Honeywell International Inc. RTA-50D Manuale Utente
MAINTENANCE MANUAL
965-1696
(2)
VDL Mode 4 subdivides each 25-kHz channel into periodic slots of 13.33-ms duration to
allow short periodic transmissions from many aircraft. VDL Mode 3 requires each aircraft to
synchronize its TDMA slot timing to that of a ground station. VDL Mode 4 stations synchronize
their TDMA slot timing to UTC derived from a source such as GPS.
allow short periodic transmissions from many aircraft. VDL Mode 3 requires each aircraft to
synchronize its TDMA slot timing to that of a ground station. VDL Mode 4 stations synchronize
their TDMA slot timing to UTC derived from a source such as GPS.
(3)
VDL Mode 4 uses a slot reservation protocol that allows VDL Mode 4 stations to access the
network and assure that ADS-B transmission will not be interfered with, without the need for
coordination through a ground station. The access protocol used by VDL Mode 4 is STDMA.
network and assure that ADS-B transmission will not be interfered with, without the need for
coordination through a ground station. The access protocol used by VDL Mode 4 is STDMA.
(4)
VDL Mode 2 and VDL Mode 3 operate in simplex mode; that is, they operate in either
transmit or receive mode on the same frequency. ADS-B operation over VDL Mode 4,
requires concurrent transmission and reception on two different frequencies. Use of VDL
Mode 4 for both ADS-B surveillance and applications and for data link applications requires
concurrent transmission and reception on three different frequencies. If VDL Mode 4 is used
only for data link communications, transmission and reception on only one frequency at a
time is required. As a result the required applications determine the type of radio required
to support VDL Mode 4.
transmit or receive mode on the same frequency. ADS-B operation over VDL Mode 4,
requires concurrent transmission and reception on two different frequencies. Use of VDL
Mode 4 for both ADS-B surveillance and applications and for data link applications requires
concurrent transmission and reception on three different frequencies. If VDL Mode 4 is used
only for data link communications, transmission and reception on only one frequency at a
time is required. As a result the required applications determine the type of radio required
to support VDL Mode 4.
6.
Theory of Operation (TASK 23-20-59-870-806-A01)
A.
VDR Overview (Subtask 23-20-59-870-018-A01)
(1)
The RTA-50D VDR is an airborne VHF radio whose function is to provide aircraft with
line-of-sight air/ground ATC voice and AOC data communications capability in the 118 to
136.975-MHz VHF frequency band. The RTA-50D VDR is capable of operating in DSB-AM
analog voice mode, VHF ACARS data modes (Mode A and Mode 0), and VDL Mode 2 data
mode.
line-of-sight air/ground ATC voice and AOC data communications capability in the 118 to
136.975-MHz VHF frequency band. The RTA-50D VDR is capable of operating in DSB-AM
analog voice mode, VHF ACARS data modes (Mode A and Mode 0), and VDL Mode 2 data
mode.
(2)
A typical aircraft installation consists of two VDRs dedicated for ATC voice communications
and one VDR for data link communications and back up voice communications. Each VDR
interfaces to its own dedicated VHF blade antenna so that simultaneous operation of all
three VDRs is possible.
and one VDR for data link communications and back up voice communications. Each VDR
interfaces to its own dedicated VHF blade antenna so that simultaneous operation of all
three VDRs is possible.
(3)
Figure 6 shows the interfaces between the RTA-50D VDR and other avionics equipment.
NOTE:
Figure 6 also shows the inputs and outputs that are processed in each of the
modes of operation. Interfaces that apply to typical new aircraft installations are
shown as solid lines. Interfaces that apply to legacy retrofit DSB-AM voice-only
installations that do not require VDL Mode A or VDL Mode 2 functionality are
shown as dashed lines.
modes of operation. Interfaces that apply to typical new aircraft installations are
shown as solid lines. Interfaces that apply to legacy retrofit DSB-AM voice-only
installations that do not require VDL Mode A or VDL Mode 2 functionality are
shown as dashed lines.
EFFECTIVITY
ALL
23-20-59
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1 Mar 2011
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