[Amps] Re: GU-84b: Drive power required for full power output ?

[R.Measures]

>Hi Peter, Rich, & all the others on this list,
>
>thx for replies. Having expose myself as mostly new to tubes and such, I
>see that the GU-84b allows for -150V on the grid.
>
>Given a 50 Ohm input circuit about 100V peak will be produced by 100W
>drive power.
>
>This would require to bias the grid at about -100V which is within
>limits of tube parameters. 
>
>What would be the consequences out of this? Rich, you mentioned a
>typical value of about -80V for the grid bias. 

•  -80v looks like the needed bias potential required to produce a 
reasonable ZSAC.  Thus, +80v of peak drive would be needed to produce a 
peak 0v on the grid.  

>Sorry, I still do not
>have any suitable datasheet (and found none on WWW too)...
>
>So my parameters for the GU-84b are:
>
>Ua  = 3000V  (Anode)
>Ug1 = -100V  (Grid)

•  -100v on the grid does not produce enough ZSAC.  

>Ug2 =  375V  (Screen)
>
>What would be the resulting values for 
>
>Ia 
>Ig2 
>
>???
>
>Thx for all the assistance so far!
>
ur welcome, Frank
>
>
>
>  
>
>
>On Fri, 2004-03-26 at 17:06, R.Measures wrote:
>> >In einer eMail vom Do, 25. Mˆ§rz 2004 18:21 MEZ schreibt 
>> >frank_goenninger at t-online.de (Frank Goenninger):
>> >
>> >>I initially intended to ask if about 1A of input current will be enough
>> >>to really get reasonable power output?
>> >>
>> >>This comes from a simple calc from Pout of the TRX, which is about 100W
>> >>producing about 1.4 A of current into 50 Ohms.
>> >>
>> >>Also, for this tube, what type of input circuit would you recommend when
>> >>trying to cover all bands up to 30MHz ?
>> >
>> >Hi Frank,
>> >
>> >Since this is a tetrode it will be run without grid current, 
>> >the driver does not need to deliver current, just voltage.
>> >Typically the grid is loaded with a 50 Ohm dummyload, into
>> >which drive voltage developes without tuned circuits.
>> >For the higher bands you probably have to compensate the high
>> >input capacity with a small coil in parallel.
>> >I guess you will need not more then 25W drive for full throttle.
>> >
>> ’Ä¢  My guess is that with a 50-ohm termination, somewhat more than 25w 
>> will be needed to drive the grid up to the 0v point.  The grid potential 
>> is typically -80vdc.   64w is needed to produce 80v-pk across 50-ohms.  
>> 
>> cheers, Peter
>> 
>> 
>
>