Antenna coupler and antenna
LINK-11 NET OPERATING MODES The
six modes of Link-11 operation are as follows:
The Net Synchronization mode establishes the
initial time base between the NCS and all
The Net Test mode tests the
connectivity of all units in the net and the operation of
the DTS. The Roll Call mode is the normal mode of
Link-11 operations. The Broadcast mode allows a
single unit to transmit tactical data to all other units
repeatedly. The Short Broadcast mode allows a unit
to broadcast its tactical data once every time the
operator depresses the transmit start switch. Radio
Silence allows a unit to receive Link-11 data, but that
unit will not transmit data.
BUILDING A LINK-11 MESSAGE A
Link-11 message consists of the preamble, the phase
reference frame, and the information segment. The
preamble is five frames long and contains the 605-Hz
Doppler tone and the 2,915-Hz sync tone. The phase
reference frame is one frame and provides a starting
reference for the information segment.
information segment of the Link-11 message contains
control codes and tactical data. Control codes are the
start codes, the stop codes, and the address codes.
LINK-11 MESSAGE FORMATS The format
of a Link-11 message is depends on the mode of
The Roll Call mode consists of the
following three different messages: the call-up
(interrogation) message, the NCS report and call-up
message, and the picket reply message. The call-up
message consists of the preamble, the phase reference
frame, and the address code of the unit being
The NCS report is made up of the
preamble, the phase reference frame, the start code,
the tactical information, the control stop code, and the
address of the next unit. The picket reply message is
comprised of the preamble, the phase reference frame,
the start code, the tactical data, and the picket stop
The Broadcast and Short Broadcast messages are
the same format as a picket reply message. In the
Broadcast mode, one unit repeatedly broadcasts its
tactical data and all other units in the net monitor this
data. In the Short Broadcast mode, the operator must
initiate each transmission of data.
In the Net Synchronization mode, the message is
a continuously broadcast preamble. The Net Test
mode message consists of the preamble, the phase
reference frame, and a preset series of data words that
are repeated until the test is stopped by the operator.
LINK-11 DATA TERMINAL SET (DTS) The
Link-11 data terminal set is the heart of the Link-11
The data terminal set performs the
demodulation, and control functions
required for Link-11 operations.
CORRECTION (EDAC) The DTS is capable of
detecting and correcting single bit errors in received
data. It accomplishes this correction by decoding the
six hamming bits that are added to the 24-bit data
word by the transmitting DTS. When a correction is
made, if there are multiple errors or the DTS is in the
error detect and label mode, the error is designated by
two parity bits added to the 24-bit data word before
the data is sent to the CDS computer.
DTS AUDIO TONE GENERATION AND
CHARACTERISTICS The DTS generates a
16-tone composite audio signal.
(modulates) the 24 data bits into 12 audio tones. Each
tone contains two data bits. Added to these 12 tones
are the three tones containing the six EDAC hamming
bits. A sixteenth tone is used for Doppler correction.
The audio tones are the odd harmonics of 55 Hz. The