Antenna (electronics)
An antenna is a crucial electronic device primarily used for transmitting and receiving signals such as radio, television, and telecommunications. Typically constructed from rods or wires, antennas operate by picking up electromagnetic radiation, or radio waves, which travel at the speed of light from their source. These devices are integral to almost all electronic equipment, from cell phones to livestock identification microchips. Antennas can vary in size; while broadcasting antennas may reach hundreds of meters tall, receiving antennas can be as small as a metal rod or even embedded within devices.
The principles of antennas are based on electromagnetic theory, with historical roots tracing back to discoveries by James Clerk Maxwell and Heinrich Hertz, who identified the existence of radio waves. Over time, innovations in antenna technology have paved the way for modern communication, including wireless networks, satellite dishes, and Bluetooth devices, making antennas ubiquitous in daily life. Their influence is so profound that many people use communication technologies without realizing the role antennas play in their functionality. Understanding antennas provides insight into the evolution of communication technologies that have shaped contemporary life.
Antenna (electronics)
An antenna is a device that is used to transmit and receive radio, television, or telephone (both land line and cellular) signals. Most are made of rods and/or wires. Any device that transmits or receives radio waves must contain an antenna of some sort; therefore they are found in almost all electronic devices, including the microchips that are used to positively identify livestock or pets.
Antennas pick up electromagnetic radiation, or light waves, that travel at the speed of light from their origin in the form of radio waves. The electrons in the current move back and forth along an antenna, taking a radio or television program with them. The electronic components inside a receiving device, such as a television or a stereo, convert that signal to something that can be seen and/or heard. Broadcasting, or transmitting, antennas are very large structures, sometimes stretching hundreds of meters into the air. Receiving antennas, however, can be as small as a metal rod or an unseen wire inside a cell phone. Signals can travel three ways:
In a straight line from the transmitter to the receiver, just like a beam of light
In a ground wave, which can navigate the earth's curvature for some distance, or
They can shoot off of the earth's electronically charged ionosphere and return to the ground. This method works best at night, when there is less signal interference.
Brief History
In 1864, James Clerk Maxwell discovered that electricity and magnetism were the same force. He ultimately proved that light is an electromagnetic wave. German scientist Heinrich Hertz was working to prove Maxwell's theory when he discovered radio waves, which were known as Hertzian waves for a time. An August 14, 1894, English physicist Oliver Lodge conducted a demonstration at Oxford University that used radio waves to signal from one room to another. Lodge filed a US patent for electric telegraphy on Feb. 1, 1898, to use Hertzian waves to transmit messages between various locations.
Despite the efforts of a number of pioneers in radio technology, it was the Italian inventor Guglielmo Marconi who has been given historical credit for inventing the radio, largely because he was a better showman than his scientific peers. As a young boy in Italy, he replicated the experiments of Hertz. On December 12, 1896, Marconi demonstrated his wireless radio technology in London. At the heavily publicized event, Marconi tapped a telegraph key in one part of a room while his assistant walked around a room with a receiver. Every time he tapped a telegraph key, a bell rang. Five years later, on December 12, 1901, Marconi sent the first electronic communication across the Atlantic Ocean.
Other radio pioneers, such as Rev. Joseph Murgas, pastor of the Sacred Heart Church in Wilkes-Barre, Pennsylvania, have been largely forgotten by history. Murgas and his partners nineteen miles away in Scranton built antennas in both locations. They could send long-range telegraph signals at a rate of fifty words per minute. In contrast, Marconi's system could only send fifteen words per minute.
Early transmitters and receivers looked nothing like modern devices. Hertz used a spark-gap oscillator, which includes two zinc balls attached to short lengths of copper wire. Marconi used glass tubes with metal filings.
One of the largest antennas ever constructed in the early days of radio was the Blaw-Knox antenna in Mason, Ohio. The joint venture between RCA, General Electric, and Westinghouse served as the broadcast transmitter for WLW-AM Radio, which later called itself The Nation's Station because it received government permission to operate at an experimental 500,000 watts. The 831-foot antenna made the station's signal ten times stronger than any other station in the country, and President Franklin D. Roosevelt formally opened it on May 2, 1934. It was so powerful that locals reported hearing broadcasts on barbed wire fences, water faucets, and radiators. The Blaw-Knox antenna remained in operation until March 1939, when the Federal Communications Commission ordered the station to return to broadcasting at 50,000 watts, due largely to interference complaints from smaller stations. The tower is on the National Register of Historic Places. By contrast, the receiving antennas that are used in microchips implanted into pets and livestock are no larger than a grain of rice.
Impact
Radio technology has come a long way from the spark and wire experiments conducted by Heinrich Hertz and his late-nineteenth century contemporaries, or the forgotten experiments conducted by Father Murgas from his church rectory in Pennsylvania. The antenna, and more specifically radio technology in general, has become so ubiquitous in daily life that most people hardly ever think about it. Antennas are built into nearly everything people use to transmit and receive communications, including cellphones, televisions, radios, and wireless routers. Without the antenna, many modern advancements in communications technology would be impossible.
Satellite dishes used to watch television or compile weather information are themselves antennas, and cell phones and smartphones run on radio waves. Modern wireless networks translate data into radio signals and transmit it using antennas. The networks then transmit the data to the Internet using wired Ethernet connections. Wireless routers receive information from the Internet, translate it into radio signals, and send them to a wireless adapter. Bluetooth devices for high-quality streaming use radio waves to connect a phone to a computer, and Bluetooth-enabled devices communicate via shortwave radio technology. The nostalgic image of a 1930s-family gathered around the living room radio might seem antiquated by modern standards, but radio remains the foundation of modern communications technology.
Bibliography
Alfred, Randy. "Dec. 12, 1896: Marconi Demos Radio – Dec. 12, 1901: Marconi Transmits Across Atlantic." Wired, 12 Dec. 2011, www.wired.com/2011/12/1212marconi-radio-demo-transatlantic/. Accessed 5 May 2022.
Brain, Marshall, Tracy V. Wilson, and Bernadette Johnson. "What Is WiFi?" How Stuff Works Tech, computer.howstuffworks.com/wireless-network1.htm. Accessed 5 May 2022.
The Doc. "How Heinrich Hertz Discovered Radio Waves." Famous Scientists, www.famousscientists.org/how-hertz-discovered-radio-waves/. Accessed 5 May 2022.
"Heinrich Hertz." Famous Scientists, 23 Nov. 2015, www.famousscientists.org/heinrich-hertz/. Accessed 5 May 2022.
"How Do Pet Microchips Work?" Petfinder, www.petfinder.com/dogs/lost-and-found-dogs/how-pet-microchips-work/. Accessed 5 May 2022.
"James Clerk Maxwell." Famous Scientists, www.famousscientists.org/james-clerk-maxwell/. Accessed 5 May 2022.
"Rev Joseph Murgas Historical Marker." ExplorePAhistory.com, 2019, explorepahistory.com/hmarker.php?markerId=1-A-3A1. Accessed 5 May 2022.
"Learn about Bluetooth: Bluetooth Technology Overview." Bluetooth.com, 2022, www.bluetooth.com/learn-about-bluetooth/tech-overview/. Accessed 5 May 2022.
Woodford, Chris. "Antennas and Transmitters." Explainthatstuff.com, 6 Oct. 2021, www.explainthatstuff.com/antennas.html. Accessed 5 May 2022.
Woodford, Chris. "Electromagnetic Spectrum." Explainthatstuff.com, 24 Mar. 2021, www.explainthatstuff.com/electromagnetic-spectrum.html. Accessed 5 May 2022.