once you have good encryption, you don’t have to care very much about how you transmit it. You can send it over radio, SMS, email, newspaper, morse code, take out a billboard, put it on craigslist…as long as the encryption is secure, you can use a totally unsecure transmission channel.
Edit:typo
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