In my narrower, but wider, garden, I am still trying to work out the best layout for an earth-electrode antenna for 472kHz.
Today I started by trying to find out about the ground connections at the house end, measuring the resistance between various radiators and the mains ground to see which ones had a direct copper connection to a good ground. The answer is none! All the radiators seem to be connected with plastic pipes in the roof. The only direct "copper to ground" connections found in my water system were in the airing cupboard, the kitchen taps and the utility room taps.
The other tests (ongoing) are to a different remote ground further up the side of the garden, further from the shack but not further from the house. I am trying to see if this gives, effectively, a longer earth-electrode baseline between ground points.
So far this evening, with the (perhaps) slightly longer baseline, I am getting consistent reports from G6AVK (78km) but no-one else yet. As best I can judge, reports are very similar to those with the earlier grounding arrangements. PA3ABK is a very strong signal at -6dB S/N.