25-11-2016, 07:43 PM
The Acorn valve was good for RF, but extremely hard to make. Sylvania was maybe first in the USA with their button base "easy to make" Loctal (1938), very similar to EF50 concept (the Philips base had 9 pins but later they adopted the Sylvania base). Then in 1940 the mass production started of the RCA miniature button base B7G tubes. Used first in domestic Radios (USA didn't join war till Dec 1941, so very much domestic radio production in 1941), they were soon used in military. The German Telefunken had the much more clumsy Y8 base.
