Pi-matching network calculator

This calculator is designed to calculate a real Pi-matching circuit of the tube power amplifier of the transmitter or the PI-filter in another words. It is assumed that the idle Q-factor of C1 and C2 is much higher than that of the L. It is true for most capacitors. Increasing the loaded Q-factor of the Pi-circuit Q_p, increases harmonic suppression and condensers capacitance (important for high-power electron tubes), but reduces efficiency.

For the output Pi-network of the amplifier:
R1 ≈ Ea / (2.1 • Ia)
(where Ea is a constant voltage and Ia is a direct current of the anode), or
R1 ≈ (0.9Ea) 2 / 2P
(where P is the input power of the matching circuit).

In case of input Pi-matching circuit for the power amplifier with a common grid
R2 ≈ 1 / S
(where S is the gain slope of the electron tube).

To estimate the design requirements for the circuit parts, effective currents in the coil and in the capacitors are calculated. For capacitors, peak voltage and reactive power are also calculated. The peek voltage can increase 2..3 times (depending on the antenna SWR) compared with the exact matching case.

Pi-matching network calculator

Put your own values F, Q_L, Q_P  (for tubes  10...20,  for transistors 2...10), Р_in, R1, R2.

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Working frequency F [MHz]	Q-factor of the coil; QL	Q-factor of the Pi-network; QP	Input power Рin [W]

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L: [µH]

Source impedance R1 [Ohm]

Load impedance R2 [Ohm]

C1: [pF]

C2: [pF]

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Parameters of the capacitors

	Reactive Power Pr [VA]	Peek Voltage Umax [V]]	Peek Current Imax [A]
С1
С2

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Peek current in the L [А]:		Output power Рout [W]:
Losses in the L [W]:		Efficiency factor %:

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Original calculator by DL2KQ is the prototype of this calculator.

The calculator has been developed by DL2KQ collaborating with UA3DA UA3SDE and other.