Having used my antenna once and having to resort to the tuner due to lack of patience and poor planning, I took the opportunity to set it up at home, trying to get low SWR in each band. I also made better radials.
The results surprised me! Mine is now a great field antenna. Easy to set up and use without a tuner.
I was less precise about it - cut 20m of wire into 6 radials and stuck ring connectors on the ends. I know that for 20m (and 40m with the loading coil) it needs to be almost fully extended so I start with that and adjust to suit and try to get a low SWR. It works well enough.
The length of the whip varies with location and the optimal length is never the same between different sites for me so for me there’s no point in checking it at home with the NanoVNA and trying to mark positions on the whip.
Mine has been consistent on wet and dry grass, hard packed ground and limestone, in Scotland and Florida.
Maybe because i have 8 radials, and I’ve always had room to fan them out equidistant.
This is what I have found also. I had marked the whip with a sharpie in the garden, but found it varies depending on the ground conditions on a summit. But that is also with 3 radials
Seemingly 3 isn’t a radial field, but 8 is. 