[Amps] config cathode-drive Amp with a Tetrode?

[Ian White, G3SEK]

G & M Johansson wrote:
>How should a proper schematic configuration of a cathode-driven Amp
>be done with a Tetrode ?
>
>I've seen a couple of variations:
>
>1) Both grid, Screen grounded
>(guess its a common way of solving it....
> Also described in the book:
>Power Vacuum Tubes Handbook, 2nd ed)
>
>2) Grid to ground , Screen to DC-screen -voltage
>(a few russian schematics)
>
>3) Grid to Cathode, Screen grounded
>(from AG6K's excellent site)
>
>Which one is the 'proper' way to do it?
>
>Does it depend on what kind of tube being used?

Option 1 will work with some tubes, but it is not what the original tube 
designer intended (g1 and g2 of a tetrode are supposed to be at 
different potentials). Some tubes will handle this type of operation, 
but most modern tetrodes will not, because the g1 current is too high.

Likewise option 3 is not what the tube designer intended.

There are at least three other options that do use the tube 
manufacturer's recommended g1-cathode and g2-cathode potentials. There 
is a downloadable explanation at 
http://www.ifwtech.com/g3sek/boards/tetrode/an-4-1.0.pdf
This is an extract from the Tetrode Boards manual; it includes 
schematics that show the various options for DC and RF grounding, and 
how the g2 and g2 supplies should then be connected.

-- 
73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                           'In Practice' columnist for RadCom (RSGB)
                            http://www.ifwtech.com/g3sek