Where to Listen

The VHF aeronautical communications band lies between 108.000 MHz and 136.975 MHz.  This frequency spectrum can be divided into a lower and upper range. The lower range between 108.000 MHz and 118.000 MHz is primarily used for navigational aids such as the ILS - Instrument Landing Systems, DME - Distance Measuring Equipment, and VORs - Very High Frequency Omni Range. The lower range offers very little in the way of voice communications, it does however provide someone with a working knowledge of Morse Code the opportunity to identify various beacons. The upper range of the aeronautical band, 118.000 MHz to 136.975 MHz is where the majority of voice communications can be monitored. Communications in the VHF band are transmitted in AM mode and most if not all compatible receivers automatically default to this mode. Frequencies within the aeronautical band are spaced in increments of 25 kHz, as such you will find transmissions at 118.000, 118.025, 118.050 MHz etc.

The UHF aeronautical band is located between 225.000 MHz and 400.000 MHz and is primarily used for military traffic. In the early years the Canadian military was responsible for patrolling the DEW (Distant Early Warning) Line for foreign invasions. As UHF was the only system in use at the time it has become the mainstay. Many commercially available receivers are not capable of tuning this frequency range and therefore this offers some form of security. Air traffic control facilities are equipped to transmit on both the VHF and UHF frequency simultaneously. This method of transmission allows a person whose receiver in unable to tune the UHF frequency the benefit of hearing at least one side of the conversation. The key is to monitor a parallel VHF frequency for the designated UHF frequency.

What you can hear

The frequency(s) you monitor will determine the nature of traffic you will hear. As previously mentioned, frequencies in the lower range of the aeronautical band are mostly occupied by navigational equipment and transmit non voice signals in Morse Code. If you select a frequency in the upper range the air is suddenly filled with conversations between pilots and air traffic controllers, pilots and their company dispatchers, flight service stations, and ATIS broadcasts. Depending on your geographical location it is also possible to hear aircraft under the control of a facility in another Province, or for those living near the Canadian/USA border an American state. Frequencies within the aeronautical band are designated according to their usage. The following frequency allotment chart will give you an idea of where to locate the traffic that most interests you.

When to Listen

There are no rules as to what time of the day is best, however each airport does have it's own peak periods. Based on traffic patterns at Pearson International Airport in Toronto, the busiest times occur between 7 and 9 AM, and 4 to 7 PM. The radio may seem very quiet during the overnight hours at your local airport this however does not necessarily mean there is nothing to hear. Monitoring the enroute (ACC) frequencies can often reward you with traffic from aircraft that have departed from a distant airport and that are overhead on their way to a city many miles away.

What equipment you will need

In order to monitor VHF & UHF aeronautical communications you must have a receiver, more commonly referred to as a scanner, that is capable of tuning between 108.000 to 136.975 MHz and 225.000 to 400.000 MHz respectively. As there are many models to choose from when selecting a receiver the best bet is to first choose one suitable to your budget. Once you are familiar with your new found hobby, purchasing an upgraded radio is an easy transition. Depending on the radio you have purchased the antenna type, if supplied, will vary considerably. This too can be upgraded by purchasing an antenna that performs better for the aeronautical bands. Generally if you live within 40 kilometers of an airport you should be able to hear ground communications, however geographic obstructions such as tall buildings or big hills can hamper your reception. Since VHF & UHF signals are received by line of sight, signals from airborne aircraft tend to be a lot clearer. A good philosophy for optimum antenna performance is "the higher the better". A couple of other useful resources to have while monitoring aeronautical communications would be aviation charts and a base map of your local airfield. A base map of your local airfield will allow you to see and follow the route aircraft use between the runways and parking areas.

