Furuno LC-90 Mark-II User manual

|S| 0. ; OM-E 4300-QH
OINNERS MANUAL
loran c navigator
MODEL LC-90
FURUNO ELECTRIC CO., LTD.
NISHINOMIYA, JAPAN
8806200KY( 87D)
PftMTEO » JAPM

TABLE OF CONTENTS
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INTRODUCTION
Congratulations on your choice of the Furuno LC-90 Loran-C navigator. We
are confident that you will enjoy many years of operation with this fine piece
of equipment.
For over 30 years Furuno Electric Company has enjoyed an enviable
reputation for quality and reliability throughout the world. This dedication
to excellence is furthered by our extensive global network of agents and
dealers.
The LC-90 Loran-C receiver is just one of many Furuno developments in the
field of navigation. Its compact size and ease of installation and operation
make it suitable for use on a wide variety of vessels.
As with most modern instruments, time and experience are required to reap
maximum benefit from your new receiver. To help you meet this end as
quickly as possible, this manual is laid out in as "user friendly" a manner
as possible. The first section covers Basic level operations and later sections
cover Intermediate and Advanced operations.
This unit is designed and constructed to ensure the user of many years of
trouble-free operation. However, to obtain optimum performance from this
equipment, we ask that you read and follow the recommended procedures for
installation, operation and maintenance. No machine can perform to the
utmost of its ability unless it is installed and maintained properly.
We would appreciate feedback from you, the end-user, about whether we are
achieving our purposes in this manual.
Thank you for considering and purchasing Furuno equipment.
CAUTION
Although your Loran C receiver is capable of providing very accurate
position data, no single navigational device should ever be solely relied
upon. Position information obtained from Loran-C should always be doublé-
checked against other sources such as radar, visual and celestical sightings,
sounding measurements, etc. to verify the reliability of the data.
FEATURES .
SPECIFICATIONS .
ELEMENTARY THEORY
Basic Navigation
How Loran-C Works .
OPERATIONAL OVERVIEW
POWER ON/OFF and DIMMER .
. NUMERIC KEYS .
OPERATING MODE/FUNCTION KEYS .
OTHER KEYS .
SUMMARY OF MODES AND FUNCTIONS
Primary Modes, Data Readouts: .
Primary Modes, Data Entry: ..
Secondary (#) Functions: .
Typical Mode Screens .
Typical Function Screens .
INSTALLATION
GENERAL MOUNTING CONSIDERATIONS .
DETAILED INSTALLATION INSTRUCTIONS
Antenna Coupler unit Installation .
Display Unit Installation .
Power connection .
Ground connection .
TESTING AFTER INITIAL INSTALLATION
HOW TO COMBINE WITH AUXILIARY EQUIPMENT
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BASIC LEVEL OPERATIONS
TURNING THE UNIT ON AND OFF .
INITIALIZING THE NAVIGATOR FOR YOUR OWN GEOGRAPHICAL AREA
Clearing the Memory .
Initializing Latitude/Longitude (Function #1) .
READING SPEED AND COURSE (S/C Mode) .
Manual Entry of Magnetic Variation (Function #4) .
True Bearings (Function #4) .
SETTING THE AVERAGING TIME (Function #3) .
AUTOMATIC ASF (Function #4) .
DIMMER .
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SUMMARY OF BASIC OPERATIONS
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INTERMEDIATE LEVEL OPERATIONS
USING ASF WHEN ENTERING TD'S FOK WAYPOINTS
61
ENTRY OF A POSITION INTO A WAYPOINT
Waypoint Entry by Latitude/Longitude Coordinates (WPT Mode): . 33
Waypoint Entry by TD's (WPT Mode):. 34
Waypoint Entry of Present Position (EVT key in WPT Mode): . 36
Waypoint Entry by Range/Bearing From Present Position (CLC Mode): 37
SELECTING WAYPOINT(S) FOR USE WITH OTHER MODES AND
FUNCTIONS
Selection of a Destination WP from Present Position (NAV Mode): ... 38
Specification of a Pair of Waypoints ("From'’ & "To") (NAV Mode): .. 39
RANGE AND BEARING CALCULATIONS (R/B and CLC Modes)
Simple Range and Bearing from Present Position to a WP (R/B Mode): 39
Range and Bearing Between Two Waypoints (CLC Mode):. 40
CROSS-TRACK ERROR FUNCTION (XTE Mode) .. 41
VELOCITY TO DESTINATION (VTD) AND TIME TO GO (VTD Mode) ... 42
ALARM FUNCTIONS (ALM Mode)
Off-course Alarm . 44
Border Alarm . 44
Arrival Alarm . 45
Anchor Watch . 45
ROUTE FUNCTIONS
Storing a Route (PLN Mode): . 47
Following a Route (NAV Mode): . 48
Temporarily Deselecting a Waypoint in a Route (PLN Mode): . 49
EVENT MEMORY
Storing Present Position into an Event Memory . 50
Storing Present Position into a Waypoint Memory (WPT Mode): 51
CONVERTING COORDINATES (WPT Mode) . 51
ADVANCED LEVEL OPERATIONS
WARNING INDICATORS . 53
SNR Indicator (Function #6) 53
CYC Indicator (Function #6) 54
ECD (Function #6) 54
Deviation (Function #6) 54
Audible SNR (Function #7) 55
BLINK Indicator . 56
Power Failure Indicator . 56
MANUAL CONTROL OF LORAN RECEPTION
Manual Cycle Selection (Function #5) . 56
Manual Notch Filter Setting (Function #9) . 57
MANUAL POSITION OFFSET CORRECTIONS
L/L Corrections (Function #2) 59
TD Corrections (Function #2) 61
MANUAL GRI/SLAVE SELECTION (Function #1) .
