User's Manual

UL-801 Installation Manual
Page 23
23-20-06 15 December 2011
M. VHF Management
The UniLink contains an internal VHF radio for its data communication. UniLink will only
attempt to transmit if the radio has successfully tuned to the selected frequency. VHF
Management requires that UniLink perform the following tasks in order to manage the VHF
air-ground link:
• Acquire a frequency - UniLink acquires a frequency by the Automatic selection method
or a frequency is provided by Autotune or manual crew selection/entry or recall from
previously established frequency from Non Volatile Memory at power up.
• Establish a frequency - UniLink establishes the acquired frequency by transmitting a
downlink block and receiving a necessary Positive Acknowledgment response.
• Maintain the frequency - UniLink maintains the established frequency until signal loss on
the frequency or until subsequent new frequency selection or entry.
The UniLink VHF Communication Status is displayed on the COMM STATUS page and is
explained by the table below.
VHF Media Status Reason
COMM/IDLE
Communications have been established with the ground and datalink
messages can be transmitted over VHF. No data is currently being
transmitted.
COMM/SENDING
A message is currently in the process of being transmitted over VHF and
UniLink is waiting for acknowledgement from the ground.
NOCOMM/NO FREQ
UniLink has not selected a frequency for tuning due to invalid FMS lat/long
or no radio type
NOCOMM/SCANNING
UniLink is automatically selecting a frequency for tuning in current region
with enabled DSP.
NOCOMM/CONNECTING UniLink has sent communication to the ground and is awaiting a reply.
NOCOMM/NO DSP All DSPs have been manually selected OFF.
NOCOMM/VOICE The VDR is in VOICE mode.
NOTE: Does not apply to UL-801 with internal VDR.
NOCOMM/VDR INOP VDR inoperative.
NOCOMM/VDR FAULT VDR is reporting a fault.
NOCOMM/VDR UNAVAIL UniLink has not set the VDR’s protocol state.
NOCOMM/MONITORING UniLink has not detected a viable VDL Mode 2 ground station.
NOCOMM/SUSPEND VHF communications have been suspended by the crew.