Quadrotron

The Quadrotron tube was designed by Henry K Huppert while consulting engineer to the Baker Smith Company of San Francisco. Earlier in the 1920's Huppert had worked at the Atlantic-Pacific Radio Laboratories, where he developed the 2 in 1 and Solenoid tubes. Radio News for July 1926 carried a two page article (pages 50 and 51), where he described the Quadrotron tube in some detail. He detailed his experiments with what he called ultimate requirements which lead to his work on a better capacity of operation. The new tube apparently minimised grid to plate capacity and this was half that of the standard 201A type. This was achieved by the addition of a fourth element in the form of a small sheet meal triangle. This was placed in the same plane as the filament but inside it. The tube press in the illustrations clearly show that five wires pass through it. The extra wire was connected to the triangle (or fourth element) but where this emerged was not shown in any of the illustrations of the tube. In an article written by Gerald Tyne for the Antique Wireless Association (Vol 14, No 4, Page 23, 1974, there is a diagram of the tube with a side screw terminal. Tyne states that he added this himself. He also states that the tube, as far as he knew, was not advertised in any radio journals. No patent has so far been found. Page 361 of Tyne's "Saga of the Vacuum Tube" lists the Quadrotron as being made by Baker Smith Co, who also made Sylfan tubes.

History of this tube is covered extensively in the article "Henry K Huppert and his Tubes" etc by Eric P. Wenaas, which is in The Antique Wireless Association's Review, Volume 30, 2017, pages 173 -222.