THE LINK-11 MONITORING SYSTEM
(LMS-11)— The LMS-11 provides the operator and
technician with a means of monitoring the integrity of
the Link-11 net. With the LMS-11, the technician has
a real-time visual display of the link while it is
operating.
The LMS-11 consists of the following
three groups of equipment: the data processing group,
the control/display group, and an accessory group.
The data processing group contains the central
processor and the interfaces required to process the
link audio. It also contains a dual 3.5-inch floppy disk
drive and the power control unit. The control/display
group consists of a color graphics monitor and a
keyboard.
The keyboard provides the operator
interface with the LM-11. The functional keys on
the keyboard are color-coded for ease of operation.
The accessory group consists of the color graphics
printer and the spare parts and supplies for the
LMS-11.
LMS-11 OPERATION AND DISPLAYS— The
LMS-11 has five on-line modes of operation. Each
mode has a unique display screen and allows the
technician to evaluate various parts of the link audio
signal and the link digital data. The five modes are as
follows: LINK MONITOR, NET DISPLAY, PU,
SPECTRUM, and CARRIER SUPPRESSION.
LINK MONITOR MODE— The link monitor
mode provides the technician with a real-time display
of link activity. This allows the technician to monitor
and detect link problems as they occur.
NET DISPLAY— The net display contains the
following two distinct modes of operation: the NET
SUMMARY and a PU HISTORY. The Net Summary
mode presents a summary of quantitative information
about the performance of up to a maximum of 21 PUs
in the net. The PU History mode displays the same
quantitative data for a single PU. This data is updated
each time the selected PU transmits. The most recent
21 transmissions of the specified PU are displayed in
the PU History mode.
PU DISPLAY— The PU display presents detailed
information about the audio signal received from a
specified PU. The information is presented in two bar
graphs and shows the relative power and the phase
error of the received signal.
SPECTRUM DISPLAY— The spectrum display
shows the relative power level of the Link-11 tones
and the noise tones that are the odd harmonics of 55
Hertz. The 605-Hz tone is used as a reference and is
set to 0 dB. The relative power of the data and noise
tones is displayed with respect to this level. In this
mode, the effects of noise can be easily viewed.
CARRIER SUPPRESSION— The
carrier
suppression can only be measured while in Net Sync.
The LMS-11 measures the power of the carrier
frequency and compares it to the power of the 605-Hz
tone.
The carrier suppression can be measured
accurately when the radio is off-tuned by – 500 Hz for
the USB and +500 Hz for the LSB.
EVALUATING THE LINK-11 NET— The
LMS-11 can be a very useful tool in evaluating
Link-11 net operations.
The best way to become
proficient on reading the various screens of the
LMS-11 is through practice.
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