Calculations for the Anode Circuit  
The parallel plate output circuit design is directly from the 144 MHz amplifier design
notes from the 1999 ARRL Handbook (page 13.23). Here are the design calculations:
Now, calculate the circuit assuming the tube output capacitance plus the stray capacitance
of the enclosure results in a capacitance of 24 ohms. Assume an operating tune capacitance
of 2 pF, for a total plate output capacitance of 26 pF:
The circuit Q may be approximated with the ratio of the plate load and the reactance:
This design is based on using a capacitor in series to match the tube impedance to the 50 ohm coax impedance. The value of this capacitor cannot be calculated directly. However, it is straightforward to calculate the parallel equivalent of the load capacitor using the equation:
The actual value of this parallel equivalent may be calculated from the following equation:
Once the reactance of the parallel equivalent of the load capacitance is known, it is possible to directly calculate the inductance needed if this capacitor were in series:
The reactance of the plate load capacitor (now in series) may now be converted to its capacitance value:
We must now calculate the value of inductance necessary to form the parallel resonant circuit. We want this inductance to resonate with the value of the parallel capacitance at the design center frequency of 144 MHz. Recall that we had 26 pF of tune + stray capacitance (24 pF tube output + stray capacitance, plus 2 pF of tune capacitance). We now also have the parallel value of the load capacitance that is also in parallel with the tube and tune capacitance: This translates to a capacitive reactance of:
Note that this capacitive reactance is between the plate output line and ground.
Each resonator pipe/doorknob combination needs to total 76.2 ohms. Therefore, each resonator pipes needs to be 76.2 + 5.5 = 81.7 ohms of inductive reactance. Each one of these inductor pipes then needs to be:
Now, to summarize the values, recall that we used a tune capacitance value of 2 pF. We then calculated a series value for the load capacitor of 3 pF, and a value for each of the resonator pipes of 0.09 uH. The circuit design is complete.
or plates 2.125" x 2.125" square. The same equation yields the size of the plate load capacitor:
or plates roughly 2.5" x 2.5" square. The lengths of the resonator pipes can be calculated using an equation from the ARRL Handbook: where:
Z_{0} = the characteristic impedance of the resonator configuration
This characteristic impedance is approximately 130 ohms for a 1.125" pipe centered
within the square enclosures at the sides of the amplifier chassis. Solving this
equation for l results in a resonator length of 32 degrees,
or 7.375”.
