This evening, I am re-trying my 15m baseline earth-electrode "antenna" on 474.2kHz WSPR (approx. 5mW ERP) but at the moment there is a distinct lack of in-range stations. I shall keep the system running until tomorrow to see who appears.
The next test may be WSPR at 8-9kHz earth-mode with the same antenna. I may persuade G6ALB to appear on VLF WSPR (3km + away). The match here needs better optimising at VLF. Presently the earth system looks more like 300ohms resistive at 474.2kHz - a lot higher than at the old QTH.