TD Gradients: .
Angle of Crossing: .
HOLDING THE TRACKING POINT (Function #7) .
SELECTING OUTPUT DATA FORMAT (Function #3) . ■
TUNING INDICATION (Function #8) . ■
TROUBLESHOOTING
Self-check 1 .
Self-check 2 .
SCHEMATICS
APPENDIX A CHARTS OF VARIOUS LORAN-C CHAINS SHOWING
RECOMMENDED TD PAIRS
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IV

FEATURES
The LC-90 has a large variety of functions, all contained in a rugged die-
cast aluminum case that is corapact enough to fit almost any size of boat.
Sealed-membrane touchpads provide positive, splashproof Control of all
functions displayed on the large five line LCD (Liquid Crystal Display)
display.
Both the touchpads and the LCD display have variable backlighting for
nighttime operation, and touchpad operations are confirmed by an audio tone.
The LC-90 features virtually "hands-off" autornatic operation once it has been
initialized for a specific geographic area, since selection of the proper GRI
and the optimum slave secondaries is autornatic, as is ASF compensation
(Additional Secondary Factor) for accurate Latitude/Longitude readout,
autornatic Magnetic Variation for magnetic bearing readouts, and six autornatic
notch filters to eliminate interference. Each autornatic function however may
be manually overridden if the operator desires.
Entry and readout for all position functions may be by either Latitude and
Longitude or by TD r s (Time Differences) for maximum flexibility.
Navigation functions built into the LC-90 include:
• Position readout in Latitude/Longitude or Time Differences (TD's).
• Speed Made Good and Course Made Good.
• Velocity To Destination and Time To Go to destination.
• Range and Bearing to a waypoint and Range and Bearing from waypoint to
waypoint. Bearing can be either True or Magnetic, with autornatic Magnetic
Variation built-in.
• Cross-Track Error, Direction to steer to get back to courseline, Course
Offset, and Range to destination on one display screen.
• Entry of waypoint by Latitude/Longitude, TD's, by Range/Bearing from
present position, or at Present Position.
• Route Planning and autornatic Route following.
• Alarm limit setting for Cross-Track Error alarm. Border alarm, Arrival
alarm, and Anchor Watch alarm.
• Display of signal parameters: SNR (visual and audible indications), ECD,
tracking point, and interference frequency and level, with six autornatic
notch filters built-in.
• Display of operational parameters: GRI slave selection, ASF or manual
correction factors, auxiliary data output(s), and Event memory contents.
LC-90 SPECIFICATIONS
Receiving Frequency:
Receiver Sensitivity:
Dynamic Range:
Differential Dynamic Range:
Interference Rejection:
Tracking:
Tracking Speed:
Settling Time:
Display Resolution:
Alarm Indications:
Computational Base:
Output Signals to Ext. Equipment:
Ambient Temperature Range:
Power Supply:
Weight:
100 KHz
1 microVolt/m
UO dB
80 dB
Six autornatic notch filters built-
in. The se may be manually operated
if desired.
Master, plus 5 secondaries (max.)
80 kts
5 min. nominal (depends on Loran
signal conditions.)
TD: 0.1 microseconds.
L/L: 0.01 minutes.
Range: 0.01 n.m.
Audible and visible, including Cross
Track Error, Arrival, Border and
Anchor Watch alarms.
WGS-72
Range/Bearing: Great Circle.
Furuno CIF for course plotter,
printer, scanning sonar, color video
sounder; NMEA 0180 simple format for
autopilot; NMEA 0183 complex format
for plotters.
