An air traffic controller shall communicate with pilots in command of all aircraft in his airspace. In real aviation, all aircraft and all air traffic controllers are equipped with radio transmitters and antennas.
Each radio transmitter uses one unique frequency at a time and performs half duplex communication (this frequency is sometimes also called a radio channel).

The radio transmitter can be tuned to the selected frequency manually by its user. In half-duplex communication, each party can communicate to the other, but not simultaneously; the communication has one direction at a time : ATC to pilot(s), or Pilot to ATC.

The radio spectrum of frequencies is divided into bands with conventional names designated by the International Telecommunications Union (ITU): A frequency band is an interval in the frequency domain, delimited by a lower frequency and an upper frequency. The term may refer to a radio band or an interval of some other spectrum.

The frequency band definition:

Frequency band ITU designation ITU abbreviation
30–300 kHz Low frequency LF
300 kHz – 3 MHz Medium frequency MF
3–30 MHz High frequency HF
30–300 MHz Very high frequency VHF
300 MHz – 3 GHz Ultra high frequency UHF
3–30 GHz Super high frequency SHF

In the real world

In the real world, the pilot uses mainly radio communication in the very high frequency band (VHF) in order to use voice communication.

On oceanic flight, with the long distance involved between ATC and pilots, the High frequency (HF) communication band is selected by using the long range communication property of this frequency.

Example of a VHF/HF communication panel in a 737 aircraft:

Vhf radio.png

Military aircraft can use the ultra high frequency band (UHF). These bands are not simulated in IVAO.

8.33 kHz

The aviation VHF communication band ranges from 118.000 MHz to 136.995 MHz.

The "standard" spacing used to be 25KHz or 0.025 MHz between each channel.

118.000 / 118.025 / 118.050 / 118.075 / 118.100 / 118.125 / 118.150 / 118.175 / 118.200

With traffic increasing, it was necessary to create more channels. It was impossible to assign lower channels, as VOR & ILS uses frequencies from 108.00 to 117.95 MHz. Also it was impossible to assign higher channels, as they are used for satellite communications and military operations.

The solution was to reduce channel spacing from 25MHz to 8.33MHz. Hence, within each 25KHz channel we can have three 8.33KHz channels (25/3=8.33).


Therefore, with 8.33KHz spacing within each channel it gives the following table :

Displayed frequency Real frequency Frequency spacing
118.000 118.0000 25KHz
118.005 118.0000 8.33KHz
118.010 118.0083 8.33KHz
118.015 118.0166 8.33KHz
118.025 118.0250 25KHz
118.030 118.0250 8.33KHz
118.035 118.0333 8.33KHz
118.040 118.0416 8.33KHz
118.050 118.050 25KHz

You may have noticed that frequencies 118.000 and 118.005 use the same real frequency but with a different spacing. If you select on your 8.33 radio frequency 118.000, it will automatically operate as an old 25KHz radio. Now, if you select 118.005 it will operate in 8.33 mode. Only 8.33 receivers tuned on 118.005 will be able to hear you.

The new 8.33 kHz channel width for radio communication frequency is already integrated in the Pilot client and ATC client and the IVAO network servers.

In your cockpit, you must setup only the first 2 digits after the decimal and the 3rd digit is automatically tuned by the system to either a 0 or 5.

The 8.33 kHz spacing channel is mandatory in some countries in upper airspace.

As the IVAO pilot software interface is compatible with 8.33kHz, please add the letter Y to the equipment in your flight plan.

In IVAO network

In the IVAO network, users must not use any real radio transceiver.
  • The use of aeronautic radio transmitters is reserved for real world flights.
  • It is forbidden to use them for any IVAO activities.
In IVAO, radio communications are simulated using communication software:
  • TeamSpeak 2 software for communication using voice
  • IVAO pilot client interface and ATC client interface for communication using text and to obtain ATIS information, METAR, TAF …

In order to make communications more realistic, you can choose the VHF frequency in your cockpit or IVAO Pilot Client interface and the software will do the rest to connect you to the correct channel.

The IVAO Pilot Client interface is an IVAO tool which synchronizes the pilot frequency in the cockpit and the interface with the air traffic controller TeamSpeak channel (if existing). An air traffic controller in IVAO is responsible to tune the frequency of his position in the IVAO ATC software radar software, to create a channel in the selected TeamSpeak server, and to complete his ATIS accordingly in order to perform voice control sessions.

Use of frequency in IVAO for air traffic controller

Before you can control an active position, you must manually set the VHF frequency of your controller position in your IVAO ATC software radar scope. This frequency tuning is not automatic.

This frequency can be taken from:

  • The IVAO database (HQ database or your division database)
  • Real charts if the database was not updated
We advise you not to take any real frequencies you may have heard on a real radio receiver. These frequencies are subject to changes in the functionality of many parameters that IVAO does neither use nor simulate.

How to tune the frequency in ATC Client?

Follow the procedure below:
  • Click on the COM1 tab in the IVAO ATC software COMMbox window
  • Type double bars // followed by the VHF frequency wanted

Example: //130.275

How to tune TeamSpeak for voice communication?

Tuning TeamSpeak does not require any VHF frequency. You create a channel by only using your position name. If you use a frequency value as a channel, the system will not work.

What happens when you open an active position as an air traffic controller?

  1. When connecting to the IVAO network (which is called IVAN) with IVAO ATC software, you must choose a network server and a TeamSpeak server.
  2. Your position is identified by using the ICAO code of your control zone or airfield - for example: ICAO_POS.
  3. The VHF frequency is tuned on IVAO ATC software and sent via IVAO ATC software to the IVAN network to associate your position with the frequency.
  4. On TeamSpeak you are connected as - for example: ICAO_POS
  5. Now create your unique channel on TeamSpeak using your position - for example: ICAO_POS (since two different positions can share the same frequency, you cannot use the frequency in the channel name).
  6. The link between the position and the frequency is created by the ATIS of the position and it is broadcasted in the IVAN network.
  7. When a pilot wants to connect to an air traffic controller, and after tuning to the correct frequency, he receives the ATIS information automatically in the IVAO pilot software interface and IVAO pilot software then tunes TeamSpeak to the correct IVAO ATC channel using the position ICAO_POS.

Use of frequency in IVAO for pilots

If you want to fly on IVAO and you are on the apron of an airfield, you must connect to the IVAO network named IVAN. The first step is to tune IVAO pilot software to UNICOM 122.800MHz as the active frequency.
The 122.800 MHz frequency is the unique worldwide self-announcement air to air frequency for all airfields in IVAO.

This frequency can only be used utilising text for technical and practical reasons.

When you are ready to begin your flight, check in the IVAO pilot software interface if there are any air traffic controllers available in your zone.

Any air traffic controller requires 2 way radio communication contact prior to any movement:

  1. If an Air Traffic Controller is available, set the VHF frequency on the IVAO pilot software as the active frequency. You will receive the ATIS information by text and TeamSpeak will automatically connect to this channel (except if you have deactivated voice mode or the air traffic controller is in text only mode).
  2. If there are no air traffic controllers in your area, you must remain on the Unicom frequency 122.800MHz and perform self-announcement text messages using the scratchpad in the IVAO pilot software interface.

Be aware that when there is any technical problem with TeamSpeak software that does not permit two way voice communication, you shall communicate using the IVAO pilot software scratchpad using text as secondary mode. You are not permitted to ignore the text mode procedure in that case.

See also


  • none


  • VID 150259 - Creation - Wiki integration
  • VID 450012 - Update April 2020


  • 01:59, 23 February 2021


  • This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.


  • The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.