Re: [Amps] Passive grid stability calculation for a tetrode?

["Carl" <km1h@jeremy.mv.com>]

About 300V PEAK

Carl
KM1H


----- Original Message ----- 
From: <donroden@hiwaay.net>
To: "Amps" <amps@contesting.com>
Sent: Friday, November 15, 2013 9:44 AM
Subject: Re: [Amps] Passive grid stability calculation for a tetrode?


> How much grid voltage swing for AB1 ?
> ( how many watts into a 50 ohm load )
>
> Don W4DNR
>
>
> Quoting Carl <km1h@jeremy.mv.com>:
>
> > Even CBers can build stable grid driven 4X5's!  It is a very hard  
> > tube to make oscillate.
> > The SK300A socket requires good screen bypassing for RF.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message ----- From: "peter chadwick" <g8on@fsmail.net>
> > To: "Markku Oksanen" <ww1c@outlook.com>; "Amps" <amps@contesting.com>
> > Sent: Friday, November 15, 2013 5:44 AM
> > Subject: Re: [Amps] Passive grid stability calculation for a tetrode?
> >
> >
> > > Markku,
> > >
> > > It may be shown that (i.e. as the books say, it is left as an  
> > > exercise for the reader!) if you have H<2 as a result of solving  
> > > the equation H=gwCpgRpRg  where g is the mutual conductance, w = 2  
> > > times pi times frequency, Cpg is the pate - grid capacitance, Rp is  
> > > the plate load resistance and Rg is the grid resistance, the stage  
> > > is stable. Arguably Rp should be the plate load resistance in  
> > > parallel with AC plate resistance of the tube, but sticking to the  
> > > load resistance gives a bit more stability.
> > > vy 73
> > >
> > >
> > > Peter G3RZP
> > >
> > >
> > > ========================================
> > > Message Received: Nov 15 2013, 07:32 AM
> > > From: "Markku Oksanen" <ww1c@outlook.com>
> > > To: "Amps" <amps@contesting.com>
> > > Cc:
> > > Subject: [Amps] Passive grid stability calculation for a tetrode?
> > >
> > > All
> > > I am back on my 4CX5000 project and as it not done yet, I am still  
> > > contemplating the circuit to be used.Earlier this year I got solid  
> > > info from this reflector for GG operation and that look like a  
> > > pretty good solution.However, I was wondering about passive grid,  
> > > grid driven also.
> > > The question is:  How do a calculate the stability?  If I simply do  
> > > math for tube voltage gain I get something like 25.Then if I  
> > > calculate the feedback capacitive voltage divider, Grid to Cathode  
> > > 120 pf, Plate to Grid 0.7 pf, I get less than 0.01 for the ratio.  
> > > If the beast needs the voltage gain times feedback gain to be above  
> > > 1 to oscillate, to me it seems this tube is stable no matter what.   
> > > Where did I err if I did?
> > > Thanks!
> > > MarkkuWW1C
> > > _______________________________________________
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> > >
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> > >
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