The Phonetic Alphabet

During radio transmissions letters and numbers can become difficult to understand and may be confused with one another. To avoid any confusion the Phonetic alphabet is use when pronouncing letters. Numbers too are pronounced slightly different thus eliminating any confusion. As an example, N632PI is pronounced as "November - Six - Tree - Too - Papa - India"

UTC Time

UTC or Coordinated Universal Time is used in aeronautical communications to eliminate confusion between AM and PM. This can be critical especially to flights that cross many time zones. To calculate UTC, convert your local time to the 24 hour clock ex; 0100 = 1 AM, 0200 = 2 AM, 1200 = noon, 1300 = 1 PM, then add 4, 5, 6, or 7 hours for Eastern, Central, Mountain, or Pacific time respectively during daylight savings time. During standard time add 5, 6, 7, and 8 hours to your local 24 hour time.

Altitudes

Taxiway & Runway Numbering

For simplicity taxiways are identified by phonetic names that may consist of either a letter, number, or combination of both. Examples may include, taxiway "Delta", taxiway "Hotel 2". It is more common to find dual designated taxiways at major airports such as Pearson Int'l Airport. Runways are numbered according to their magnetic heading nearest to the ten degree increment. Runway 24 may actually be 242 degrees, however the third digit is always dropped for clarity. Runway numbers are displayed at the approach end of each runway. A single runway would therefore have different numbers at each end of the runway. You'll notice that these numbers are 180 degrees apart, or reciprocals of each other. From the example on the right we have runway 06L/24R. It should be noted that runways in Northern Domestic Airspace are assigned numbers based on true bearings.

Aircraft Callsigns

There are virtually thousands of callsigns used by general, commercial, or military aircraft. Depending on the type and nature of the aircraft these callsigns will vary. The one common denominator to all aircraft registered in Canada is their registration which all begin with the letter "C" then followed by four letters. An example appears in the photo to the right.. Each country has it's own prefix which helps to identify the country of registration.

General aviation and Business Jet aircraft will generally use the aircrafts registration as the callsign. These callsigns are pronounced phonetically over the radio, an example from the photo, "C-FCTV" which is pronounced as "Charlie-Foxtrot-Charlie-Tango-Victor". Once positive identification is established the first two or three letters may be left out to expedite conversation. The last three letters, if available, may be personally requested by individuals or companies to reflect their initials or corporate letters. For example in this photo you'll see the registration carried by the CFTO/CTV news helicopter, note the last three letters in the registration are "CTV ". In some cases the make of the aircraft followed by the last two or three letters or numbers of the registration may be used as the callsign. An example of this may include a "Gulfstream III" aircraft carrying a registration of C-GPJI. The radio callsign in this case would be "Gulfstream Gulf-Papa-Juliet-India, which might then be abbreviated to Juliet-India.

Commercial aircraft, those operated by an airline, will generally use the name of the airline followed by the flight number eg; "Air Canada 856", "First Air 860". Some airlines do however use colourful names in place of the airline's name. A few examples include British Airways, who use the radio callsign "Speedbird", or South African Airways, which use the callsign "Springbok". Listeners will often hear a commercial flight use the term "heavy" in the callsign. The term heavy applies to aircraft that are capable of a takeoff weight of 300,000 lbs or more, examples include B-747, B-767, MD-11 to name a few.

Canadian Armed Forces aircraft use a variety of callsigns depending on the type of aircraft and mission being operated. The callsign "Canforce" followed by a series of numbers usually identifies an aircraft with diplomats or VIP's onboard. Military aircraft on specific missions often use a callsign pertaining to their function such as "Rescue"###. Others may include the "Snowbirds" or "Moose" which are high performance demonstration aircraft.

Another very common callsign suffix heard is "Medevac" which stands for Medical Evacuation. This radio identifier is used by a flight that is responding to a medical emergency for the transport of patients, organ donors, organs, or other urgently needed lifesaving medical materials. Many Provinces operate an Air Ambulance service. A common frequency used by Air Ambulance (Medcom) flights throughout Canada is 129.275 MHz. Pictured on the left is one of the S-76 helicopters (in old colours) operated by Ornge who provide medevac services for the province of Ontario. They use the callsign "Canadian".

Nav Canada operate a fleet of three aircraft that are used for navigational equipment calibration/flight checks. The fleet consists of 2 Canadair CL-600-2B19 aircraft using the callsign NavCan 1 & 2. The third aircraft is a de Havilland Dash 8-102 using the callsign NavCan 3. While performing ILS flight checks at airports throughout Canada, aircrews use 135.850 and 135.950 MHz to communicate with the technical operations crews on the ground.

