The Wonderful World of Shortwave

I, like many others, have been fascinated by the radio from a young age. For me, it's something about the invisible waves travelling at unimaginable speeds through us at every moment, carrying the information that we listen to through our radios. The fact that a radio is like a set of eyes into a seperate, invisible dimension. Whether you share my fascination, or if you've never touched a radio in your life, I hope that this rather short journey through history and physics will make you a little more curious about the oldest broadcast mass media we have.

I will begin, of course, with a short history lesson. The word "radio" comes from the Latin term "radius", meaning a beam of light. Radio waves were theorised in 1867 by James Clerk Maxwell, and subsequently discovered in 1887 by Heinrich Hertz (who we have named a unit for frequency after).

Italian inventor Guglielmo Marconi began to experiment with radio waves in 1894, at the age of 20, and by 1897 he was transmitting morse code almost 5km wirelessly, and made the world's first transmission over the open sea, from Flat Holm island to Lavernock Point in south Wales. However, just transmitting over a few kilometres of water wasn't enough to satisfy Marconi. No, he wanted something more - to send a wireless telegraph across the Atlantic Ocean.

By this time, transatlantic telegraph cables were old news. The first one had been laid in 1856; that was almost 50 years ago! Marconi wanted a new and shiny technology to compete with the cables. He set up transmitting stations in Cornwall, England; and County Galway, Ireland; as well as a recieving station in Newfoundland. He conducted his first test of the system in 1901, across 3,500km of ocean - and heard the signal!

How did this work? You may recall from your physics lessons at school that electromagnetic waves can only travel in a straight line. Surely, transmitting radio waves 3,500km, the curvature of the Earth will block the signal? Correct! However, there is another property of electromagnetic waves that makes long transmissions possible. They bounce. You can see this behaviour easily for yourself by looking in a mirror: visible light is a type of electromagnetic wave, and for you to be seeing yourself in the mirror, the light must be bouncing off you, into the mirror, and into your eyes. But there isn't a huge, shiny mirror surrounding earth, or else we wouldn't be able to see the stars, or the sun. But light doesn't need to be affected by something visible to be changed - look at how light refracts through a glass of water, or how the air seems to wobble above the ground on a hot day. Radio waves are able to reflect off a part of Earth's atmosphere called the ionosphere, to be bounced back down to the surface and received by a receiver.

The ionosphere is situated in Earth's upper atmosphere, from about 70km to 400km. It's layers of ionised air, where ultraviolet radiation from the Sun knocks electrons off the atoms in the upper atmosphere. This ionisation is stronger in the day, and weaker in the night. The level of ionisation also depends on how active the Sun is; the Sun is on an 11-year cycle between being very active, and very inactive. Higher levels of activity, such as solar flares and the resulting geomagnetic storms, increase the level of ionisation in the atmosphere. The ionisation density affects waves in much the same way water affects visible light waves, meaning radio waves can be refracted or totally internally reflected in the ionosphere.

However, it isn't all good. Some layers in the ionosphere also have the ability to absorb radio waves. Primarily the D region (with the other relevant regions being E and F) is responsible for absorbing transmissions. This not only means that your transmissions won't be reflected very well - they won't be reflected at all!. This very significantly reduces the range of radio transmissions, especially amateur ones which don't have access to enormous transmitting power and towering antennas. In the D layer, the free electrons become excited by radio waves, causing energy loss of the waves. With one electron, this energy loss is not noticable, but with millions of electrons, it becomes noticable quickly. At times of intense solar radiation, radio blackouts can even be caused, completely killing any hope of listening on shortwave bands!

Most of what I have been saying about the ionosphere, reflection, and absorption mainly applies to relatively low frequencies compared to what we use today. But there is also a phenomenon called the sporadic E region. This is a very rare region of the ionosphere which has the capability to reflect higher frequencies than normal, up to 450MHz rarely! This opens up much further range communication for amateur operators who use those affected frequencies.

All this is to say, that as a byproduct of physics, radio is constantly changing. One moment you may be picking up nothing, and the next moment you may be listening to an amateur enthusiast transmitting their favourite Beatles tracks, or a pirate station advertising a rave, or propaganda from a country on the other side of the world. Or, you could be picking up one of my favourite things to listen to on the airwaves: a numbers station.

Leading up to and during the Great War, there was a need for espionage, which continued for decades into the cold war and the 21st century. Spies are one of the most powerful weapons a country has access to, and the brand new wireless communication method of radio was a promising way to communicate in secret. Radios are cheap, long range, and encrypted messages can be transmitted using a form of encryption called a one-time pad. To outside observers, a numbers station is just a voice saying numbers. To the intended recipient however, the message is able to be decrypted using their copy of the one-time pad, and their orders have been given.

