Yeah Jim,
You tune a super-regen by simply going near it. :lol:
But I thought that besides not having an FM detector and relying on tuning to the side of an FM station to slope-detect it, its very high distortion was caused by it having a very narrow passband when oscillating. The Q of the tuned circuit must go through the roof when it is oscillating. Unlike other super-regen circuits that have a sensitivity control that is carefully adjusted to avoid oscillation, this circuit does, then stops by squegging, then starts and stops over and over. I wonder if its frequency sweeps a little as it gallops along.
It is amazing that this simple circuit does anything with its extremely low supply current. I might make one to see how easy it overloads from local stations since I have many.