[Amps] VHF amplifier input network

[Han Higasa]

Thank you very much for the reply Ian.

I realized that the network

input - VC1 - L1 - VC2 - L2 - Cin//R

can be written as

input - C1 - L1 - L2 - C2+C3 - L3 - Cin - R

where C1 and L1 is a series resonance circuit,
and remaining circuit L2 - C2 + C3 + L3 - Cin comprises
a L-pi circuit.

Assuming C1+L1 is resonating to the center frequency,
and using the equations introduced in the ARRL handbook
I obtained these parameters for different intermediate
impedance (Rm) from 100 ohm to 250 ohm, with specific 
value of Cin and R. Where R in ohms, L in uH and C in pF.  

Rm     L2 C2+C3  L3    R   Qo
250  .318   55     .350   50  5.3
200  .275   64     .317   50  4.7
150  .224   70     .275   50  4.0
100  .151   76     .222   50  3.1

The calculation process needs to solve a second-order 
equation for Qopi from R, Rm and XCin. 
Then Q2, Qo and QL are delivered, and then
XL2, XL3, XC2 and XC3 can be calculated.

As Ian have mentioned I think the series resonance
circuit C1+L1 adds a flexibility by an ability to 
compensate a range of +j or -j in series of the network.

I can now calculate any parameters in this type of input
networks, and will prepare for next summer solstice.

Thanks again, 
and have a good Christmas and happy new year.

de Han JE1BMJ