I blame the intentionally cheap receiving optics. Researchers have reconstructed a TV signal from a hotel room with closed blinds, by very accurately measuring the ambient light intensity of the room (as shown on the blinds.)

Knowing that, I doubt that someone with even moderate funding would have difficulty receiving a signal from any of the transmitters you mention.

But, in all honesty, if you put a physical cap on the transmitter and receiver, maybe I'm wrong.

But in the other hand, none of the devices I currently own have one of your transmitters, and they all have screens and cameras, so...

Thanks for the dialogue and for sharing your experiences.