In case it has a parallel resonance, then the pancake coil may be connected directly between the TG  SA 'center' pins where the optional resistance is shown in Verpies drawing. And a dip should appear at the parallel resonant frequency while a peak should manifest at a series resonant frequency. Do you agree?
Itsu has already tried connecting the pancake coil between the TG  SA 'center' pins and he did get at dip, see here. That dip was noisy because in such setup, the pancake coil, which behaves as a parallel LC circuit, had the highest impedance and kept the signal amplitude low at the SA's input. This is to be expected with such connection. The alternate connection is designed to yield the maximum amplitude at resonance. To get a peak (not dip) with a parallel LC circuit one can also measure the magnitude of its impedance at various frequencies (having an impedance bridge or VNA helps). Impedance will be highest at the resonance. This is illustrated on the two plots of my coil below. The first one illustrates the magnitude of the impedance of the coil vs.frequency. Notice that near the peak the impedance reaches ~7kΩ ! The second one illustrates only the reactance of the coil vs frequency. Reactance is the imaginary component of impedance and is supposed to be ZERO at resonance (because at resonance, the inductive reactance and capacitive reactance cancel each other). ...and they do that at 6.3MHz. The second plot also proves that the pancake coil behaves as an LC circuit up to 8MHz (anything above the 0 represents inductive reactance and below  capacitive reactance)
« Last Edit: 20200629, 09:38:07 by verpies »
