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

[Frank Goenninger]

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. 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)
Ug2 =  375V  (Screen)

What would be the resulting values for 

Ia 
Ig2 

???

Thx for all the assistance so far!

73, Frank



  


On Fri, 2004-03-26 at 17:06, R.Measures wrote:
> >In einer eMail vom Do, 25. März 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.
> >
> •  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
> 
>