I 'knew' Bill Orr, W6SAI (SK), like most hams, through his numerous articles and books, though I did correspond with him on one occasion (a technical question).
///
The reason for this entry is that I just realized that 2017 is the 50th anniversary for a series of amplifier (vacuum tube of course) articles that appeared in 1967 issues of 'QST'.
(I was a high school kid back then and the text and graphs burned their way into my memory ... I still smile.)
///
If you're not familiar with the wonderful articles published in 'QST' by W6SAI, and some of the other hams at EIMAC (free advertising really but still great articles), take the time and use the ARRL's on-line search feature (for members) of 2011, and earlier, issues of 'QST'.
///
Some 'QST' Amplifier articles by W6SAI :
///
The Grounded-Grid Linear Amplifier; Aug 1961
///
Intermodulation Distortion in Linear Amplifiers; Sep 1963
///
The Cathode-Driven Linear Amplifier; Jun 1967
///
Semi-and Super-Cathode-Driven Amplifiers; Jul 1967
///
Forced-Air Cooling of Transmitting Tubes; Sep 1967
///
(signed) Paul N. Nix, WB5AGF (23 Mar 2017)