Thank you Martin. I didn't consider the amplifiers input inductance. Now my math works out quite well.
For the LZ1AQ when using the 2 (effectively in series) 0.3uH FM filter inductors and 2 (effectively in series) FM filter 100pF capacitors:
Then,? 3uH loop inductance in parallel with 0.6uH = 0.5 uH. When placed in parallel with an estimated 5pF loop capacitance + (100//100) 50pF FM filter capacitance + estimated 5pF circuit capacitance? = 60pF, the resonance comes out to 29MHz.
For the Wellgood input inductance would, I assume, largely depend?on leakage inductance of the input transformer. And since these are home-made their inductance could vary quite a bit. So actual testing would probably be the best way to determine the optimum input capacitors.
Do I have this right?
Tom
