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It Seems to Us: Where Are the Spots?

02/01/2010

By David Sumner, K1ZZ
ARRL Chief Executive Officer

If you're new to Amateur Radio and have not yet experienced a peak in the solar cycle, you may wonder why you should care about sunspots. The reason is that high sunspot numbers turn the higher HF bands -- and 6 meters, for that matter -- into worldwide DX bands by increasing ionization in the F region of the ionosphere. The details of this phenomenon are beyond the scope of an editorial; suffice it to say that ionospheric propagation is what makes the HF bands such a precious natural resource, worthy of protection against pollution from sources of radio noise such as power lines and other unintentional emitters.

The truth is, we know very little about the central body in our solar system. It's not a place we can visit! The Sun has been pumping away for billions of years, but the only systematic human observations of sunspots that we know of began in Galileo's time and the existence of a solar cycle was not recognized until the mid-19th century. It's a bit presumptuous to think that such a brief historical record provides a sound basis for predicting relatively short-term variations in solar activity.

As of mid-December 2009, according to the Space Weather Prediction Center at the National Oceanic and Atmospheric Administration the most recent update by the Solar Cycle 24 Prediction Panel was released on May 8 of that year. The consensus opinion of most (but not all) of the panel members was that a solar minimum had occurred in December 2008 and the next solar maximum was expected to occur in May 2013 with a maximum smoothed sunspot number of 90 -- low when compared to most cycles, but still enough to breathe a lot of life into the 15, 12 and 10 meter bands and to turn 20 and 17 meters back into nighttime DX bands. This prediction was for a peak occurring later than the previous prediction for Cycle 24, and with less likelihood that the maximum would significantly exceed 90.

However, since then the sunspot numbers have lagged behind expectations and as of November 2009 there was a significant gap between the observed monthly values and the predicted values. Smoothed monthly values are not available until several months after the fact, but it would take a dramatic spike in solar activity to get the numbers back on track to meet the panel's prediction. It will come as no surprise if their next prediction is scaled back even further.

Cycle 24 has been so much in need of a jump start, there has been some concern that we might be headed into another Maunder Minimum. This was a period between 1640 and 1710 during which very few sunspots were observed -- not for lack of trying, but because they weren't there. We don't know why this occurred or what the effects on radio wave propagation might have been, nor do we know whether it will happen again in our lifetimes. Indeed, until Cycle 24 got off to a slow start we didn't worry about it very much. For the entire history of radio communication there has always been a sunspot peak every 10 to 12 years. Some peaks were higher than others, notably the 1958 one for which most of us were born too late, but there has always been a nice peak so we've assumed there always would be.

If that holds true once again -- and as yet there's no reason to assume that it won't -- in the coming months we will see a gradual improvement in the usefulness of the higher HF bands. This will make operating more fun for more of us than ever; Cycle 24 will bring us the first peak for which every FCC-licensed radio amateur will have phone (limited to 28.3-

28.5 MHz SSB for Novices and Technicians), RTTY, data and CW privileges on 10 meters. Unlike the bands at the low-frequency end of the HF range, at its best 10 meters can provide worldwide communication even if your antenna possibilities are limited; even a mobile whip is pretty efficient here. Also, because 10 meters is much wider than the other HF bands there is plenty of elbow room in which to chat with new friends in other countries or on the other side of our own.

Nor should we continue to neglect the other bands that we've probably forsaken for the past few years. Thanks to the 1979 World Administrative Radio Conference there is less than 4 MHz between each of our HF bands; we can follow the maximum usable frequency (MUF) up and down with greater precision than our 1958 counterparts. General, Advanced and Amateur Extra licensees shouldn't overlook the 12 meter band at 24.89-24.99 MHz just because it's only 100 kHz wide. For a particular path the MUF reaches 25 MHz more often than 28 MHz, and the band is less crowded (no contests, for one thing). Next lower in frequency is 15 meters, a very nice band that we tend to take for granted -- although Old Timers will remember that there was no such ham band until 1952.

To sum up, despite the slow start to Cycle 24 we should enjoy steadily improving conditions on the higher HF bands over the next three or four years. As is often said here in Connecticut, if you don't like the weather just wait a while. The same can be said about HF propagation, although the wait may be a bit longer!



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