Although most numbers stations have long stopped broadcasting, including some of the most famous examples (the Lincolnshire Poacher comes to mind) there are still many that you are able to listen to today. Enigma 2000 compiles current information on numbers stations with a newsletter still published regularly, and Priyom.org provides a real-time schedule of when numbers stations are broadcasting, along with information about the induvidual stations themselves. One of my favourites to tune into is E11 "Oblique", which is broadcast from Warsaw, Poland; so often receivable from Britain. It says groups of numbers in english using a robotic voice, and separates the numbers with the word "oblique", hence the nickname.

Unusual things on shortwave bands are also not uncommon to hear. I was listening once during good conditions and heard the sound of bagpipes through my radio, which shortly transitioned into smooth jazz, and then a man started to speak. I couldn't make out what he was saying, but I looked it up later and confirmed that I had been listening to an australian maritime weather station.

But I could go on for hours about all the weird things I've found on the airwaves. Chinese jammers to block out the signal of other stations, terrible music stations, even cults broadcast their ramblings out. Everything I've heard has been dependent on my location, my equipment, my antenna, the weather, and the ionic conditions. You won't hear all of the same stations as I have, and I likely won't hear all of the stations you could listen to!

So, I've convinced you. You can picture yourself spending hours moving a dial round, stopping at any interesting frequencies you find along the way. How do you get into this hobby? Well, the great news is that it's free! There are websites which host live radios which anybody can tune into and select the frequency they want to listen on. These are called webSDRs (SDR stands for software defined radio), and the one I use most frequently is the Utwente webSDR.

The obvious downside with webSDRs is that you need an internet connection to access them. One of the reasons I love radio is because I don't need a screen - or at least any more of a screen than the 7-segment display on my radio. So if you're more of the prepper type, or if you just want to be off your phone more like me, then you might want to consider buying a dedicated radio.

Google "shortwave radio for sale" and you'll be bombarded with suspiciously cheap radios and ridiculously expensive radios. You may be tempted to go with one of the no-name Amazon models, but be warned: these are very low quality and have bad reception and reliability. There do exist dedicated buying guides online (this one looks decent) but I'll attempt to go over a few here.

For those really on a budget, you can go with the same radio as my first one: the Tecsun R9012. Tecsun are a recognised name in the world of shortwave, making great radios such as the PL-660. But the R9012 only costs around £20, and the features reflect that. It does FM, mediumwave, and 10 bands of shortwave. It has an internal antenna with nowhere to plug in an external one. It does wide mode only: no sideband mode means that you won't be able to listen to numbers stations or most amateur transmissions. It has no digital display, and in fact no digital features, so if you want to find the next station you'll have to just slowly move the dial upwards manually. The way I've been describing it makes it sound terrible and featureless, but honestly? For £20 you can have a pocket-sized, low power radio which can pick up signals from around the world - even if you can't read the exact frequency to find out what exactly you were listening to.

The Tecsun PL-330, is a popular choice online, though not one which I own. It's more expensive than the R9012, at £50-100. However, if the feature list of the R9012 made you yawn, the PL-330 may be more suited to you. It has longwave, as well as FM, MW, and SW like the R9012. It's also a digital radio, and has sideband capability, so numbers stations and amateur transmissions are no longer out of reach. You can also connect an external antenna for better reception, and as it's digital it can automatically scan for transmissions. If I was a first-time radio buyer, this is probably what I'd go with.

The radio I use is the Sony ICF-2001d. Produced from 1985 to 2003, and pioneering early synchronous detection on consumer radios during that time. It definitely doesn't fit in a pocket, but it has (almost) all the features I could ever want. It does FM, longwave, mediumwave, and full shortwave. It has air band on VHF to tune into aeroplanes going by. It has a huge internal antenna, and if that isn't enough, then not one but two external antenna ports! It's a thing of beauty, and I love using it, but to face the facts: they can go for pretty high prices online, and there are simply radios that are better value for money today. If you do have access to an ICF-2001d though, don't hestitate to learn its features and have fun with a beautiful radio!

Maybe you want to listen to more than just shortwave, though. Maybe you want to listen to some shortwave, but also the amateur bands on VHF and UHF, or perhaps you want the option to set up an ADS-B receiving station. There is a magical device which will allow you to do all of these things with the same radio: a software defined radio! An SDR is a small USB dongle that you plug into a computer. On the opposite end from the USB is an antenna jack. If you connect an antenna to one side of the SDR, and plug the other side into a computer with software such as SDR++ installed, and you can type in whatever frequency you want, with whatever demodulation you want! The most popular SDR is the RTL-SDR, which is also what I own. It'll set you back about £50, not counting any external equipment. It's BYOAFCDKM (Bring Your Own Antenna, Filter, Computer, Display, Keyboard, and Mouse) of course, but most people own a computer, and with a bit of SMA coaxial; some copper wire; and a soldering iron; you can make almost any type of antenna, offering unparalleled versatility.

This post was written in November 2025 by Noa