Radio

**Radio** is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by a radio receiver connected to another antenna. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing and other applications.

## Overview

Radio waves are radiated by electric charges undergoing acceleration. They are generated artificially by time varying electric currents, consisting of electrons flowing back and forth in a metal conductor called an antenna, thus accelerating. In transmission, a transmitter generates an alternating current of radio frequency which is applied to an antenna. The antenna radiates the power in the current as radio waves. When the waves strike the antenna of a radio receiver, they push the electrons in the metal back and forth, inducing a tiny alternating current. The radio receiver connected to the receiving antenna detects this oscillating current and amplifies it.

As they travel farther from the transmitting antenna, radio waves spread out so their signal strength (intensity in watts per square meter) decreases, so radio transmissions can only be received within a limited range of the transmitter, the distance depending on the transmitter power, antenna radiation pattern, receiver sensitivity, noise level, and presence of obstructions between transmitter and receiver. An omnidirectional antenna transmits or receives radio waves in all directions, while a directional antenna or high gain antenna transmits radio waves in a beam in a particular direction, or receives waves from only one direction.

Radio waves travel through a vacuum at the speed of light, and in air at very close to the speed of light, so the wavelength of a radio wave, the distance in meters between adjacent crests of the wave, is inversely proportional to its frequency.

From its beginnings, radio was primarily used for communication purposes, due to its speed and ability to reach far distances. The power to transmit information instantaneously is seen as a great advantage, not only in military terms, but also for peacetime applications.

## Radio in the New World

### Third Civilization Area and Outside Civilization Area

Remote communications were established using magical means such as the Magical Communication Device. As a result, only nations with magical ability or resources, had access to such devices, such as the Parpaldia Empire. However, these devices were considered inferior to their technological versions.

### Second Civilization Area and the Gra Valkas Empire

Mechanized civilizations such as Mu did possess primitive radio systems that were bulky and had limited range. After meeting with Japan, their radio technology increased dramatically as they were able to fit communication devices onto smaller vehicles, such as the Marin fighters. Radar technology had also improved with the introduction of outdated laptops to use as their computer cores.

The Gra Valkas Empire also possessed radio equipment, but these were bulky and outmoded due to their reliance on the vacuum tube. Both their radio and radar systems became easily jammed by Japanese Electronic Countermeasures.

### First Civilization Area

Nations such as the Holy Milishial Empire still rely on magical means, and use more powerful magical communication devices and detection systems. However, as proven during the Great Naval Invasion of Japan, these devices can still be jammed by Japanese Electronic Countermeasures.

### Japan

Hailing from the 21st century, Japan is at the forefront of radio communications and all types of applications, such as radar, satellite and remote controls.