Radio & Signals
In 1895, Guglielmo Marconi sent a radio signal across a field in Italy. Within 30 years, voices and music were travelling invisibly through the air across entire continents. We had learned to shout into the void. What we didn't know was that the void was already full of signals.
What radio waves actually are
Radio waves are electromagnetic radiation — the same fundamental phenomenon as visible light, X-rays, and microwaves, just at a much longer wavelength. James Clerk Maxwell predicted their existence mathematically in 1865. Heinrich Hertz proved they were real in 1887. Marconi figured out how to use them to transmit information. The physics was discovered by theorists decades before engineers knew what to build with it.
The universe is full of radio signals
Radio astronomy was discovered by accident in 1931 when Karl Jansky, investigating telephone interference for Bell Labs, found that some of it was coming from the direction of the Milky Way. He had accidentally built a radio telescope. The universe turned out to be broadcasting constantly — stars, pulsars, quasars, galaxies, Jupiter's magnetosphere, and the faint cosmic microwave background all emit radio waves.
AwareStation and SDR
Software-Defined Radio (SDR) replaces the complex hardware of traditional radio receivers with software running on a standard computer. A cheap USB SDR dongle can receive signals across a huge frequency range — from aircraft transponders to weather satellites to Jupiter's radio storms. AwareStation in Doncaster uses two Nooelec SDR dongles and a discone antenna to monitor the radio sky 24 hours a day, feeding data to awareverse.co.uk.
The first 130 years of radio silence
If any civilisation within 130 light years of Earth is listening, they may now be detecting our earliest radio broadcasts. Our radio bubble — the sphere of human signals expanding at the speed of light — currently spans about 260 light years across. In cosmic terms, that is a barely perceptible whisper from a tiny rock. But it is a whisper that has never existed before in the history of this planet.
The hydrogen line at 1420 MHz is one of the most significant frequencies in radio astronomy. Hydrogen is the most abundant element in the universe, and neutral hydrogen atoms naturally emit radio waves at this frequency. It was proposed in 1959 as the most logical frequency for interstellar communication — any civilisation with basic radio astronomy would know it. SETI (Search for Extraterrestrial Intelligence) has monitored this frequency for decades. AwareStation includes hydrogen line monitoring as part of its observation programme.