Solar Cycle 25: Using The Sun's Radiation for HAM Radio

According to NASA, we're now reaching the peak of Solar Cycle 25, meaning our Sun is launching radiation toward Earth at it's highest rate since around 2019. For most of us this doesn't mean much; the radiation is blocked out by Earth's atmosphere and magnetic field -sometimes, we get to see the aurora borealis (northern lights) as far south as the Midwest, as high solar radiation means more charged particles in the skies. But, for those of us involved in radio and telecommunications, the peak solar cycle can be an exciting event. Amateur radio clubs like the ARRL even make merchandise commemorating the event! So, it seems I got into HAM radio at the perfect time. 

Monitoring solar conditions for 10 meters

In my last article, I mentioned I wanted to expand beyond my FM (UHF and VHF) radio rig, which is perfect for transmitting clear voice radio signals about 30-40 miles in all directions reliably at all times. This reliability is why FM is the preferred mode for commercial radio these days, and why UHF and VHF are used by civil services, police, and emergency dispatchers. While other modes can broadcast farther, their signal strength may be unreliable during certain hours, or reception can worsen in certain areas. 

However HF radio, with short wave-heights, and longer wave-lengths -10, 40 and 80m etc, instead of 6, 2, and 70cm) can reach extremely far distances with the same or less power than UHF and VHF. One of the main factors impacting how far a radio wave can travel is the solar radiation in the atmosphere. Working on the 10 meter HF band, for example, is usually only possible during daylight hours, since waves on these frequencies rely on bouncing or scattering off of the Ionosphere's free electrons at about 100 to 500 miles above sea level. At night, without the sun's radiation, there are fewer electrons in the Ionosphere, but they gradually increase as the sun rises throughout the day. Typically, the increased layer of charged electrons during the day acts as a mirror or wall for 10 meter radio waves to bounce off of and propagate farther distances around the globe. At night, and during times of low solar radiation, the less-charged ionosphere absorbs these waves like a sponge, and prevents them from traveling far distances. 

Think of hitting a golf ball onto a hard plane, and watching it bounce farther and farther toward the pin, versus hitting into a muddy or water-logged area and seeing the ball stop dead as soon as it hits ground. Just like conditions on a golf course can impact the ball, conditions in the atmosphere can impact the course of a wave. So, while HF radio may be unreliable and unsuitable for critical communications, it's great for amateurs who want to communicate world-wide (when conditions allow), and experiment with different modes and propagation methods. 

While my Technician-class amateur license does not yet allow me to transmit on most of the HF bands, it does allow me to use a small portion of the 10 meter band (frequencies from 28 to 28.5 MHz). Some of those frequencies are restricted to digital modes, and others for single side-band (SSB) voice and continuous wave (CW)/Morse code. Since I don't know Morse code yet, I thought I'd try SSB with my new Yaesu FT-891 HF radio.

While FM uses an entire frequency bandwidth as it's carrier, single side-band transmissions use only one side of each frequency's bandwidth the upper (USB) or lower (LSB). While SSB transmissions can be more difficult to receive than FM, they allow for more transmitters to be heard within the same frequency range, and also propagate farther at lower power outputs. So, when communicating on SSB, it's important to be patient, listen very carefully, and also provide good signal reports back to whoever may be able to listen to you. For example, if you tell someone can hear you, but their response is fuzzy or faint, you'll want to communicate that very clearly so they can increase power, or move and adjust their antenna. 

It took some time, but I did get my very first SSB contact all the way across the pond in the United Kingdom (southern England to be exact)! This was very exciting, and quite gratifying, as I had only previously used SSB at my local radio club, with their pre-configured radios and antennas, and even then I was only able to get contacts in the continental US and Canada. This time, I used my own expertise, and with my very own radio and antenna, sent a signal bouncing off the Ionosphere. I was heard clearly on another continent. My mom always said I was cool!  

A report of radios receiving my signal

That said, it really is a great time to use the 10 meter band, so I'm lucky it's the one HF band available as a Technician-class licensee. As we near the peak of Solar Cycle 25, propagation on 10 meters is as good as it's been in years, and heightened solar activity allows propagation even at night and before dawn. At midday, it's actually possible for me to reach much father than Great Britain, even with a lower power output than I was using when I reached England. 

However, in the next 2-5 years, the solar cycle will begin to go into decline again, and the 10 meter band will become less-and-less reliable. Even during daylight hours it may be difficult to make SSB contacts within my own state, let lone overseas, at the low point of solar activity. I suppose that means I'll want to pass my General-class license exam, so I can use more of the available bands and modes to stay connected when our atmosphere starts to get a bit more "swampy," so to speak.