This from Wikipedia➙ Homebrew is an amateur radio slang term for home-built, noncommercial radio equipment. Design and construction of equipment from first principles is valued by amateur radio hobbyists, known as "hams", for educational value, and to allow experimentation and development of techniques or levels of performance not readily available as commercial products. Some items can be home-brewed at similar or lower cost than purchased equivalents. (There are some interesting links at the bottom of this page)
Homebrew Radio Gear On The Web (External links open in a new browser window)
14 Tube Receiver➙ Uses octal base tubes and includes a crystal phasing filter plus calibrator.
K5UJ➙ Rob's pair of 4-400's modulated by a pair of 572Bs