Once upon a time, terrestrial radio as it later became known, ruled the airwaves. In those days a radio was actually called a ‘Wireless’ because of the magical way it received transmissions through the air. Libbi Gorr from ABC Melbourne Radio still calls it a 'Wireless' and every Saturday morning she affectionately uses the term throughout her entertaining show.
There were two main ways to transmit signals, either AM ‘Amplitude Modulation’ of FM ‘Frequency Modulation’. We won’t bore you with the technicalities but each of these methods had clear advantages and disadvantages. Whilst AM uses the longer wavelengths in the medium wave bands allowing the signal to travel further, the band suffers from interference, particularly in dense urban environments. This means AM is generally mono and poorer in quality but it means people in remote locations can listen to the radio.
FM broadcasts on VHF Band II (88-108MHz), a higher frequency offering improved sound quality to AM, the band is subject to multipath interference and is congested so it limits the ability for radio to expand or offer new features and functionality. So FM offers a higher quality stereo signal but can only be transmitted shorter distances so it is mainly confined to urban areas. Over the years, people have used anything from a simple piece of wire to incredibly elaborate aerials to get the best radio signal possible.
DAB+ (Digital Audio Broadcasting), released in 2007, uses a far more advanced and technically robust transmission system and operates in Australia in VHF Band III 174-230MHz. Like other digital technologies, it uses higher frequencies which work extremely well within the coverage area but have a “cliff edge” drop off at the boundary of reception. DAB+ is both cost effective and spectrum efficient technology, allowing broadcasters to offer their popular analogue stations simulcast in digital quality, and significant choice from new DAB+ only station formats such as kids, dance, sport, urban, chill and smooth. DAB+ uses a robust modulation which is designed for radio reception in mobile environments, such as vehicles and public transport.
These days, AM, FM & DAB+ have all fallen victim to the increasing uptake of Internet Radio which seems to be built into or available on almost every electrical device released in the past decade including phones, computers, amplifiers & receivers and of course network music players. This means the selection of AM/FM/DAB+ Tuners has gone from ‘strong’ to ‘hard to find’ in the last few years.