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Today, HFDL is an air/ground data link standard with coverage in virtually every corner of the globe, approximately 168,000,000 square miles (440,000,000 km 2) where aircraft are never out of touch both in the air and on the ground. There are around 15 HF ground stations (HGS) available today, and, like a canopy within a jungle, the stations ...
[citation needed] The two individual audio modulation frequencies and their associated sidebands are 90 and 150 Hz. The DDM for a localizer at the outer extremity of the course sector is 15.5% or an electric current equivalent of 150 microamperes full scale deflection .
In February 1976, work commenced to automate the methods contained in the USAF Stability and Control DATCOM, specifically those contained in sections 4, 5, 6 and 7.The work was performed by the McDonnell Douglas Corporation under contract with the United States Air Force in conjunction with engineers at the Air Force Flight Dynamics Laboratory in Wright-Patterson Air Force Base.
The modulation depth of each 90 Hz and 150 Hz signal changes according to the deviation of the aircraft from the correct position for the aircraft to touchdown on the threshold. The difference between the two signal modulation depths is zero when the aircraft is on the correct course and glidepath on approach to the runway—i.e.
The VHF Data Link or VHF Digital Link (VDL) is a means of sending information between aircraft and ground stations (and in the case of VDL Mode 4, other aircraft) over VHF. Aeronautical VHF data links use the band 117.975–137 MHz assigned by the International Telecommunication Union to Aeronautical mobile (R) service .
Many commercial aircraft use the ARINC 429 standard developed in 1977 for safety-critical applications. ARINC 429 utilizes a unidirectional bus with a single transmitter and up to twenty receivers. A data word consists of 32 bits communicated over a twisted pair cable using the bipolar return-to-zero modulation.
Link 16 is a TDMA-based secure, jam-resistant, high-speed digital data link that operates in the radio frequency band 960–1,215 MHz, allocated in line with the International Telecommunication Union (ITU) Radio regulations to the aeronautical radionavigation service and to the radionavigation satellite service.
Common Data Link (CDL) is a secure U.S. military communication protocol. It was established by the U.S. Department of Defense in 1991 as the military's primary protocol for imagery and signals intelligence. [1] [2] CDL operates within the K u band at data rates up to 274 Mbit/s. CDL allows for full duplex data exchange.