That would be the echo of me banging my head on the wall... Now that the thing is in resonance, it works brilliantly with my subharmonic direct conversion receiver. Grggrrrrrr, I took it for granted for several weeks, that the dimensions of the loop were ok, and put all efforts to the 6:1 balun... Now that I think of it more clearly (don't you ask me why this didn't happen earlier, you don't wanna know!), it is sort of clear, I am not using 300Ohms window line as I used for the 40m DCTL, but rather EUROPEAN (!!!!) TV-twin, which is 240Ohms (I believe), and thus, also has got a different capacitance per length.
Bonk bonk bonk ...
Bonk bonk bonk!!!!
But now, it seems, I am onto something. Receiving the mystery station from JN44AE now, 2037z.
The DCTL finally usable for QRSS? I hope so, I intended to use this sort of aerial for future journeys, to put signal in the air, or maybe receive occasionally...