Several techniques exist, but [Wolfgang] over at the Electronic Projects for Fun blog decided to go for the classic method of using a vacuum diode. He describes the design and analysis of a noise ...

That's when a British scientist named John A. Fleming made a vacuum tube known today as a diode. Then the diode was known as a "valve," because it forced current in the tube to travel exclusively ...

In other words, it can become a diode of sorts, in a manner reminiscent of a vacuum tube diode. [Paul Stoffregen] has made use of this phenomenon in a flame detector that he’s built to be ...

"I have been receiving signals on an aerial with nothing but a mirror galvanometer and my device." The device was the original thermionic vacuum diode ...