A Guide to Air Band Frequencies

Air band frequencies are a vital part of aviation communication, and understanding them is essential for pilots, air traffic controllers, and anyone interested in aviation.

The air band frequencies range from 108.00 MHz to 135.975 MHz, which is a relatively narrow band.

In the United States, the Federal Communications Commission (FCC) regulates air band frequencies, ensuring that they are used efficiently and safely.

There are two main types of air band frequencies: VHF (Very High Frequency) and UHF (Ultra High Frequency), with VHF being the most commonly used.

Check this out: Why Is the Height of a Vhf Radio Important

Air band frequencies are used for communication between aircraft and air traffic control. The VHF frequencies range from 118 to 137 MHz.

Some VHF frequencies are allocated for emergency use, such as 121.500 MHz, which is the international emergency frequency. Another emergency frequency is 123.100 MHz, used for search and rescue operations.

The VHF frequencies are also used for air-to-air communication. For example, 122.750 MHz is the official fixed wing air-to-air frequency, while 123.400 MHz and 123.450 MHz are used for air-to-air "fingers" communication.

You might enjoy: Emergency Radio

Here's a list of some common VHF frequencies:

These frequencies are used for various purposes, including air-to-air communication, search and rescue operations, and emergency communication.

A fresh viewpoint: Air-to-ground Communication

Frequency allocation is a critical aspect of air band frequencies. It's like a big puzzle, where each frequency has a specific purpose and user group.

The Federal Aviation Administration (FAA) has allocated specific frequencies for various uses, including air traffic control (ATC), government services, and emergency services. For instance, 121.500 MHz is designated as an emergency frequency, also known as the "Guard 121.5 MHz".

Here's a breakdown of some key frequencies and their uses:

It's worth noting that frequency allocation can vary depending on the region and country. It's essential to check with local authorities for specific frequency allocations and regulations.

You might like: S Band

The VHF Allocation - 118-137 MHz band is a crucial part of air traffic control. It's used for various purposes, including ATC, Gov AWOS/ASOS, and Emergency Frequency (Guard).

The band is allocated as follows: 118.000 MHz to 121.400 MHz is used for ATC, while 121.425 MHz to 121.450 MHz is reserved for Gov AWOS/ASOS. 121.475 MHz is a band protection frequency for 121.500 MHz, which is the Emergency Frequency (Guard).

There are also specific frequencies allocated for SAR ELT Location Training (121.775 MHz), Aviation Support (121.950 MHz and 123.300 MHz), and FSS Private Aircraft Advisory (122.075 MHz to 122.675 MHz).

Here's a breakdown of the frequencies in the band:

The band also includes frequencies allocated for specific purposes, such as SAR ELT Location Training (121.775 MHz), Aviation Support (121.950 MHz and 123.300 MHz), and FSS Private Aircraft Advisory (122.075 MHz to 122.675 MHz).

In the UK, military airfields have specific frequencies allocated to them. The frequencies for these airfields can vary greatly.

Lossiemouth, a Royal Air Force base in Scotland, has its own set of frequencies. These frequencies are used for communication and other purposes.

Little Rissington, another Royal Air Force base, also has its own frequencies. The frequencies for this base are different from those of Lossiemount.

Some airfields, like Cosford, have frequencies that are used for specific purposes, such as communication with other bases. These frequencies are usually designated for that purpose.

Lakenheath, a US Air Force base, has frequencies that are used for its Havequick system. This system is used for communication and other purposes.

The Valley airfield, which is also a Royal Air Force base, has its own frequencies. These frequencies are used for communication and other purposes.

Coningsby, a Royal Air Force base, has frequencies that are used for its communication systems. These frequencies are usually designated for that purpose.

Colerne, another Royal Air Force base, has frequencies that are similar to those of Coningsby. The frequencies for this base are used for communication and other purposes.

Cranwell, a Royal Air Force base, has frequencies that are used for its communication systems. These frequencies are usually designated for that purpose.

Chetwynd, a Royal Air Force base, has frequencies that are used for its communication systems. These frequencies are usually designated for that purpose.

Upavon, a Royal Air Force base, has frequencies that are used for its communication systems. These frequencies are usually designated for that purpose.

Here are some of the UK military airfields and their frequencies:

Aircraft communication is a crucial aspect of air band frequencies, and it's essential to understand how it works.

Control towers use specific VHF sub-bands for communication, including 118.000 MHz to 121.400 MHz, 121.600 MHz to 121.925 MHz, 123.600 MHz to 128.800 MHz, and 132.025 MHz to 135.975 MHz.

These frequencies are designated for control towers, which use them to communicate with aircraft.

The Aircraft Communications Addressing and Reporting System (ACARS) also plays a significant role in aircraft communication, using frequencies such as 131.72500, 129.35000, and 130.87500.

These frequencies are used for sending messages to and from commercial airlines' aircraft, and they're designated for specific purposes like base frequency, en route, and terminal communication.

Here's a list of some of the ACARS frequencies and their purposes:

These frequencies are just a few examples of the many used in aircraft communication, and it's essential to understand their purposes to ensure safe and efficient air travel.

Air band frequencies operate on a specific range of frequencies, typically between 118.0 and 135.975 MHz. This range is divided into several sub-bands.

The most common air band frequency is 121.5 MHz, also known as the universal emergency frequency. This frequency is used for emergency communications and is often the first choice for pilots in distress.

Air band frequencies can be further categorized into different types, including VOR frequencies, which are used for navigation, and non-directional beacon frequencies, which are used for navigation and communication.

