> ? No tetrode can be used in such a way to produce a practical linear
> amplifier. Tetrodes are designed to be grid driven using a regulated
> screen supply. They work best when neutralized and not driven into the
> grid current region. However, only tetrodes that are designed for Class
> AB1 will work well. The 4-400A and 4-250A were designed for Class AB!.
> The 304TH and 833A were designed for Class C operation -- i.e., they
> will only draw the rated current with substantial grid current, and that
> makes ssb doo-doo in AB1.
The 304TH and 833A are moderate mu triodes, not tetrodes. They are
specified for grid driven, AB2 (linear) service ... regularly used
as both modulator and PA tubes in AM broadcast transmitters of the
60s and 70s.
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