Some new research on using Lithium Niobate rods via the piezoelectric effect as a short transmitting antenna for VLF/ELF/ULF frequencies. The nature article below points out the Shannon–Hartley limitations on bit-rate at VLF can be overcome - meaning that larger amounts of data can be transmitted than with conventional antennas at these frequencies as the antenna is directly modulated mechanically. Interesting read! From the Journal Nature (Nature Communications) https://www.nature.com/articles/s41467-019-09680-2 A simplified explanation https://www6.slac.stanford.edu/news...-antenna-communicating-where-radios-fail.aspx
Build the piezo crystals into a mechanical "sounder" key, you'd have a NON-Electronic radio transmitter. No batteries required. A hammer ,a crystal and a ground rod... On the air.
Crude version of a Piezo Long Wave Transmitter: Football size chunk of Quartz at the beach, employ " Percussive Modulation" with a fist sized stone. I'll bet a sensitive receiver would hear that at some distance.
