On the Cover A Western Electric 240A with the radiator and anode cut away to show internal construction. Note that the water inlet and oulet fittings are displaced from each other, presumably to induce a spiral flow of the colling water. Photo from the late Bell Labs Historical Museum. In this issue
On the Cover The Eimac X-O from early 1942, first of a numbered line of “X” developmenta types that eventually ran into the low thousands, and one of the umpteen possibilities that eventually yielded the 527 radar triode. It appears to use th eduel stacked anode assembly and grids from the VT-158 Zahl tube, in...
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...