Propagation predictions and operating your radio

Foundations of Amateur Radio

Today propagation is what it is, yesterday it was different and tomorrow it will be different again. It's one of the fundamental aspects of amateur radio.

We talk about propagation on air, like we do the weather. Rain, sun, snow or storm, there's always something. Of course most of those weather events have no impact on radio. A rain drop isn't going to make a great deal of difference to a HF signal, other than potentially making the operator wet, or creating a short-circuit in an unexpected way.

Propagation on the other hand has little or no effect in day-to-day life, other than your GPS, mobile phone or other electronic device. In radio however, propagation makes the difference between only hearing your neighbours and speaking to another station on the other side of the globe.

In the past I've mentioned that if you skip a stone across a lake, you get a good idea about how radio waves bounce off the ionosphere and in doing so, make it possible to hear and be heard beyond the line of sight of your antenna.

A stone is a fixed object and water has a pretty uniform density, so you get mostly predictable results. The ionosphere is not uniform and radio waves are not fixed, so the result is anything but predictable.

That said, a great number of people are working on providing propagation prediction tools in an attempt to provide us with somewhat more of a reliable outcome. Once you step into this area, you'll come across the A and K indices, the Solar Flux and Geomagnetic and Solar Flare numbers.

You'll find websites like solarham.com, bandconditions.com, spaceweather.tv and many others. Sometimes they'll even agree with each other - which is interesting in itself, since the source of actual data is pretty limited. We have the Ionospheric Prediction Service or IPS in Australia, in the US there's the National Oceanic and Atmospheric Administration, or NOAA.

All this is to attempt to quantify what the sun is doing and how this affects the ionosphere and in turn our experience as radio operators.

If you know anything about predicting the weather, that is, what is the temperature going to be today and is it going to rain, you'll understand that predicting solar activity and its impact on us is a less than perfect experience. In 1959 we managed to snap the first images of the far side of the Moon, it took until 2011 for us to do the same with the sun.

Many of our predictions are really observations and imperfect ones at that, coming from the two STEREO spacecraft, one orbiting the sun ahead of the earth, the other behind the earth, combined they manage to cover the back of the sun.

In the end, the predictions on carrying an umbrella or not are like predicting whether to operate or not. It's a prediction. Nothing beats turning on your radio and having a go.

I'm Onno VK6FLAB