Airband: The Language of the Skies and Its Evolution

Introduction to Airband

Airband, otherwise known as the aircraft band, represents a collection of frequencies within the VHF radio spectrum. This spectrum is designated for radio communication in civil aviation. Often referred to by names such as VHF, or even phonetically as “Victor”, the airband has a rich history and a crucial role in modern aviation. Different sections of this band are utilized for radionavigational aids and the critical area of air traffic control. Acquiring a license to operate on airband equipment is essential in most nations. This license ensures the operator’s proficiency in various areas including language, procedures, and the nuanced use of the phonetic alphabet.

UKAFG UK Airband Frequency Guide 2022

Spectrum Usage

Antenna Arrays and Their Significance

The VHF airband uses frequencies ranging from 108 to 137 MHz. The lowest 10 MHz, specifically from 108 to 117.95 MHz, has been divided into 200 narrow-band channels each of 50 kHz width. These channels are reserved for crucial navigational aids such as VOR beacons and precision approach systems, like the ILS localizers.

For visualisation, consider the antenna array at Amsterdam Airport Schiphol.

Allocation and Transmission

As of 2012, a majority of nations divide the upper 19 MHz into 760 channels, dedicated to amplitude modulation voice transmissions. These transmissions range from 118 to 136.975 MHz and are spaced at intervals of 25 kHz. Europe is leading the change by dividing these channels further into three, thereby allowing up to 2,280 channels. Numerous channels between 123.100 and 135.950 are allocated in the US for various purposes, from government operations to flight tests and even search and rescue missions. Aircraft cruising at 35,000 ft can typically transmit over a range of 200 miles, given favourable weather conditions.

Icom IC-A25CE (Pro Pack) 8.33KHz/25KHz VHF Com Airband Radio

Other Bands

While airband is primary, aeronautical voice communication isn’t limited to it. There are alternative frequency bands, including satellite voice channels on Inmarsat, Globalstar, or Iridium. These channels often find use in vast oceanic regions or remote areas. Their range often extends over much wider areas, sometimes even globally. For military applications, a dedicated UHF-AM band spanning from 225.0 to 399.95 MHz is in use. This band encompasses air-to-air, air-to-ground, and even air traffic control communications.

Navigational Aids

Radio aeronautical navigation aids (often termed as navaids) operate on different frequencies. Non-directional beacons, for instance, function on the 190–415 kHz and 510–535 kHz bands. The instrument landing system has its range in the UHF spectrum, while marker beacons sit at 75 MHz. Distance measuring equipment, crucial for accurate navigation, uses frequencies from 962 to 1150 MHz.

Channel Spacing and Evolution

The historical journey of channel spacing in airband communication is intriguing. Initially set at 200 kHz until 1947, the spacing has seen consistent reductions to accommodate the growing aviation traffic. This spacing evolution led to the introduction of 760 channels by 1990. The congestion in air traffic in Europe further pushed the boundaries, necessitating the 8.33 kHz channels since 2007 for aircraft flying above certain altitudes.

Modulation and Audio Quality

Worldwide, aircraft communication predominantly employs amplitude modulation. Techniques such as AM and SSB are power-efficient, straightforward, and crucially, compatible with older equipment. Interestingly, the audio quality in airband is shaped by the RF bandwidth utilised. Most transmissions are confined within a bandwidth of 6 kHz to 8 kHz, making it apt for conveying speech effectively.

Digital Radio and its Prospects

The idea of transitioning to digital radios has been floated multiple times. The advantages are manifold, including increased capacity and better resistance to interference. The primary hindrance is the international cooperation required to ensure a seamless switch and the extensive implementation timeline.

Unauthorised Use and its Implications

Transmitting on airband frequencies without an appropriate license is deemed illegal in most countries. Every nation has its regulations, often restricting communications for safety and operational reasons. Listening to these frequencies without a license can also be an offense. However, specific countries, such as the UK, allow for listening as it pertains to navigation and weather-related broadcasts.

The airband, with its intricate history and robust system, serves as the backbone of modern civil aviation communication. As aviation continues to grow and evolve, so will the systems that support it, ensuring safer skies for all.