Display Unit: 0 to 50 deg. C.
Ant. Coupler: -30 to 70 deg. C.
10-42 VDC, universal, 9w.
110/220 VAC, 50-60 Hz, with external
rectifier.
Display Unit: 2.3 kg
Antenna Coupler: 0.6 kg
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COMPLETS SETS
Name
Main Unit _
Antenna Coupler
Installation Materials
Accessories _
Spare Parts_
INSTALLATION MATERIALS
3
ELEMENTARY THEORY SECTION
The word "LORAN" is an acronym meaning LOn g RAn g e Navigation. The
basic principles of Loran were developed during World War II, and the
system implemented during that time was known as the Loran A system.
The superior Loran-C system was developed later during the 1960's and
was put into widespread service during the late 1970's.
Loran-C is one of several important radio navigation systems in use by
mariners throughout the world today. Loran-C may be thought of as a
medium-range system since it usually covers out to a maximum of 1200 miles
from the transmitting station.
For very close-in, precision work, portable microwave positioning systems
are often employed by such users as the offshore oil industry, and for
short range medium-accuracy work. Decca navigation systems are used in
some parts of the world.
For transoceanic voyages, Sateliite Navigation and/or Omega receivers are
used to provide the sort of coarse accuracy that is suitable on the open
sea. In - ot her word s, it is rarely necessary to know your position down to
the nearest meter when on an ocean voyage, provided that you are
reasonably certain that you are within the shipping låne and not in any
danger of running aground on some nearby atoll.
The Loran-C system was designed and established to provide excellent
accuracy in the region known as the "Coastal Confluence Zone," or CCZ as
it is often called. This region extends from the shoreline seaward to the
100 fathom curve, or 50 nautical miles, whichever is greater.
Loran-C system accuracy is often capable of providing a reliable fix within
30 meters of one's actual position, but more typically, accuracy of about
100-200 meters is possible throughout the coverage area. However, system
repeatability, that is, the ability to return to the same spot consistently, is
usually on the order of 20-30 meters. Quite often it is even better than
that.
Basic Navigation
The essential idea behind a scheme of positioning on the globe is that any
particular point on the earth's surface can be uniquely described by the
intersection of two lines: Latitude, girdling the earth horizontally
(laterally) and Longitude, girdling the earth vertically.
Examine the section of chart shown next page (Fig. 1) depicting an area
off Yokohama Japan. One can see the parallels of Latitude running East
and West horizontally, and the meridians of Longitude running vertically
North and South. Overprinted on this chart are so-called Loran-C Lines
Of Position or TD's (Time Differences) as they are more commonly known.
(We'll get into why they are called TD’s later; suffice it to say for now
that a Loran-C receiver will give you these numbers and that you can use
these numbers to find your position.)
Note that the TD lines run at a variety of angles with respect to the lines
running North/South or East/West. They are in faet actually curved lines,
segments of hyperbolas, but this is difficult to see on this small section of
4

Fig. 1 Loran-C Chart off Yokohama
chart. These TD lines are labeled with numbers in units of microseconds
on the outer edges of the chart. The spacing between adjacent TD's will
vary depending on the scale of the chart as well as the section of
geography being covered. Don't worry about these details just yet, but
note that in this particular example the spacing between adjacent TD's is
either 100 or 200 microseconds.
Just note that for any one position on the chart (that is, at any one
particular Latitude and Longitude) there is at least one pair of Loran-C
TD's that cross each other. There may in faet be more than one pair of
TD's that cross each other at our one point of interest. Some of them may
give you better accuracy than others. Again, we'll delve in to that in more
detail later.
As an example, let's find a point on the chart and compare the position
both by Latitude/Longitude and by Loran-C TD's. At a Latitude of 33
degrees, 52 minutes North and a Longitude of 139 degrees, 35 minutes East
you should find the Southeast corner of Mikura Jima Island. This position
corresponds to the Crossing of the two TD's lines of 36800 microseconds
and 60600 microseconds. Note that a third TD crosses this position also,
but that the exact line isn't printed on the chart explicitly—it is necessary
to interpolate between lines that actually are printed in order to get this
TD, and .by so doing we would come up with a TD of approximately 17750
microseconds.
Now, let's consider in more detail the way Loran-C actually works.
HOW LORAN-C WORKS
The Loran-C system is a "pulsed" system whose fundamental assumption is
that the speed of propagation of a radio wave is constant anywhere in the
area of coverage of the system. This assumption is actually subject to some
corrections, but we will assume for the sake of this discussion that the
speed of a Loran-C signal is actually constant.
