The 5 Transistor ESR as detailed on the EEVBlog forum.
I have created this project and made up a through hole version of the PCB as part of my Amateur Radio training / Exams.
Feel free to review / use this project. It is not my design that credit goes to Jay_Diddy_B over on the EEVBlog.
73 Paul M6KUR
Tube Based Amateur HF / Shortwave Transmitter Project
Similar to the Pine Board Project by Bob Heil.
Untested. Use at own risk.