Thanks to all who replied. I was able to extend the plunger, and output
increased to 850 watts, with 50 watts drive. And I was able to find a dip.
The only thing that seems odd is that the plate current meter is still reading
just 230 ma. That can't be right. With plate voltage of 3300v, there has to
be about 500 ma to get 850 watts output.
73, Bill
> > Bill, with plate current that low, the plate load
> impedance is pretty high.
> > To match a higher impedance requires less coupling C.
> Less coupling C
> > means you need more tune C to keep the plate
> circuit in resonance.
> >
> > If you increase the drive level, the plate current
> will rise and the plate
> > load impedance will be lowered which will call for an
> increase in coupling
> > C and a reduction in tune C.
> >
> > If you are unable to increase the drive power, then
> yes, you need to change
> > the tune C plunger to allow more tune C to be
> available.
> >
> > 73,
> > Gerald K5GW
> >
> >
> >
> >
> > In a message dated 6/10/2010 3:54:09 P.M. Central
> Daylight Time,
> > billdz.geo@yahoo.com
> writes:
> >
> > Any Russian tube experts on this board?
> >
> > Picked up a homebrew GS-35B 2 meter amp, seems
> to be working OK, about 650
> > watts out with 50 watts drive from my
> FT-847. The anode is tuned with a
> > piece of copper that is pushed closer to the
> tube or further away by a
> > plunger controlled by a knob on the front
> panel. Power was still going up when
> > the plunger reached its maximum push on the
> copper, which leaves the copper
> > about 3/4" (20mm) from the tube. Do you
> think perhaps the plunger needs
> > to be extended to get the copper closer to the
> tube for best output? Plate
> > voltage is 3300v, plate current only about .23
> amps.
> >
> > 73, Bill NZ5N/OM9ACA
> >
> >
> >
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>
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