[North Carolina Prepper] did just that, creating his own trombone-style variable capacitor by stretching some aluminium beverage cans. The requirement was for a 26 pF to 472 pF capactitor ...

But the most fascinating bit of any old radio was connected to the tuning knob: the big variable capacitor with its interdigitating ... can be tuned between about 7 and 15 pF.