17 ms·

I'm really surprised ELF are not commonly used for this. Even a simple single-frequency CW transmitter for emergencies. I wonder if audio frequencies below 20K

I'm really surprised ELF are not commonly used for this. Even a simple single-frequency CW transmitter for emergencies. I wonder if audio frequencies below 20KHz can be used to make a cheaper system.

ttyprintk 5y ago
At the extremity of that band, fewer nations have constructed transmitters than have nuclear weaponry. You can combine acoustic with radio in TARF (yes, really).
- goodpoint 5y ago
  I meant acoustic frequencies in ELF, not using sound... but TARF looks amazing.
- ale42 5y ago
  see e.g. https://www.mit.edu/~fadel/papers/TARF-paper.pdf https://www.mit.edu/~fadel/papers/TARF-paper.pdf for those who didn't hear about TARF (translational acoustic-RF communication)