GU84b based amp ? tetrode boards for control.
OK so, working again on my amp, 2.3kv on plate, 350v (when ON) to G2 and
G1 has 65v. I have well over 1 amp available for plate current if
needed.
Used several tank calculators, Jim Hawkins, PI network v1.0, G4FGQ?s
calculator..whatever
Else I could find out there to do comparisons. Found out that the W4ZT
calculator was pretty close.
I used about 940ohm for my plate impedance, I can run 1, 1.5, 2kw
calculations but I started with 1.8kw. assumed that the tank Q
Was 12 ? 12.5, Rp made 968 ohms.
I set this all up with my Boonton inductance meter, cap meter on the C1
and C2 (all out of circuit) and assembled it. I have done this
Several times. I used my MFJ analyzer and setup the circuit, tube in
place connected just swept the tank and looked OK.
Power up 
3.8mhz,
C1 ? variable to 0 to 500pf, vacuum cap. Set as needed
C2 ? variable to 1000pf vacuum cap PLUS THREE 470pf Russian door knob
caps. 1400 2400pf total available. (I checked these with cap meter all
ok)
Set that as needed.
Inductance pretty close to 5uh a little below, I had to short one coil
section to get it there as I am using the whole coil I wound
Out of ¼ copper tube ? wound over a Krylon spray can.
Now then?
Problem I am CONSTANTLY having is to have tons of C2, like the vacuum
cap has no more, seems like both 80m (and 40m
I tapped the coil there for 40 also). I can pull easily 1.5kw out on
both these bands but its with the vacuum cap out all the way (max
capacitance) and
When I am turning the cap in (decrease pf) the power decreases. And I do
see the grid current start to drop also.
I switched from a 600pf to 1000pf vacuum cap to see what that would do
and it still wanted more. I have checked the total C2 pf readings they
look OK.
What?s wrong with this picture??
Now what direction should I go in here with this? Assume different Rp
and see what I can poke and hope with?
Thanks ?Chuck ~ka1mwp
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