Here is one example that works with ANY analog (ham) radio:

1. Load up a wallet (12 words)

2. Encrypt (256 / 448 bit) the seed

3. Get cheap baofeng radio

4. Get Rattlegram app

5. Paste encrypted seed in Rattlegram

6. Press push to talk button radio

7. Transmit encrypted seed over radio

Encrypted message is being modulated and can be received with same setup on the receiving end , both parties have to know the encryption key. https://youtu.be/AfCigNQIZRc