Foundations of Amateur Radio

When you begin your amateur radio journey, one of the first things you learn about that's not directly involved with radios and antennas is the ionosphere and its impact on long distance communications. Immediately after that you are more likely that not to be introduced to the biggest plasma experiment in our backyard, the Sun.

With that introduction comes information about solar flares, solar flux, sunspots, geomagnetic storms, coronal mass ejections as well as the solar cycle, the solar index and associated propagation forecasts.

Before I dig further, I will point out that I'm mentioning this with the ultimate aim for you to get on air and make noise, so fasten your seat-belt and let's go for a ride.

The Sun is big. If it was hollow, it could fit more than a million Earths inside. The Sun accounts for 99.8% of the total mass of our entire solar system. About 73% of the Sun's mass is hydrogen, about 25% is helium and the rest, about 1.69% is made up of all the other heavier elements, both gasses and metals, which add up to around 5628 times the mass of Earth.

The Sun rotates. Counter-clockwise. Since it's mostly plasma, it doesn't rotate like Earth does. The equator takes about 24 days, the poles around 35 days and because its rotating on an angle of about 7.25 degrees from Earth's rotation axis, we get to see more of the solar north pole in September and more of the solar south pole in March.

Earth orbits the Sun in a year, but it's not a circular orbit. We're closest to the Sun in December and furthest from the Sun in June. It takes about eight minutes and 19 seconds for a photon leaving the Sun to reach Earth, but that same photon can take between 40,000 and 170,000 years to travel from the core where two atoms were heated and compressed to fuse into a new element releasing a photon and heat. It takes this long because the photon keeps bumping into other atoms along the way. While we're at it, consuming about 4 million tons of hydrogen per second, the Sun will take another 5 billion years to consume all the available hydrogen.

Whilst we experience the Sun as a source of light on a daily basis, as a radio amateur you know that light is just one tiny part of the electromagnetic spectrum. It should come as no surprise that the Sun is radiating across all frequencies all the time, only some of which is visible to our naked eye.

As an aside, it's interesting to note that our eyes are essentially translating light into electricity, or said differently, your eye converts radio spectrum into electricity, something which your radio antenna also does.

Back to the Sun.

I'm highlighting this level of solar complexity because there's so much talk about the A index, the K index, the SFI, the solar cycle and propagation by experts and amateurs that it's easy to hide behind those numbers and think that a low A between 1 and 6, a low K of 0 or 1 with an SFI above 100 will give you the propagation you're looking for.

If you think for a moment that the weather forecaster has a difficult job accurately telling you if you need to postpone your outdoor activation because of rain or snow, then you can begin to understand just how complex the interplay between the Sun and our ionosphere is. And I haven't even mentioned that the ionosphere isn't static either.

It's important to remember that the cute little weather icons you see on the TV news are just as much an indicator of expected weather as the A, K and SFI numbers are for the Sun and its impact on radio propagation. They give you an idea of what might happen, but it doesn't mean that on any given day something completely random and isolated happens that just affects your station and the path that a radio signal took from your antenna to that other rare DX station.

Just like it would be smart to take an umbrella with you when there's rain forecast, it's also smart to consider the bands you want to operate next time you go on air with a particular solar forecast, but just because it might rain, doesn't mean you're guaranteed to get wet.

So, in other words, wait for it, get on air and make some noise!

I'm Onno VK6FLAB