I think I only ever worked on 25 Megs once, and that was to a Scandinavian Station who favoured that band back in the day. For sure the high end of the HF spectrum was often greatly at the mercy of an active Sun.
But then the entire HF spectrum is at the mercy of Ra the Sun God in a bad mood. (I'm not in anyway religious, far from it .. but if I had to have a god to worship, old Sol would be a definite contender, very big, very powerful, and very .. very necessary to our existence. Godlike in anybody's book.)
