Ya know,
I remember the original article in QST about this 6AQ5 regen set. I
still have the magazines but can't remember the exact year.

I recall in the first paragraph, the author stated that, "some eyebrows
may be raised at using a beam audio tube for a detector". And as I
recall, he explained why. He just tried a number of different tubes for
smoothness of operation, and the 6AQ5 won.

I built my first two tube blooper in 1954 and used a 6J7G regen
detector and a 6C5GT one step AF amplifier driving a pair of Trimm 2000
ohm headphones.

It worked great and covered 80 and 40 meters.

John