Technical Articles
The Story of the Super-Heterodyne PDF (17.3M)
Its origin, development and some recent improvement - A Radio Club of
America paper
by Edwin H.Armstrong, Marcellus Hartley Research Laboratory,
Columbia University, New York
Published in Radio Broadcast, July 1924.
Vacuum Tubes and Their Uses PDF (.6M)
Includes a non-technical explanation of the operation of the vacuum tube.
by M.L. Muhleman
Published in Radio News, August 1926.