The requirement was for a 26 pF to 472 pF capactitor, for a radio transmitting from 7 MHz to 30MHz. The concept was to use two beverage cans, one sliding inside the other, as a capacitor, with an ...

Make the coils variable if you need trimming, instead of having trimmer capacitors in parallel. Varactors have taken over for many uses. But they won’t handle power.

Binary selectable variable capacitor increases tuning and matching design options. ... Overall capacitance ranges from 0.7 to 4.6 pF in 131-femtofarad (fF) steps.