Hertz electromagnetic wave experiments  Updated 2025-07-16
Heinrich Hertz's main initial experiment used a spark-gap transmitter. It is not something that transmits recorded sounds like voice: it only transmits noisy beeps. And as such was used for wireless telegraphy.
- a piezo igniter from a barbequeue lighter
 - a more powerful home-made transformer
 
Hertz and Radio waves Explained by PhysicsHigh (2016)
 Source. Simple schematics showing the basics of the experiments. No choice of components rationale.