I’ve seen a lot of circuits with tubes at low voltage ( max 20V ), so I wanted to experiment with one too,… and what could be more fun to play with than a radio.
I started from a short-wave radio schematic with an ECL82, in which I replaced the ECL82 with a ECC81, which I knew could work at low voltage, and did a little tweaking with the resistors, and coils.
L1 = 4 turns, L2 = ~40 turns, L3 = 4turns, in this order on a ferrite stick. ( the fun part is to play with these coils and the variable capacitor, until you hear something ).
Note, that all the values are not strict, tweak them as you see fit.
I’ve also had great results leaving aside L1, and connect the antenna by a 100pF capacitor directly in L2.