I'd like to control the frequency of a low frequency sine oscillator with air core variable capacitors. Is there a type of sine oscillator circuit that could be controlled by such low value capacitors at very low frequencies? Big resistors? capacitance multipliers? I haven't figured out the values of the air capacitors in the old radios i got. One radio is an atwater kent model 55c and it has a triple air core. The other radio is much smaller and has two sections with different numbers and sizes of plates. I assume they're all under 500p. Can I somehow do this?