[E. Pluribus Unum]

You can make a transmitter and receiver that use visible light. It used to be a science project experiment with a light bulb that flickered when you spoke into the microphone and a receiver that used a photocell to convert the amplitude-modulated light waves into an electrical signal that would be amplified and output to a speaker.

But you're right. Your shortwave receiver won't pick it up, because it's tuned to a different range of frequencies.

[Dr. Bogus Pachysandra]

” It used to be a science project experiment with a light bulb that flickered when you spoke into the microphone and a receiver that used a photocell to convert the amplitude-modulated light waves into an electrical signal that would be amplified and output to a speaker.”

Hmmmm,,, Seems just about like the Tremolo/Vibrate-oh in my 64 Fender Vibroverb! But we call the parts “The Roach.”