I posted a small windows program in alt.binaries.schematics.electronic that some here may find useful.
The subject line to look for is "Paralel resonant circuit tuning range calculator program. -
TuningRangeCalc.zip (0/1)".
As the name implies it calculates and displays the resulting capacitance range and resonant frequency range
for a parallel resonant circuit using a main variable capacitor along with padder and trimmer capacitors. The
values for the parts are set with a set of slider controls and the results are displayed as the sliders are
moved.

Mike

"The scientist is possessed by the sense of universal
causation...His religious feeling takes the form of
rapturous amazement at the harmony of natural law,
which reveals the intelligence of such superiority
that, compared with it, systematic thinking and acting
of human beings is an utterly insignificant reflection."
Albert Einstein (theoretical physicist)