What is radio transmission?

Radio transmission technology has had a huge impact on the development of communication around the world. From broadcasting music and television to wireless computer networks and automatic gates, radio is an unsung hero of the modern world. We all use radio transmission all the time, probably without realising it!

For example, every time you push a button on your key to unlock your car, that’s radio waves. They probably shouldn’t even be called ‘keys’ any more – when was the last time you physically put a key in a car door?

How does radio transmission work?

Radio transmission is the process of sending data from one place to another through the air using radio waves. Radio waves are a type of electro-magnetic wave that is undetectable in the air. You can’t see them, smell them, hear them, or touch them.

Data, such as a recording of someone’s voice, is encoded onto the radio waves by a transmitter. It is then sent through the air to a corresponding receiver. The receiver decodes the data in the radio waves and converts it back into a usable format. That’s how someone speaking into a microphone in a radio station studio gets their voice into your car’s radio.

History of radio transmission

Radio transmission uses radio waves to move information from one device to another. Radio waves are a type of electro-magnetic wave. The existence of electro-magnetic waves was first proven by the German physicist Heinrich Hertz in 1886.  His work built upon earlier theories by the Scottish mathematician James Clerk Maxwell [1].

The Marconi revolution

By the 1890s, “Hertzian waves” (it took 20 years for the term ‘radio’ to come into common usage [2]) were being explored as a means of communication. Some physicists thought that the technical limitations were too great. The equipment needed was very delicate, and transmission required a lot of power to send messages relatively short distances.

The next big step forward came from the Italian inventor Gugliemo Marconi in 1895. While experimenting in his parents’ attic, he successfully built a wireless telegraph machine [3]. The machine allowed him to transmit Morse code over radio waves. Marconi developed the technology to the point that he was able to transmit messages over distances up to two miles, and over hills [4].

The Italian government were uninterested in the technology. As a result, Marconi headed to the United Kingdom. There, he founded the British Marconi company in 1897 and began marketing his wireless communication technology commercially. In 1899, the American subsidiary of the company was founded. Marconi went on to dominate ship-to-shore and transatlantic communication for almost two decades.

Transmitting voice recordings

In the beginning, only Morse code could be transmitted. It wasn’t until 1906 that the Canadian physicist Reginald Fessenden worked out how to transmit a recording of a voice. In modern technology, we know his invention as a continuous wave transmitter. This meant the transmitter produced “a continuous train of radiant waves of substantially uniform strength” [5]. On Christmas Eve 1906, Fessenden transmitted a broadcast from Brant Rock, Massachusetts, to ships at sea in the Atlantic. They heard Fessenden playing O Holy Night on the violin, as well as reading from the Bible. This was the first successful audio broadcast by radio.

The Golden Age of radio

When the First World War began, radio technology became a risky business. In the United States, the Navy took control of the majority of radio stations to prevent them becoming potential security breaches [6]. After the war, the Golden Age of radio quickly began. The invention of the superheterodyne receiver in 1920 catalysed the boom in popularity of radio thanks to the improved sound quality it enabled [7].

The first regular entertainment radio programme appeared in the Netherlands in November 1919. The following year, a radio news programme was launched in Detroit, Michigan, shortly followed by the first college radio station at Union College in the state of New York. From this point until the widespread adoption of television in the 1950s, radio revolutionised communication and entertainment around the world.

Radio transmission in the modern era

In the 1990s, wireless communication was behind one of the biggest cultural and social shifts in history. From its humble beginnings in Gugliemo Marconi’s parents’ attic, wireless technology was used in pagers, mobile phones, computer networks, and the internet. Today, we use this technology every single day in a multitude of formats. Every text message, every WiFi connection, and yes – every time you unlock a car with a button on your key, it’s thanks to wireless technology.

This means that today, radio waves are whizzing through the air constantly, all around us. Millions, if not billions, of radio signals are sent every day, carrying all kinds of information to their destination.

Security of radio transmission

As radio transmission became more popular for communication, so too did the technology to intercept the signals. Criminals, and opposing military forces during times of war, aimed to pick up signals sent by others and use the data being transmitted for their own purposes. Over time, radio communication technology advanced to include additional security features designed to prevent such interceptions.

Protecting transmissions with KeeLoq® hopping code

KeeLoq rolling code is one of the methods developed to protect transmitted data. It is also known as hopping code, because it regularly changes the ‘passcode’ required to successfully send and receive a transmission. The transmitter and the receiver must have matching passcodes in order to allow the transmission. Every time a signal is sent, the passcode is changed. Even if a signal is intercepted, its passcode immediately becomes invalid and unusable.

All CDVI transmitters and receivers utilise KeeLoq rolling code to keep transmissions safe. In access control, transmission is certainly an incredibly useful solution. For automatic doors and automatic gates, radio signals can trigger them to open when the user approaches. In listed buildings or sites with glass walls, wireless technology can mean neat and tidy, non-invasive installations.

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