Hello Bill and Gerald,
it is also possible that the load C is at a low value. In that case you need
more C on the plate. Often, only C plate can be reached from the front,
while C load is inside....a brass screw with locking nut or a "sliding"
construction.
If it is really necessary to increase the plate C, I would increase the
flapper size instead of getting to close to the anode. BTW: If you add a
piece of teflon sheet between the flapper and the anode, the capacitance
will increase....and also the safety!
Tom, DJ5RE
----- Original Message -----
From: <TexasRF@aol.com>
To: <billdz.geo@yahoo.com>; <amps@contesting.com>
Sent: Friday, June 11, 2010 3:25 AM
Subject: Re: [Amps] GS-35b 2 meter amp - plate capacitor spacing from tube?
> 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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