[AMPS] MLA2500 and screen voltage for 4CX800.

Tom Rauch W8JI@contesting.com
Tue, 10 Apr 2001 20:58:53 -0400



> Hi Douglas this is a very bad idea. The IMD performance of any tetrode
> is dependant on good screen voltage regulation. The dynamic regulation 


That 's true.

> of the plate supply is pretty bad and this obviously causes problems
> with screen regulation if a string of zeners are used. 

Why? There is no reason it should cause problems if you wrap 
around the zeners with few transistors.
 
The series resistance of a string of zeners might be too large 
compared to the dynamic resistance of the screen, but if you have 
enough voltage feeding the shunt regulator (at least twice the 
screen voltage under full load) to properly current limit the screen 
the zeners won't waddle around enough to hurt. 

Just don't use zeners as the shunting device. Use some transistors 
so the current gain lowers the shunt impedance. That way you can 
use low power zeners, and regulation is good.





   




John Nelson
> GW4FRX wrote some excellent articles on this in the 80s.John frequents
> this forum so he may wish to comment.Meanwhile try this link for a
> solution http://www.ifwtech.com/g3sek/boards/tetrode/tetrode-1.htm and
> some background info.
> 
> Regards
> 
> Conrad Farlow G0RUZ
> 
> 
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73, Tom W8JI
W8JI@contesting.com 

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