Airport Firefighting apparatus use the callsign "Red" followed by the vehicle number, ei; Red 1, Red 2, etc.. Many of the airport fire departments in Canada have dedicated radio frequencies in the 460-463 MHz range, others may be found on an 800 MHz trunked radio system that the local airport authority may be using. During an emergency, communications between the flight deck and firefighting crews was often relayed through the local ground control agency, this however has changed. A new national policy has been implemented whereby 122.675 MHz is now available to aircrews and firefighters to communicate directly with one another during an emergency on the ground.

VFR & IFR

Visual Flight Rules, or VFR for short are the minimum weather conditions and distances from clouds that aircraft may operate in without having to file an instrument flight plan. Generally aircraft operating by means of visual reference to the ground are considered VFR. The minimums for VFR flight in Canada are as follows:

Within Control Zones and Aerodrome Traffic Zones

• flight and ground visibility not less than 3 miles
• distance from clouds 500 feet vertically, 1 mile horizontally
• height above surface 500 feet
• In addition to the above, the cloud ceiling must not be less than 1000 feet in a Control Zone

Within Control Areas

• flight visibility 3 miles
• distance from clouds 500 feet vertically, 1 mile horizontally

Uncontrolled Airspace

• at or above 1000 feet surface visibility not less than 1 mile
• distance from clouds 500 feet vertically, 2000 feet horizontally
• below 1000 feet to above the surface, visibility not less than 1 mile and clear of clouds

IFR or Instrument Flight Rules are usually considered to be in effect when the weather is below VFR minimums. IFR flights which include commercial airline traffic are aircraft that are operating by means of reference to the instruments in the cockpit.

Traffic Calls

Air traffic controllers can often be heard advising pilots of other aircraft in their vicinity. An example of a traffic call may sound like this "Air Canada 420, traffic at your three o'clock, 1,000 feet above".

Imagine yourself in the pilots seat and visualize a clock in front of you. 12 o'clock is straight ahead, 3 o'clock in off your right wing, 6 o'clock is directly behind you, and 9 o'clock is off your left wing. With this in mind the pilot of flight 420 would check to the right and 1,000 feet above.

Company Operations

Most of the logistical data required by a flight crew to perform their duties is received during their pre-flight briefing which is conducted in the flight operations room. However as might happen, situations and/or complications develope thereby necessitating the need for an aircrew and company dispatchers to be able to communicate with one another. This is done via the use of private " VHF Company Operations Frequencies". Much of the traffic on these frequencies can seem very routine such as amendments to arrival or departure times, confirmation that arrangements have been made for passengers requiring special needs, or a technical problem with the aircraft warrants discussion with a mechanic. During inclement weather though, these frequencies can come to life with an array of traffic. One example might include details of what plans have been made to re-direct a flight to an alternate destination. All the various types of discussions on these discrete frequencies would be to numerous to list. I do recommend that individuals search between 128.825 and 132.000 MHz for local company operations traffic.

ACARS

ACARS is the acronym for "Aircraft Communications Addressing and Reporting System. This digital datalink system is quickly replacing voice communications used for company operations traffic as mentioned above. One of the true benefits of ACARS is the ability for aircrews and dispatchers to contact one another even though they may not be in direct radio range of each other. The vast network of ACARS transmitters makes sending and receiving messages a convenient and reliable process. Newer aircraft are equipped with sensors that automatically send specific data, for example raising the landing gear triggers the system to automatically transmit a departure message, or setting the parking brake sends the arrival or "At Gate" message.

In order to view ACARS messages you must have the appropriate decoding equipment. These "Digital Decoders" are made by companies such as Universal Radio of Ohio, or Lowe's Electronics of the United Kingdom. For those interested in learning more about ACARS, please visit the ACARS Online website for more detailed information.

Local Area Control | Arrivals | Departures | ACC - Enroute | FSS | ATC Transcript

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