Modern vacuum tube collectors have been trying to find concrete evidence that the DeForest Type 20 was not only made but designated type 20. This author believes he has found what has been missing or perhaps re-found again within my information?

As all collectors know, Otis Moorhead was the first to bring together DeForest and, Marconi and create a working agreement to break the deadlock of the patent situation following WW1 that essentially meant that no maker could legally make and sell triode vacuum tubes. DeForest saw an opportunity to market a few of his own tubes as well as abide by the terms of the DeForest, Marconi, and Moorhead agreements. This arrangement was embraced by at least Moorhead as DeForest tubes were quite popular with the US military and amateurs alike and provided an outlet for more sales by the Pacific Radio Supplies Company.

Click on the ad and tube pictures below for a large version

The first DeForest made tube to be offered of this new partnership was the Type 20. Of course, the new DeForest tube had to have been made many months before but the first, and possibly only advertisement, in fig. 1, appeared in the Electrical Experimentor in May, 1920. While no picture is included in the ad, it is identifying the offering as the type 20 several times. Marconi cancelled its contract with Moorhead, DeForest, and Marconi contract in July, 1920 so it could be presumed that DeForest never had a chance to sell his stock of type 20 tubes, or very few. These type 20 tubes can be ID’ed by having a shiny nickel base with only the words “Patent Applied For” stamped on the base and “DeForest” etched in a circle on the top of the glass bulb.

This author contends that DeForest type 20 tubes were re-released in early 1923 and became several different versions of what became the DV 6. The later version DV 6 had the same nickel base but the word “For” was dropped along with the etching word “DeForest”. Patent numbers were added along with the words “Sold Only for Amateur and Experimental Use”. Two distinctly different versions.

Please see the tube pictures below along with a description of each.

Fig. 2. The DeForest type 20 tube first offered for sale in May, 1920. I do not own the second version of the type 20 but one can be seen on Bill Condon’s site.

Fig. 3 This would be the box for the re-issued type 20 that was called the DV-6, later version in 1923 and would be the shipping box for the DV-6 on Condon’s site.. This was the soft version as well.

Fig. 4. DeForest added the DV-6A and advertised it in Sept., 1923. This was the hard version.

Click on document below to enlarge

The January, 1947 issue of Radiocraft magazine featured a tribute to Lee DeForest. Within those pages, George Clark, (1880-1950) famous collector, played a personal tribute to DeForest. Fig. 7

An unknown picture taken by Gerlad Tyne is one that Clark choose to include.

As can be seen in that picture are two, what Clark calls, type 20 tubes along with one version of the WW1 DeForest VT 21 on the left.

I think Clark mis-identified the tube on the far right as a type 20 when clearly, it’s a DV-6A. Never-the -less, I am in no position to second guess Clark calling the tube in the middle a DeForest type 20, which it is.

Here is the entire magazine article in fig 7 as it relates to DeForest here: RAD47

Figs. 5 & 6. 5 is the early short version VT 21 that came from the Edwin Armstrong collection via Tyne. 6 is the later version of the DeForest Vt 21.