On Jun 11, 2021, at 2:40 AM, ON5KQ <ON5KQ@...> wrote:

Jim,
on 20m (and the higher bands) usually I hear the locals (100km distance) best, when both antennas are in the same direction (back-scatter)
So in the evening in 20m CW or SSB if stations put their beams to Northamerica, I would hear them best with the beam to Northamerica too. Although the many Germans heard like this are all in the back of the antenna...

So, I think the usually not very directive Wspr-wire antennas (both TX and RX, compared to a Yagi beam antenna) will work in the same way: Backscatter signals are usually stronger than direct ground wave propagation.

Ulli