Inspired by the references below, this is my build of the design described by John Hunter on his website (Ref 1),
and Peter Parker in his youtube video's (Ref's 2 & 3).
Constructed from re-cycled componentry.
Circuit appears to be a Hartley type, oscillating grid-leak detector, with the point of oscillation controlled by the value of Anode voltage which is 12 volt max.
12V also heats the valve filament.
My efforts at construction of "regenerative" receivers in the past, although being successfull, needed a full 200~250 volt DC HT supply, messy "tickler" coil and variable "reaction" capacitor as part of their design.
Later efforts used variation of screen grid voltage to control oscillation point (pentode valve), although it was generally from a zener stabilised rail.
This circuit is deceptivley simple and had you told me, way back then; that 12 Volt would be sufficient Anode voltage, it would be like saying that water can run uphill !!

Ref 1: http://cool386.tripod.com/kits/ace.html

Ref 2: http://www.youtube.com/watch?v=orSlJ9oJ3d0&feature=related

Ref 3: http://www.youtube.com/watch?v=9O6qUY7X4VA