Ken-Rad stood for Kentucky Radio - it was based in Owenboro, Kentucky. It was an active second-tier tube company before World War II, and during the war was a major tube manufacturer. In 1945 Ken-Rad was bought by General Electric, and became GE's receiving tube division. The Ken-Rad name continued to be used into the early 1950s, but was then replaced by General Electric. The documents here only cover the pre-1945 era, later Ken-Rad documents are listed in the General Electric section.
The 6L6 Beam Power Amplifier - Description of the new 6L6 as well as extensive notes on operation. Lots of curves showing the performance under different conditions.
Operation Characteristics of the 6L7 - Description and operation of the 6L7 pentagrid mixer tube.