I am testing on your LF WSPR2 signals a new RX
It is a small home made single turn vertical
diamon shape loop (1.25 meter long each side) up 6 meters high with an azimuth
rotor. It is not tuned, only a back resistive load. So, it has a monodirectional
lobe. It is optimised for a maximum F/B ratio at 40° wave angle for night use,
but you can see that on day ground wave conditions the F/B is not too bad also :
36 dB on your signal. HI !
The advantages of this solution over a classic
tuned loop is that the closes metal structures or trees has very little effect
on the antenna, and also it gives a good directional lobe from 0 to 60° site.
Remember that a tuned loop is a very poor RX antenna because it has no F/B
attenuation and a very poor F/S ratio except for ground wave
73 de Andy.