Hi Tom,

I am researching how to calculate the plate resistance of the 813's. There is enough mixed messages out there that I have no found a clear answer. Maybe it is as simple as the plate voltage/current but then I have to make an assumption about the current....

Rich

Rich,

For operating points other than class C, the load impedance isn't the simple resistive calculation it is for Class C due to the dynamic impedance variation throughout the conduction cycle, even for Class A where the observed DC plate current is constant. The plate impedance is usually much less, for example, for Class AB single ended RF service, it is typically half the average resistive value. For Class A RF service, it can be about a third.

I'd go with about 4K for two 813's as the class AB linear load impedance for your pi-network calculations. If the actual impedance is a bit higher, this just means the Q of the tank will be higher which is fine.