[Amps] Re: matching network

[R.Measures]

>One further clarification, in grid driven configuration: yes, the screen is 
>grounded for r.f. but so is the cathode (less so if a degeneration 
>resistor is 
>used), so the drive is still applied between the grid and cathode. 
>
>If the peak drive voltage exceeds the bias voltage, grid current will flow. 
>If not, then grid current will not flow. This happens in grid driven or 
>cathode 
>driven service. The grid current curves for a TH347 (the tube I have most 
>tested) , in cathode driven service, seem to be independent of actual screen 
>voltage and plate voltage.
>
**  When no drive potential exists between the screen and the grid, the 
tetrode acts as a triode.  This is why applying DC screen potential to a 
g-g tetrode does not increase amplification or reduce the drive 
requirement.

>...