Foundations of Amateur Radio

One of the more perplexing things is the nature of radio regulation. If you're a licensed radio amateur, you'll be familiar with this idea, but if you're not it's bewildering and apparently absurd.

To explain, let me start with a light bulb that your neighbour put on their back porch. It's bright. It's pointing at your house. Like the apparent radiation from a gazillion suns it lights up the bedroom and sleep is hard to come by. Pretty annoying right?

As it happens, radio is a lot like that. If you know physics, it's exactly like that, but I'll ignore that for today.

In our modern world we have many different radios that each rely on a specific, let's call it colour, of light. In radio terms this is known as frequencies or radio bands and the entire collection is known as the radio spectrum. You've likely seen this without knowing. Your 2.4 GHz WiFi has an in-built frequency, 2.4 GHz, as does your 5 GHz WiFi. Your FM radio in the car has frequencies as well, 97.7 on the dial indicates 97.7 MHz. If you have an AM radio, 720 AM refers to 720 kHz.

Hidden in plain sight is why radio is regulated. Those numbers, 5 GHz, 2.4 GHz, 97.7 MHz and 720 kHz are all radio frequencies, or as I suggested, colours. Now imagine turning on a really bright light in the middle of that. All of a sudden your WiFi, FM and AM are wiped out.

It doesn't stop there. As I said, there are many different radios, and sources of radio frequencies.

Radio transmissions come from your mobile phone, Bluetooth headset, microwave oven, computer, television, remote control, key-less fob, power supply, car, power meter, solar panel, battery charger, LED light bulb, and the list goes on. Essentially anything electronic has a radio component. Some of these are transmitting unintentionally, like an electric motor or a switch mode power supply. Other things are transmitting on purpose, your microwave oven, your Bluetooth headset and your mobile phone.

As I mentioned, they're all sharing the same resource, the radio spectrum.

At this point you might ask about the impact of a single transmitter among all that.

Well, there are a few phenomena that you should know about.

Radio waves don't stop. They keep going. There's no boundary. To illustrate that, I have a tiny beacon, a transmitter, that every two minutes sends out a signal that shows my amateur callsign and location. It uses 10 milliwatts. To give you a sense of scale. A typical incandescent light bulb is about 60 Watts. My transmitter uses sixty thousand times less power. It has been heard 13,455 km away, about a third of the way around the planet. I will point out that different frequencies can be absorbed differently depending on how they're used, but you cannot rely on the idea that any radio frequency stops anywhere.

Another phenomenon is a thing called harmonics. Radio waves not only share the same space or spectrum, they're related to each other. Unless you take very specific precautions, a transmission made at 100 MHz, will be heard at 200 MHz, 300 MHz, 400 MHz, 500 MHz and so-on. While each of those transmissions gets progressively weaker, they still exist. Now imagine that someone else is using one of those other frequencies to communicate emergency information. It's like their backyard just got hit with a bright light.

To give you a specific example of why this can matter. Consider a radio amateur who uses 7 MHz. This is a licensed amateur radio frequency. Unless that amateur takes specific precautions, the 16th harmonic for 7 MHz is 112 MHz. If that doesn't mean anything to you, it's in the middle of the so-called air-band, frequencies used by aircraft around the planet to talk to each other and the ground. Very bad things could happen if safeguards weren't made.

As a result, radio is highly controlled and regulated. I'm not going into the laws or legalese here, given that this is a global phenomenon and the rules in their specifics are different in each country. There's a whole hierarchy of regulation, arrived at by international cooperation and agreement.

These regulations are not identical in each country, far from it. Each country has their interpretation of the rules and balances those with its own use of radio. For example WiFi, a very popular use of the radio spectrum, can be bamboozling in the endless variation of something so seemingly simple.

Most of this is invisible to most people. You go to the store and buy a WiFi base station and you go on your way. With the advent of online shopping, you can click "buy" on any window, regardless of which country the device comes from. If you're not careful your shiny new device, imported from somewhere is actually illegal in your country and fines and punishment can be severe.

If you start digging into this, you'll come across rules that for example say that you cannot change the antenna on a particular device. This is because the transmission power of the hardware is strictly regulated so it doesn't interfere with other users. Changing an antenna has the potential to change a number of aspects of your device. It can potentially amplify harmonics that were suppressed by the existing antenna. It could increase the perceived power level and overload other receivers. On a shared frequency it might lock out other users. This is why for example across the European Union, Private Mobile Radio on 446 MHz, or PMR446, a unlicensed radio provision that allows for business and personal use, has heavily regulated hardware. These devices are not permitted in places like Australia, the USA and Canada because in those countries, 446 MHz is used by radio amateurs and military radar systems.

This is why you'll find equipment like mobile phone amplifiers and jammers are heavily regulated and controlled. You'll also discover that transmitting on public frequencies like the FM broadcast band is a massive No-No. I'm not going into the so-called "FM capture effect", but the impact is that your personal transmitter needs to be locally louder than the station you're trying to break into and that in turn means that your little transmitter isn't so little any longer and the neighbours and the regulator will notice and come looking for you.

Before this begins to sound like I'm stopping anyone from experimenting, let me point out that licensed radio amateurs have been granted permission to experiment in this magical radio play ground. Of course there are very strict rules around this, but perhaps now there is an understanding on why that might be the case.

The more you dig in, the more stuff there is to explore and learn. As a radio amateur you are granted the keys to the city as it were.

If this information was shared with you after you asked a simple question, perhaps it's time to stop what you're doing, consider the impact on your wallet and equipment and in some cases freedom, and instead explore the idea of becoming a radio amateur where you can legally play with this stuff.

If you're already licensed, perhaps this will help to explain to others why.

I'm Onno VK6FLAB