On a similar theme: Emergency Position-indicating Radiobeacon

Channel spacing was originally 200 kHz until 1947, providing 70 channels from 118 to 132 MHz.

The channel spacing was reduced to 100 kHz in 1947, which increased the number of channels available. This change allowed for more efficient use of the airband.

In 1954, the channel spacing was split again to 50 kHz, and the upper limit was extended to 135.95 MHz, resulting in 360 channels. The addition of frequencies between 136.000 and 136.975 MHz in 1990 added 760 channels in total.

The introduction of 8.33 kHz channel spacing in 2007 required all aircraft flying above FL195 to have communication equipment for this channel spacing. This change allowed for even more efficient use of the airband.

The 8.33 kHz channel spacing resulted in a 6-digit channel numbering scheme, where the 8.33 kHz channel designators differ from the actual frequency. For example, channel 118.010 tunes the frequency 118.0083 MHz.

The emergency communication channel 121.5 MHz is the only channel that retains 100 kHz channel spacing in the US.

Modulation is a crucial aspect of frequency properties, and it's used in aircraft communications radio operations worldwide.

Aircraft communications radio operations predominantly use amplitude modulation, specifically A3E double sideband with full carrier on VHF, and J3E single sideband with suppressed carrier on HF.

This method is simple, power-efficient, and compatible with legacy equipment, making it a reliable choice.

Amplitude modulation permits stronger stations to override weaker or interfering stations, which is beneficial in noisy environments.

The capture effect found in FM is not a concern with AM and SSB, allowing for more effective communication.

Even if a pilot is transmitting, a control tower can "talk over" that transmission and other aircraft will hear a somewhat garbled mixture of both transmissions.

This is a result of the heterodyne effect, which is not evident in FM systems.

Alternative analog modulation schemes, such as the "CLIMAX" multi-carrier system and offset carrier techniques, are under discussion to improve spectrum utilization.

You might like: Cell Phone Fm Radio

The audio quality in airband communication is limited by the RF bandwidth used.

In the newer channel spacing scheme, the largest bandwidth of an airband channel is 8.33 kHz.

This limited bandwidth restricts the highest possible audio frequency to 4.166 kHz.

Most airband voice transmissions don't actually reach these limits, instead, they're contained within a 6 kHz to 8 kHz bandwidth.

The upper audio frequency in these transmissions is typically around 3 kHz to 4 kHz.

This frequency range is sufficient to convey speech, despite being lower than the top of the human hearing range.

Frequency abbreviations can be a bit tricky to understand, but don't worry, I've got you covered.

Ground frequencies are often abbreviated by assuming the "121" prefix, so if the frequency is 121.600, it can be shortened to ".6" or "point six".

If you're reading back a frequency that ends in 5, you can omit the last digit, like in 132.225, which can be read back as "132.22" or "one-three-two point two-two".

In VHF ATC frequencies, the leading "1" is often assumed, so 123.050 can be shortened to "23.05" or "two-three point zero-five".

Omitting the "point" is also common, especially when combining the last two conventions, like in 118.675, which can be shortened to "1867" or "eighteen-sixty seven".

In the airband, the original channel spacing for voice communication was 200 kHz until 1947.

This provided 70 channels from 118 to 132 MHz, with some radios also offering receive-only coverage below 118 MHz for a total of 90 channels.

The 200 kHz channel spacing was later reduced to 100 kHz in 1947, then to 50 kHz in 1954, and finally to 25 kHz in 1972.

The 25 kHz channel spacing allowed for 720 usable channels and was used until the introduction of 8.33 kHz channels in the ICAO European region.

In 2007, all aircraft flying above FL195 were required to have communication equipment for 8.33 kHz channels, resulting in a 6-digit channel numbering scheme.

The 8.33 kHz channel designators differ from the actual frequency, for example, channel 118.010 tunes the frequency 118.0083 MHz.

Outside of Europe, 8.33 kHz channels are permitted in many countries but not widely used as of 2021.

The emergency communication channel 121.5 MHz is the only channel that retains 100 kHz channel spacing in the US.

Frequency Management is crucial for efficient air traffic control and communication. The VHF airband uses frequencies between 108 and 137 MHz.

In many countries, the upper 19 MHz of this band is divided into 760 channels for amplitude modulation voice transmissions, spaced 25 kHz apart. This allows for a large number of channels to be used simultaneously.

Aircraft flying at cruise altitude can transmit signals up to 200 miles away in good weather conditions, which is important to consider when managing frequency usage.

The VHF airband uses frequencies between 108 and 137 MHz, with 200 narrow-band channels of 50 kHz reserved for navigational aids such as VOR beacons and precision approach systems.

These channels are crucial for safe navigation and communication in aviation.

The lowest 10 MHz of the band is split into 200 narrow-band channels, while the upper 19 MHz is divided into channels for amplitude modulation voice transmissions.

Most countries divide the upper 19 MHz into 760 channels, but in Europe, it's becoming common to further divide those channels into three, potentially permitting 2,280 channels.

Some channels between 123.100 and 135.950 are available in the US to other users such as government agencies, commercial company advisory, search and rescue, military aircraft, glider and ballooning air-to-ground, flight test and national aviation authority use.

A typical transmission range of an aircraft flying at cruise altitude is about 200 mi (322 km) in good weather conditions.

Worth a look: Are Public Safety Frequencies Narrow Band

In most countries, it's illegal to transmit on airband frequencies without a suitable license. This includes the US, where aircraft stations are "licensed by rule".

Listening to airband frequencies without a license is also an offense in some countries.

However, in certain countries like the UK, it's permissible to listen to airband frequencies, as it's covered under navigational and weather-related transmissions.