Topband: Sunspots increase gud/bad for 160m?

[Carl K9LA]

Sam,

Those of us who have been in Amateur Radio for many years (the polite 
way of saying many of us are old) have grown up under the axiom that 
160m is only good at solar minimum. But over the years I've seen more 
and more evidence (in the form of a better fundamental understanding of 
the ionosphere and in the form of log data) that indicates this is not 
necessarily true. The solar min concept could simply be a 
self-fulfilling prophecy - it's easier for the majority to be on 15m and 
10m at solar max with S9-plus signals than struggling on 160m with weak 
signals at the noise level.

A great example of DX opportunities at solar max is W8JI's log data from 
the peak of Cycle 23. Tom had over 5000 DX QSOs outside of North America 
for the three year period when the smoothed sunspot number was greater 
than 100, and this included over 200 countries and all 40 zones. Sure, 
he has an exceptional station, but I believe the most important issue 
was being there every day regardless of the high sunspot number.

Another example is the recent work of NM7M. He has shown log data 
indicating that longer distance QSOs can be made at solar max, and this 
is believed to be due the effect of cosmic rays on the electron density 
valley above the E region peak in the nighttime ionosphere. That's an 
interesting observation that appears to turn our old beliefs upside down.

In general I believe solar min is best for paths through the auroral 
zone and across the polar cap. IV3PRK's data to North America tends to 
confirm this. But there are exceptions to this, as many have noted on 
this reflector. The problem is the lower ionosphere greatly influences 
160m propagation, but we don't have a direct parameter that ties the 
lower ionosphere to 160m propagation. And I doubt that we will have one 
in the foreseeable future.

So to answer your question, I think there's DX to be worked on 160m 
regardless of the sunspot number. Yes, there will be more disturbances 
to propagation at solar max that could render 160m (and the other bands) 
unusable for days at a time. But those disturbances aren't necessarily 
bad, either - weird propagation can and does happen.

Carl K9LA