Permission to reproduce these articles here was kindly given by the American Radio Relay League, 73 Magazine and in the later case the author(s) of the original articles as well. You can find the ARRL website here.
If you did not see it already the main sweep tube page is here
From August 1975 73 Magazine, used with permission
Used with permission from February 1980 QST; copyright ARRL
Used with permission from October 1974 QST; copyright ARRL