ACC (Area Control Center) Communications are given for use in the Air Traffic Controllers of ATHINA AREA CONTROL CENTER , so that it is ensured communication between the civil and Military aircrafts and the ground staff.

These communications become in the VHF band (118-136 MHz) for the civil aircrafts and in the UHF band (225-400 MHz) for the Military aircrafts.

Each sector (Northern, Southern, Eastern, Western)is served with two VHF frequencies ( One for Lower and Higher height separation level and one UHF frequency.

Electronic devices (transceivers) are providing these communications. The transceivers have been installed on the mountains of Hymettus (Athens), (Thassos), Akarnanika (Amfilochia), (Sitia), Spergioli (Rhodes Island) and Monastiri (Messinia). Air Traffic Safety Electronic Engineers of Hellenic Civil Aviation Authority are providing maintenance, repairing and upgrading of these transceivers as well as the interfaces of these communications with Area Control Center, so that Air Traffic Controllers can use them.

For each VHF frequency that is emitted and received, exist two transceivers (Main, Stand by) in regular continuous operation for reserve reasons. Also, a moreover transceiver exists per frequency (Extra Stand by), that is intended for using, in case of one of the above transceivers would be damaged. There are also Main, Standby and Extra standby transceivers for UHF frequencies communications requirements.

In the roofs of buildings or in special pylons they are installed mast antennas that are used by the above transceivers. Change Over and Multicouplers units are using to switch between transmit and receive operations of the transceivers.

Air Traffic Safety Electronic Engineers of Hellenic Civil Aviation Authority, that mans the telecommunications stations, are guarantying the good and continuously operation of transceivers and their antennas, intervening when it needs 24 hours of a day, providing maintenance, repairing and upgrading of ACC communications.

VHF communications are given for use in the Air Traffic Controllers of Tower control (Tower) and approach (Approach) control, so that is ensured the communication between the civil and military flying aircrafts and the the ground staff , at the processes of approach, take off and landing of the aircrafts.

In the big Airports the frequencies of tower and approach are different while Air Traffic Control Communications use the same frequency in smaller areas.

VHF communications are distinguished in the three following categories:

• Tower Control Communications (TWR)
• Approach Control Communications (APP)
• AFIS Communications

Electronic equipments (transceivers) are providing these communications. These equipments have been installed in particular spaces of airport or near to these regions. We use telephone lines, leased lines or microwave links to connect the transceivers with special equipments (Remote Control Units). The place that remote control units installed is selected depending on the space cover of airport. The place that remote control units installed is selected depending on the space cover of airport.

Because the importance of this frequencies, we use two transceivers for each frequency one main and one standby, placed if it is possible in different locations places, that are supplied by the line voltage via UPS and in case of interruption by specifically alternating current Generators. For each frequency a third transceiver exist always, with independent operation (Extra Standby), that is supplied with battery 12V.

Two more transceivers (main-standby) are installed in each airport and serve emergencies of danger cases. The emitted frequency of these transceivers has been established by the ICAO, and it is 121,5 MHz and it is common for all the world airports.

Air Traffic Safety Electronic Engineers of Hellenic Civil Aviation Authority , that mans the airports, are guarantying the good and continuously operation of transceivers and their antennas, intervening when it needs 24 hours of a day, providing maintenance, repairing and upgrading of VHF-UHF Airports Communications.

With communications HF is achieved the communication between the services of ground of various airports (Ground-Ground Communications) or in cases of problematic communications VHF, between aircrafts and services of ground of airports (Ground-Air Communications).

Communications HF are materialised with transmitters and receivers Hf-AM, SSB that are installed in the centres of emission / reception of airports, while they are supported from Air Traffic Safety Electronic Engineers of Hellenic Civil Aviation Authority, that they are guarantying the good and continuously operation of transceivers and their antennas, intervening when it needs 24 hours of a day, providing maintenance, repairing and upgrading of HF communications of the airports. The frequencies of the transmitters and the receivers are common for all the airports and are 3015 KHz and 5638 KHz.

In VOLMET communications becomes continuous emission of weather forecast in frequency VHF 127,8 MHz. These transmitters are installed at ground stations of Hymettus (Athens), Sivri (Thessalonica), Lefkada, and Sitia (Creta), and they are been remoted via leased lines. For VOLMET frequencies are been disposed two transmitters with separate antennas for each ground station, (Main-standby), from which it is permanently in emission main.

ATIS (Automatic Information Service) Communications are ground-air communications and they have to inform the aircrafts pilots that approaches or leaves from the airport, all about prevailing meteorological circumstances, as speed and address of wind, visibility, cloud, temperature, atmospheric pressure e.t.c.

The informations that emits ATIS transmitter are continuous and they are updated each half hour. The Frequency of ATIS communications is 123,4 MHz.

• Transmission Centre of "Nea Smirni"

The Transmission Centre of "Nea Smirni"is found in straight line distance of 5 Km from the old Athens Airport (Area Control Centre) and is used as:

1. HF communications Transmission Centre using by Athens International Airport.

2. Intermediary link station between the old Athens Airport (Area Control Centre) and the telecommunications station of "Hymettus" .The remote of HF transceivers becomes from the Area Control Centre at Hellinikon site using leased lines.

For the link requirements, between the "Nea Smirni" Transmission Center and the "Hymettus" ground telecommunications station has been installed, in the "Nea Smirni" Transmission Centre, Microwave link system station of 86 telephone channels, type FARINON.

This link becomes between "Nea Smirni" - "Hymettus" and no between ACC - "Hymettus" because the ACC have not an optical contact with the "Hymettus" , contrary to the "Nea Smirni". It has been installed one more Remote control unit and one more transmitter VHF that serves ATIS communications.

It has been installed one more Remote control unit and one more transmitter VHF that serves ATIS communications.

The "Nea Smirni" Transmission Centre has a complete laboratorial equipment and is manned from Air Traffic Safety Electronic Engineers of Hellenic Civil Aviation Authority.



• Reception Centre of Krevati

This reception centre is found in straight line distance of 15 Km from the ACC Centre of Hellinikon site and is used as:

1. Reception centre for HF communications using by Athens International Airport.

2. Ground Telecommunications station that have been installed VHF transceivers handled emergency frequencies and serves communications ACC of Athinai Area Control Center.

3. Secondary transmission center for ATIS information emission.

The HF transceivers can remote from the ACC using leased lines.