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
One, the data of the signal is encrypted. Two, the radio signal jumps around on different frequencies seemingly randomly, hard to get the whole signal. Military radio operators “key up” at regular intervals so their radio knows the correct encryption and frequencies.
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
Generally speaking all military radio communications are secured by encryption. In the old days, encryption was performed by an add-on device. Generally speaking, modern radio devices have embedded encryption circuits.
They’re encrypted for one (digitally) and they channel or frequency hop – in a seemingly random manner, but if you know the seed and the algorithm, a computer can follow it.
The channel/frequency hopping while part of a security measure is also good to battle against jamming and electronic countermeasures although most ECM suites can probably track/jam a frequency hopping signal too.
The actual technology is very much ”If you know it you dont talk of it” But the basic encryption is just using an algorithm to scramble the message and Send it through multiple predefined frequencies. Unless your receiving end knows the exact sequence all they hear is static mess- even if listening to every frequency in the sequence simultaneously.
Note; this doesnt mean it cannot be intercepted, So your very basic trigonometry can still locate the source If the transmission; hence brevity (short transmissions) and sometimes built-in scrambling that sends the whole bunch as a shorter-duration pulse.
But; radios are just one part of comms, and rest of it goes past ELI5 level.
Lots of the communication out there, both military and civilian, are encrypted.
Basic encryption can just be taking a single word and shifting all the letters over by one. ONE > POF. The encryption used in communications takes this concept to a manageable extreme.
So long as both sides know what was used to encrypt the message, they can decrypt the message. POF > ONE.
The radios are special but the methods are common to consumer electronics, but just more robust.
Encryption is just part of the process. On top of that, communications data is [chopped up and sent through different frequencies at once.](https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum)
Only if the receiver knows which frequencies at which times are transmitting the right information can it even begin to decrypt.
And that’s just the handheld stuff.
Sometimes its also just a matter of having a literal set of wires, carefully guarded, that only goes from point A to point B. Nobody but A and B will know.
It depends. There are a couple of methods. One of the larger/more general ones is encryption. There are many different ways it is implemented. There are dedicated radio encryption devices as well as radios with encryption built into them.
Additionally there are other technologies such as frequency hopping that make it difficult to find out exactly what frequency is being used at any given time.
Edit: something else is also not talking about certain things on the radio. Somethings should not be communicated over radio (because it is so much less secure than other things). Or you can use code words. So instead of saying “Switch to frequency 100.1” you would say “Use Banana Boat.”
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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