Foundations of Amateur Radio

A recurring question for people who are not yet, or newly licensed is something along the lines of: I have a friend who is 400 kilometres away, can I talk to them on my hand-held 2m radio?

This particular question arrives in different forms, but generally along the lines of attempting to communicate between point A and point B at some or other distance.

The responses, on social media at least, less so on-air, are often very technical, or offer the advice to get a license, or to get a clue, or the question is ignored or dismissed. That's not helpful, or fair. The person asking the question has expressed an interest in our hobby and is looking for help.

As a basic set of answers, if you're both standing on the ground, you'll generally be able to talk about 5km using your hand-held. Stuff between you like buildings and hills will lower that distance. If you both stand on a hill, you can talk further away. As an aside, you can talk to the International Space Station with a 2m, 144 MHz hand-held because there is nothing between you and it when it's overhead, even though it's 350 km away.

If you cannot see between the two, then an intermediate radio, a repeater, can facilitate the connection. It needs to have visibility to both radios at the same time. The higher the middle point, the further the distance. For example an antenna at 350m above the ground has a so-called radio horizon of 77km and I should point out that that's actually 15% further than actual line of sight. As long as both ends are within that radius, you should be pretty much good to go.

You can theoretically string together a whole bunch of repeaters, along a road for example, but more often than not, for distances greater than line of sight you need to invoke radio frequencies that your 2m hand-held won't do. These frequencies are generally referred to as HF and is generally anything between 3 and 30 MHz. Radio transmissions on these frequencies mainly use the ionosphere to make contact possible and you can make contacts from as close as next-door, to as far as the opposite side of the world.

The ionosphere is subject to weather in much the same way as clouds and rain. The variation in the ionosphere is driven by the sun, not by wind and humidity, and it varies throughout the day as the sun rises and sets. Communication varies depending on where the sun is and several other factors well outside this explanation. As the ionosphere changes, usable frequencies change. Something that worked one moment might not the next because the ionosphere changed.

As a licensed radio amateur you have access to many different frequencies and depending on the state of the ionosphere you can change frequency as required to alter your station to suit the conditions. You can think of it as adjusting your sail depending on the wind direction, to get from A to B.

One final point. Antennas are many and varied. They are designed for specific purpose and will react differently depending on how they're designed, built, installed and used, so the variation you're stepping into is enormous.

This hobby is nothing like dialling a phone number and making a connection, it's all about the experience and the learning. If that tickles your fancy, you're already halfway to becoming an amateur. Welcome.

I'm Onno VK6FLAB