Hi Reading the article by Sir Douglas Hall, he mentions making an adjustment to keep the positive feedback below the point of oscillation. This sure sounds like regenerative to me. Regenerative feedback was used quite often to increase the effective Q of circuits to increase selectivity. The article of May 1976 seems to indicate that this is how this circuit works. This makes sense. There are many, many ways to introduce regenerative feedback. One of the early ones was to place a variable coil in the plate circuit that was not coupled to the tuned input. The circuit worked by the parasitic capacitance of the triodes grid to plate. This can be done with a transistor as well. I remember when I was a kid, I had one of those 2 transistor reflex receivers made by GE ( wish I still had it ). I modified it to be regenerative and was able to greatly extend both range and selectivity. At night, I pulled in stations across the US. Dwight