Topband: DX condx better higher in the band?

[Tim Shoppa]

I could not help notice, that several prominent well-known DX'ers were
CQ'ing up well above 1850kc over the weekend.

One reason I'm sure was that the QRM was thinner up there, and the mix
certainly was tending towards more low-power Europeans than lower in the
band.

But I wonder if there is some magic corner frequency for topband
propagation, where sometimes getting across the pond is easier up there
than just 40kc lower?

Tim N3QE