On the Cover A bit of De Forest Radio Co. art from ca. 1931. It appears to be allegorical: the young Lee De Forest, being inspired to invent his Flame Audion, and the resulting, perfected S-bulbed triode. Of course, this month marks the 100th anniversary of successful tests of the first vacuum audions. In this...
Front Cover, Rear Cover Upper, & Rear Cover Lower Just Qvistad, LA9DL, and part of his tube collection. Various European receiving Tubes. The front row has the Lorenz DF41W at left, and a group of rare RFT (East German) miniature “gnome” types: EAA171, UCH171, UB171, etc. Rear row: three Loewe multi-unit tubes at left, two...
On the Cover Some “unborn” Kellogg AC tubes. As Alan Douglass describes them: A Friend just presented me with a cigar box containing these four specimens, along with poop sheets for the McCullough and Kellogg tubes. Evidently someone toured the plant and fished souvenirs from the scrap barrel. These look earlier than any finished tubes...
On the Cover “Life tests on continous evacuation of 304TL / March 8, 1943” Shows impromptu test rig at Eimac’s Salt Lake City plant. Subject: 304TL triode is at upper center of photo, attached to a vacuum manifold atop an oil diffusion pump. An ion-guage tube is on the same manifold, to the left. A...
On the Cover The “Liberty Valve” as once sold by the Radio Apparatus Co. of Pottstown, Pa In this issue
On the Cover Eduard Willi, Swiss tube-history author (see p. 2, depicted with a Signum G 2 H 34 rectifier. In this issue
The mount drawing for the now-eBaygenic “single-plate” 2A3 audio triode, with its 20 filaments. This original version carried a reputation for being hard to amke in terms of equal tension on the filaments, and was soon superseded by new designs. The note about the tensioning springs testifies to this diffuculty. Image: RCA Standardizing Notice 3-1-2A3,...
On the Cover The vanishingly rare GL-8009, a version of the 880 triode with two extra posts for the grid leads, introduced by GE in 1942. While “intended for television service’ on prewar tv channels, its frequency rating for full power was no more than that of the 880, or 25 MHz. In this issue
