Did some additional soldering on the 600m QRP TX, which is now foreseen with a BNC antenna socket. Hooked up the Plumbtenna (matching&coupling details) and just went for it.
The first tests, once again, were done indoors, from the ground floor.
Lots of plasma TV lines. It seems clear that the Plumbtenna actually radiates, at least a little bit. The HF3's AGC is clearly pulled (ant: Octoplumb, 2 stories higher). I did a little keying, nothing of significance though.
The spectrum indicate a VFO range from just below 501kHz to 503.2kHz. Fingers crossed that this will fall into the range (hopefully) to be assigned to radio amateur at the WRC12.