> question: could somebody (did they at the time) write a program for the apple > ][ to create such a diskette? The apple drive can do half track stepping, and > IIRC the signal is written strictly by a timing loop in the program
Not really. Merely half-stepping a drive wouldn't be accurate enough, plus you need to be able to drive not-data waveforms into the heads. This is an accomplishable thing nowadays, but it's not something you can do with normal hardware. If I were doing it, I'd replace the stepper in a drive with a servo positioner and use a packaged digital micrometer to determine absolute position. The spindle bearings would probably have to be upgraded, but that's no big deal. We designed, maintained, and calibrated inspection gauges using the same basic operating principle for automated compliance inspection tools at a previous job, nowadays there's no "inventing" involved for problems like this, just expensive industrial Lego. One would then drive the heads with an external power amplifier and a triggerable arbitrary function generator. Index alignment would be the only "needs calibrated from an extant AAD" element, as that would be your trigger for the AFG. (Un?)Fortunately AADs are still cheap and plentiful enough that the above exercise is not the cost effective route...so we keep vintage AADs to get out work done. Thanks, Jonathan
