Sure, you tune the BFO and the main tuning in opposite directions at the
same time. Collins did that mechanically in the 75A4. The main tuning
PTO and BFO PTO were mounted on trunions connected together with a flat
belt (bronze) and calibrated to the same number of hz per degree, the
pass band tuning rotated their cases to get pass band tuning. This was
the first ever radio with pass band tuning, and probably still the
simplest and most reliable. Circa 1954.
73, Jerry, K0CQ
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