Prior to digital control of frequency and frequency selection wouldn't tuning the radio also involve delicately turning knobs that continuously vary the frequency just as is required in old home and car radio receivers? I imagine that would be loads of fun especially as the frequency you're trying to tune in to may have long periods of dead air. I've actually got a ziploc bad of crystals left over from the radios my club used to use back in the days before I started flying. I have no idea why I'm keeping them...