[Amps] 4-400 Amp Help

[David C. Hallam]

Have you measured the RF voltage on the grid when you apply drive?

David
KW4DH

On 3/31/2011 1:57 PM, Rahul Sathe wrote:
> Hello Experts,
>
> I just finished building a QB4-1100 / 4-400 Grid Driven amp. with
> following configuration..
>
> 1 X QB4-1100
> 450 V DC Screen
> -150 VDC on CGird, switched / keyed to ~ -50V DC for idle current of 80mA
> 2800 VDC on Anode which drops to 2200 on key.
> Input is applied to CG using a 2 turn: 6 turn air core transformer
> (1/2 inch dia, 1 inch spacing) with bias feed through 6 turn winding.
> The 6 turn winding is resonated with a 30 pf variable cap.
>
> With ~ 5 W input from my TS130 I get ~ 120 mA plate current giving ~
> 130 W output. if I increase the drive the output does not increase
> beyond 130, and the plate current stays ~ 120 to 130 mA.  Where am i
> going wrong?
>
> The tube can deliver 400mA in case I reduce the bias on grid.... but
> not with the drive?
>
> can someone  help?
>
> Regards /// VU3RAZ
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