[Amps] Grounded Screen 4CX1500B

[R.Measures]

On Nov 7, 2005, at 8:38 AM, Ian White G/GM3SEK wrote:

> R. Measures wrote:
>>
>> The 30S-1 is cathode-driven because  no signal applied between the 
>> grid
>> and the cathode.
>>
> It is cathode-driven because the RF input is connected to the cathode -
> and nothing else (still looking at the schematic here).
>
>>> I could never see how a 4CX1000A could function well in a
>>> grounded grid mode.
>>
>> The screen grid is grounded
>
> Yes...
>
>> and the control grid is at the same signal potential as the cathode.
>
> The control grid and cathode are not connected in the 30S-1.

Not connected DC-wise, but for RF, there is virtually no signal 
potential between the grid and the cathode.
>
> G1 is essentially bypassed to ground. It receives a small fraction of
> the *anode* voltage as negative feedback, but it isn't connected to the
> cathode at all.
>
Agreed, and the driving signal is applied to the cathode, so the 30S-1 
is  Class AB1 cathode-driven.
>
> -- 
> 73 from Ian G/GM3SEK
> http://www.ifwtech.co.uk/g3sek
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org