Thanks for that tip also, Ken. I thought the high meg grid resistor would cause blocking, as in superregeneration.

I had decades ago a Knight Kit Space Spanner regen receiver. Something happened inside the 12AT7 det tube. Whereas before in straight regen mode, it could perfectly separate stations 10 kHz apart in the then crowded 49 meter band, in superrrgen mode the selectivity was more like 100 kHz, there was a weird "springy" sound, and it was so MUCH louder on the selected station.

I have a kit radio regen for the MWBC band which has a 1000 pF grid cap. Maybe that was to simplify the parts count for beginners, but that seems to me a real mistake, and i want to try it with the more usual value.