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
The answer is encryption. Modern radio systems transmit sound as digital information and the data is encrypted.
It is not in principle that different from how it is done with cellphones. The link between you and the cellular tower is encrypted so no one else can understand unless they break the encryption and find the key.
The problem for the military system is that you need a way to distribute the key to all parties on that network who have it and can listen to the radio. Most radio communication is done within a unit so you can physically transfer the key. In some system, you connect an electronic device to the radio and in other you enter it by hand.
Historically it was a lot harder and the common radios had no encryption built-in. So you could encrypt text by an external device and transmit it often with morse code and then decrypt it on the other end. This will result in time delay so impractical in lots of situations.
In WWII US used [Code_talkers](https://en.wikipedia.org/wiki/Code_talker) primary in the pacific. The user Native American that spoke in their own languages. The languages were quite unknown to the outside world so the Japanese did never understand it
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