The radio is a device used to transmit audio broadcasts to all citizens of Republic City. Many events, such as pro-bending matches, important announcements, and speeches, are broadcast through the use of a radio. It was also used by Amon to rally the nonbenders of Republic City to fight against the benders. After the creation of the Republic City spirit portal, radio frequencies were altered, and radios often did not work properly.
During their stay on Air Temple Island, the White Lotus sentries who were stationed there to guard Korra often listened to pro-bending matches over the radio. When Tenzin forbade Korra to go see a live match, she climbed onto the roof of the sentries' quarters and eavesdropped on the radio broadcast of a Fire Ferrets match. The radio was promptly shut off by Tenzin when he realized that Korra was listening. Later, the White Lotus sentries once again failed to keep track of Korra, who this time had sneaked away from the island, as they were preoccupied with listening to yet another pro-bending broadcast. During this broadcast, Shiro Shinobi announced that the Avatar had joined the Fire Ferrets' team as its waterbender, much to the shock of the sentries and the annoyance of Tenzin.
Amon used the radio to interrupt a program that Korra was listening to while she was training on Air Temple Island to announce to his followers that the United Republic Council had declared the Equalists public enemy number one. However, he urged them over this transmission that the revolution was growing and that nonbenders would no longer have to live in fear.
During the Pro-bending Championship Tournament, Shiro Shinobi witnessed the Fire Ferrets completely dominate the Red Sands Rabaroos, noting to the radio audience that they were very professional in their attacks. But, after relationship problems plagued the Fire Ferrets' ability to work as a team, their next two matches puzzled Shiro Shinobi, as the team could not cooperate to win. However, they were still able to advance to the next round since Korra pulled a "hat trick", knocking the entire opposing team off the ring with one swift blow, which Shiro Shinobi exclaimed excitedly to the radio audience.
The morning of the Pro-bending Tournament finals, Amon threatened the United Republic Council via radio to cancel the event and shut down the arena. However, the final decision was to continue with the tournament. Shiro Shinobi voiced his observations on how the White Falls Wolfbats were breaking official pro-bending rules during their match against the Fire Ferrets and how the officials were not calling any of their infractions. Immediately after the match, strange electrical flashes were seen throughout the arena, which turned out to be Equalists taking out the personnel of the Metalbending Police Force. Shiro Shinobi broadcast the events live to the people tuned in; he continued reporting even when an Equalist approached him in the broadcast booth. His live broadcast was cut short after he was knocked out by that Equalist, who was wearing an electrified glove.
On the day following Korra's capture at the hands of Councilman Tarrlok, the former Chief of Police, Lin Beifong, lay in bed listening to the radio. The program was suddenly interrupted by a news report, spreading word that Avatar Korra had supposedly been abducted by the Equalists. Springing to action at the development, Lin quickly turned off the radio, cutting out the rest of the report.
Several months later, while the Dark Avatar was attacking Republic City during Harmonic Convergence, a panicked Shiro Shinobi relayed to radio listeners what the spirit was doing, before signing off.
Some weeks after Harmonic Convergence, Bumi and Lin used radios to communicate with each other and coordinate their actions during their rescue mission of the captured airbenders in Ba Sing Se. While in search for new airbenders across the Earth Kingdom, Team Avatar was notified on the Future Industries airship radio that a new airbender had been found in Zaofu. Korra later used the Metal Clan's strong radio transmitter to contact Tenzin at the Northern Air Temple, informing him of a new recruit to come his way. She also offered the frustrated master advice on how to get the recruits into shape. During the attack on the Beifong estate, Wei and Wing and Mako used portable radios to coordinate the rescue mission of Korra out of the hands of the Red Lotus.
After the fall of Earth Queen Hou-Ting, Zaheer used Ba Sing Se's city wide radio announcement system to broadcast the end of both the Queen's reign and the class divisions within the city. After learning of Zaheer's plan to murder the Air Nation lest Korra gave herself up, Team Avatar radioed Zaofu and urged them to try to contact the temple's inhabitants. En route to the temple themselves, Korra used their airship's radio to contact Zaheer to agree to his terms. However, the team devised a plan that was once again coordinated through the use of portable radios.
After the invasion of the United Republic of Nations, Mako attempted to use a radio to call for police assistance when the Triple Threat Triad attacked the airbenders near the spirit portal, though the frequency was jammed due to the spiritual energy.
- Prior to Jinora's visit to his library, Wan Shi Tong believed that tiny men resided inside radios, singing and playing musical instruments. This misconception was based on information provided by one of his Knowledge Seekers.