Learn / Guide 1
What is radio listening
Listen to radio out of interest in the signal itself: who is transmitting, from where, and how it arrived. You can start today, in your browser, without buying anything.
beginner 5 min read
Listen out of curiosity
Radio listening is turning on a receiver and hunting for signals out of interest in the signal itself: who is transmitting, from where, in what mode, and how that reached the antenna. In English the most common term is SWL, for shortwave listening. When the goal is to catch distant or rare stations, the name becomes DX.
No license is required to listen. A license is for transmitting. Listening and sharing what you heard are different things, and there are a guide here just about this.
I am Fernando, PU2TQF, an amateur radio operator in São Bernardo do Campo. This site exists because almost everything about radio can be learned before having any equipment, using receivers that other people leave open on the internet and public propagation data.
What you can hear
| What | How it sounds | Where to look |
|---|---|---|
| Shortwave stations | news and music from other countries, in various languages | bands between 5.9 and 26.1 MHz |
| Distant AM stations | stations from other states and countries, at night | 530 to 1,700 kHz |
| Radio amateurs | voice conversation, telegraphy, digital modes | 7.0 to 7.3 MHz, 14.0 to 14.35 MHz and several other bands |
| Time signals | a tick per second and the spoken time every minute | 5,000, 10,000 and 15,000 kHz |
| Aviation | pilots and towers, in AM | 118 to 137 MHz |
| Aircraft in data | position, altitude, and speed (ADS-B) | 1,090 MHz |
| Signals from space | Space Station, radiosondes, satellites | 145.800 MHz, 400 to 406 MHz, 137 MHz |
| Maritime weather | facsimile weather charts | fixed shortwave channels |
Part of this is sound that anyone understands. Part is data, and needs a program to turn into text, map, or image. Both count as listening.
The reason for still doing this
The internet delivers any audio in the world with perfection, and precisely for that reason it lacks the same charm. On the radio, the signal left an antenna, went up, bounced back from the ionosphere and came down thousands of kilometers away, without cables and without an operator in between. It changes with the time of day, the season of the year and the mood of the Sun. The same frequency that is dead silent at noon can be packed at midnight.
Whoever listens ends up learning physics, geography, and a bit of various languages along the way. And they learn to read the spectrum: they glance at a blotch on the screen and know whether it is voice, telegraphy, or the neighbor's switching power supply.
For anyone thinking of becoming a radio amateur, listening beforehand is the best preparation. You discover who uses each band, how a QSO starts and ends, and how people identify themselves, all before pressing the transmit button for the first time.
It also has a practical side. Radio keeps working when the grid goes down. In an emergency, shortwave and radio amateurs stay on the air with a battery and a piece of wire.
Start today, through the browser
A WebSDR is a real receiver, connected to a real antenna, that the owner put on the internet. You open a page and control the tuning from there. There are three main families:
- KiwiSDR: covers 10 kHz to 30 MHz, meaning long, medium and entire short waves. There are hundreds scattered around the world, several in Brazil.
- OpenWebRX: depends on the owner's equipment. Many cover VHF and UHF, and some already decode digital modes right on the page.
- Classic WebSDR: the oldest one. The one at the University of Twente in the Netherlands handles hundreds of people at the same time.
One detail changes everything: you hear what the antenna over there hears. A receiver in Europe shows European propagation. To know what would reach your home, choose a Brazilian receiver, preferably in your state.
A first itinerary
- Open the public KiwiSDR list and choose a receiver in Brazil.
- Type
10000and select the AM mode. This is WWV, the time signal station of the United States. If nothing appears, try15000during the day or5000at night. - Type
7074and switch to USB. The beeps that turn on and off every 15 seconds are radio amateurs in FT8. - At night, roam between 7,050 and 7,200 kHz in LSB. This is where you hear amateur operators chatting in Portuguese and Spanish.
- At night, scan from 5,900 to 6,200 kHz and from 9,400 to 9,900 kHz in AM. These are two international broadcast bands.
Note down what you find: date, time in UTC, frequency, mode and a line about what you heard. The logbook is the oldest habit of the hobby, and it is what shows, after a few weeks, how the bands behave.
Where to go next
The upcoming guides follow an order. First the spectrum map, to find out who lives in each band. Then the use of remote receivers and the reading the waterfall display, which is the color screen that all of them show. Next comes the propagation, which explains why yesterday's band is not the same today.
Own receiver and license are placed near the end on purpose. Both make more sense after a few weeks of listening, when you already know what you want to hear.