Ham Radio
Ham Radio
Overview
- Ham radio, formally amateur radio, is two-way radio communication by licensed hobbyists on frequency bands set aside for them. Operators talk by voice, send Morse code, or pass text, images and data through a computer, across town, across the world, through satellites, and to the International Space Station.
- What is Ham Radio? ยท ARRL is the overview from the national association for amateur radio in the United States.
Context
- Amateurs were building and operating radio stations in the first decades of the twentieth century, soon after radio itself. The ARRL was founded in 1914 to relay messages between amateur stations across distances no single station could reach.
- The origin of the word "ham" is uncertain. A common account is that professional telegraphers used it as an insult for clumsy operators, and amateurs later adopted it with pride.
Key Principles
- A license to transmit. In the United States, an operator must pass an FCC examination before transmitting on the amateur bands. The entry-level license is the Technician class.
- Listening needs no license. A receiver, including a shortwave set built from a kit, can pull in distant stations without any license. Listening of this kind is called shortwave listening.
- No business. Amateur bands are for personal, non-commercial communication.
Mechanism
- On the shortwave (HF) bands, signals bounce between the ionosphere and the ground in hops, so a modest station can reach the other side of the planet. How far a band reaches changes with the time of day, the season, and the sunspot cycle.
- A good ground connection improves a simple receiver: driving a metal rod into the earth gives the antenna circuit a return path.
Examples
- Emergency communication: when regular networks failed after the 9/11 attacks and during Hurricane Katrina, amateur operators carried messages for public service agencies.
- Contacting the International Space Station, bouncing signals off the moon, and working amateur satellites.