Not many people are very familiar with solar weather and how it affects us down here on Earth. For the most part, the sun is simply in the sky for a potion of the day, varying due to the current season and one’s location on Earth. We all know that the sun is important for the chemical processes of life, such as photosynthesis. Those with certain vitamin deficiencies are aware of how the sun provides them important vitamins for their body’s natural processes.
In the technology community, knowledge of solar weather can be sparse. For a programmer, the sun is merely a sign of when to work. When the sun sets, it’s time to order a pizza and crack open a can of Monster. For those interested in wireless communications, though, solar weather knowledge comes in handy. After hanging out with some maker communities, it’s amazing how many people are unaware of how the sun’s predictable solar cycles can affect our wireless signals.
That’s right. The sun operates on a fairly predictable cycle, called the sunspot cycle, which was first observed by Samuel Heinrich Schwabe. Rudolf Wolf, impressed by Schwabe, gathered sunspot data and used it to calculate the length of the sunspot cycle: roughly 11.1 years.
The cycle can be broken down into two simple blocks of time: a block of time with high numbers of sunspots followed by a block of time with low numbers of sunspots. In more recent years, scientists have discovered that the strength of these sunspots is related to the time in the cycle. During a solar maximum (period of time with a high number of sunspots), Coronal Mass Ejections (CMEs) are more common and powerful.
So, what does this mean for Earth? Well, CMEs have been known to knock out power grids for short periods of time, such as the Geomagnetic storm of March 1989, which caused a blackout in Quebec during Solar Cycle 22. These days, solar weather is monitored to migrate possible damage caused by these CMEs.
Outside of blackout events, the sun’s cycle plays a major role in how our wireless communications propagate throughout the atmosphere. Generally, during solar highs, radio waves propagate easier through the Earth’s atmosphere. This means that we can send messages from point A to point B with less power. Inversely, signals have a harder time propagating during solar lows.
Why is this of interest to the makers and anyone who studies wireless communications? Right now we are in Solar Cycle 24, on the beginning slope of solar minimum. This means that our signals won’t be able to go as far as in past years.
Every set of frequencies is different. Each has their own “personality.” A good example would be the Amateur Radio frequencies. The HF bands (frequencies between 3 MHz and 30 MHz) have properties that allow for world wide communications. Even within the HF band, frequencies have their own characteristics. Right now, the 40-meter band (7.025 MHz to 7.3 MHz) has seen pretty good conditions, regardless of the time of day (conditions on frequencies will also vary depending on the time of day.) The band has great long distance communication properties. Now, compare it to 10-meter band (28.0 MHz to 29.7 MHz) which is “closed” most of the time and can be difficult to work with at times. This means that most any signal put on the 10-meter band will have a much smaller range than on the 40-meter band.
The study of solar cycles and the propagation of radio waves is an interesting area of study. Anyone can get involved, too. Everyone right now probably has a radio within reach: a cellphone. Over a period of time, notice how your cellular signal changes. A solar maximum nets you the strongest cellular signal, while a solar minimum gives you the weakest cellular signal. Those interested in trying this experiment should also know about the characteristics specific to the frequency range of choice. For example, cellphones use frequencies anywhere from 700 MHz to 1700 MHz.
If you wish to see things in action with different frequency sets, look into getting an SDR dongle that can hook up to a tablet or phone. Most SDRs will cover up to 2.4 GHz.
Another way to see things in action is by going to the WSPRnet website. The site offers back logs of previous months and years using CSV files that can be loaded into database. It can also interact with maps, showing rough locations of where packets of data are being sent from and who is picking them up. By using WSPRNet, not only can you see how the solar cycle affects radio wave propagation, but you can also see how day/night and time of year has an affect on signals.