[Amps] Pi network tuning

[R L Measures]

On Jul 23, 2006, at 7:10 PM, Tom W8JI wrote:

>> Please try this question on for size.  With the pi-network
>> built, and the tubes in the sockets and AC coupled to the
>> pi-network, is it possible to determine that the
>> pi-network values are correct by using a Grid Dip Meter to
>> determine resonance of the network?  I have a 50 Ohm
>> resistor hanging across the output capacitor.
>
> You won't know the impedance transformation, just resonance.

IME, resonance in a low-pass Pi-type Z-transforming network with a Q  
of 10 is typically around 10% lower than the operating frequency.
>
> The normal procedure is to terminate the anode to ground
> with the expected tube operating load impedance and check
> for 50 ohms at the output port with a low power SWR
> measurement device. You would also have to know at least one
> component value reasonably close and not touch that
> component to verify you are close to planned loaded Q.
>
> 73 Tom
>
>
>
>
>
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R L MEASURES, AG6K. 805-386-3734
r at somis.org