Since teatime I have been back on 472kHz (630m) WSPR. As an experiment, I ran the shack PC from its internal battery so the noise on RX dropped 7 S points. What I forgot was that the PC sleeps on batteries!
Tomorrow, I'll change the settings so the PC does not sleep ever when on batteries. On batteries the PC should last an evening and maybe a whole night session. I have since returned to the external SMPSU but this means only the strongest stations are spotted on MF. So far this evening the best DX on TX (5mW ERP) is PA0RDT (243km) who has spotted me a few times.