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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