I have measured the impedance of the LC tank circuit which I referred on my last entry.
The configuration of the circuit is exactly the same as that time.
In order to observe the impedance, by using Koji's technique I injected a RF signal into the output of the resonant circuit.
In addition I left the input opened, therefore the measured impedance does not include the effect of the transformer.
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The measured impedance is attached below; "LCtank_impedance.png"
The peak around 50MHz is the main resonance and it has impedance of ~1500 [Ohm], which should go to infinity in the ideal case (no losses).
In fact the impedance looked from the input of the circuit gets reduced by 1/n^2, where "n" is the turn ratio of the transformer.
By putting the n=4, the input impedance of the circuit should be 93 [Ohm]. This is a moderate value we can easily perform impedance-matching by some technique.
I also fitted the data with a standard model of equivalent circuit (see attachment 2).
In the figure.2 red component and red letter represents the design. All the other black stuff are parasites.
But right now I have no idea the fitted value is reasonable or not.
For the next I should check the input impedance again by the direct way; putting the signal into the input.