Notice the fluttery character of his signal. On this day it wasn’t too bad and it wasn’t too hard to copy his signal, but on other occasions, signals that travel over the polar zone may be impossible to copy correctly. The K-index in Tromsø, which lies between Oslo (60 deg. N) and Spitzbergen (78 deg. N), at the time was 0.
[Image source: regjeringen.no]