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- QQV03-20A a radiation-cooled split-anode tetrode made by Mullard and used in the 1940s, 1950s and 1960s as a V.H.F. frequency-doubler RF output stage with balanced output.
- QV05-25 a radiation-cooled output beam-tetrode made by Mullard. More commonly known as the famous 807.
- QE05-40 (otherwise known as the 6146) a radiation-cooled output beam-tetrode popular amongst radio amateurs as a final R.F. amplifier.
Read more about this topic: List Of Vacuum Tubes, European Designation (with American Equivalents)