The precision of 15m propagation

Well, although there have been recent upswings in the number of sunspots, the past few days have not been so hot on HF.

Still, undeterred, I have a go at CQing on 15m every day.  In fact, I first discovered the remarkable performance of a delta loop antenna, when I experimented with a 15m loop, way back in 2011.  As soon as I installed it, I was bringing in excellent DX, especially from the west.

This afternoon, the CQ resulted in a few PY stations responding.  Looking at PSK Reporter, it was amazing to see just how geographically limited the propagation on 15m was at this time, as the plot below shows:

Of course, an all-sea path to PY helps enormously, and that path is open quite regularly.  But it's not quite so common to see propagation so strictly limited to a very small area of PY.  Note also the very big range of received signal strengths at the same time, in the same area.  Strangely, the strongest signal comes from a station in the very built-up, and probably very RFI-infested area of Sao Paulo.