The combination L1/C1 does NOT resonate at the operating frequency. The two
components create a virtual inductance that becomes the series input arm of an
L network that cascades with a second L network which is comprised of L2 and
the tube input C.
C2 is basically the shunt C of the first L network. You might think of C2 as
the input C of a Pi network but this is not exactly correct. After all, a Pi
Network is actually a back to back pair of L networks.
73,
Gerald K5GW
In a message dated 12/19/2007 10:39:27 P.M. Central Standard Time,
higasa@plum.ocn.ne.jp writes:
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
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