I even know how to make a tube out of a dual filament car taillight.
Now there's a real tube.

I, too, would like to see a circuit which demonstrates that "tube"
did something useful. Is it just a diode (i.e., rectifier), or
can it also amplify?

--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
NRA Life Member and Rifle, Pistol, & Home Firearm Safety Certified Instructor
Certified Instructor for the Kansas Concealed-Carry Handgun license