Since distance, time and speed are all related, and since we have assumed
that the speed of the signal is constant, if we can devise some means to
measure the time that it takes for a signal to arrive from a distant
transmitter, we can easily calculate the distance the signal has travelled to
get to us. Thank goodness for modern electronics, for it provides means
for making very precise time measurements, down to the order of tenths of
millionths of seconds.
6

A simple Loran-C system is shown in Fig. 2, consisting of a "master"
transmitting station and two "slave" stations. This is the simplest
configuration used. In practice, most of the chains in the world consist of
three or four slave stations associated with each master. Note that the
lines drawn connecting the master and each of the two slaves are known as
"baselines."
To illustrate the basic idea behind the Loran-C system let us take a simple
case, where the boat with the Loran-C receiver is located on one of the
baselines and is in the middle between the master and the slave. If the
transmitters were both to transmit simultaneously, the time taken for the
signals from the master transmitter to arrive will be the same as that for
the signals from the slave to arrive. In other word s, the difference in
arrival time will be zero.
If the boat is moved so that the time difference of signal arrival from
master and slave is kept constant at zero, then the plot of these movements
will be a straight line halfway between the slave and the master stations.
This line will be perpendicular to the basefine. The line of constant time
difference is known as a Line of Position, or LOP for short.
Other LOP' s can be generated for conditions where the time difference
isn't exactly zero, and these LOP's will form hyperbolas rather than the
straight line in our simple case. (Radio navigation systems such as
Loran-C are often referred to as "hyperbolic navigation" systems for this
reason.)
If the master and its associated slaves were all to transmit simultaneously
on the same frequency, the receiver would not be able to distinguish which
station it was listening to in the resul tin g up roar. The stations therefore
are arranged to transmit in a specific sequence of pulses, with very
precisely defined time delays between the transmissions. So, for our simple
case above where the LOP is in the middle of the baseline, the time
difference is no longer zero, but is some specific value of TU.
The receiver's job is to use the start of reception of the master signal as a
reference time to start its internal stopwatch. When the start of the slave
signal is detected, the receiver in essence stops its internal stopwatch,
notes the time difference, and displays it to the operator as a TD.
In order to determine where one is located on any particular Line of
Position, another LOP is needed to intersect the first one. The Loran-C
receiver thus must track more than one slave at the same time. Most
modern receivers are capable of tracking all slaves available in the chain
simultaneously.
The interval of time between the start of the master transmission, the
series of slave transmissions and the next master transmission that repeats
the whole sequence is called the Group Repetition Interval, or GRI. Each
Loran-C chain in the world has a unique GRI assigned to it, and even
though all Loran-C transmitters work on the same frequency (100 KHz),
they can all be sorted out by GRI.
You will remember that the Time Difference's (TD's) are measured in
microseconds (millionths of a second). Further, the designers of the
Loran-C system have assigned an identifying letter code to each slave
station in a chain. These are called either X, Y, W, or Z.
Now look back at the section of chart in Fig. 1 that shows part of the area
near the coast of Japan. You can now better appreciate why the TD's are
lab el ed as they are. The GRI in the label comes first, then the identifying
code letter, and then the time difference in microseconds.
Your Loran-C receiver is considerably more sophisticated than the simple
TD-only receivers we have been describing here. It is capable of
computing Latitude and Longitude directly from these TD's.
This is a complex calculation, and again the fundamental assumption made is
that the velocity of propagation of the signal is constant, While this is
true for propagation over seawater, the velocity is altered slightly when
the signals travel over land. Over land, the velocity is affected by such
factors as the conductivity of the soil and the features of the terrain.
These effects are all lumped together under the title of "Additional
Secondary Factors," or ASF. These factors cannot be modeled exactly in
the TD to Latitude/Longitude mathematical conversion.
The LC-90 however has TD offsets built-into it, describing deviations from
the ideal grid. The offsets were actually measured at sea. The LC-90 can
automatically take these warpages into account to give more accurate
computation of Latitude and Longitude than can a receiver without this
automatic ASF correction.
Note that the TD grid s on a Loran-C overlaid chart can be shifted when
the chart is printed and thus compensated to take care of actual observed
readings from the field. One should still be careful when using
Latitude/Longitude numbers directly from a Loran-C receiver, especially
when near land since this is where significant error s can occur. (Note
that the charts don't even show Loran-C grids over inland areas because
of the extreme distortions in the lat tices over land.) Also, Loran-C is not
meant to be used in harbors or ports since these are usually surrounded
by land masses.
Well, enough theory for now. Let's get down to how you actually operate
your new receiver. Some advanced concepts and further cautions on the
use (and misuse) of the system will be given later.
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OPERATIONAL OVERVIEW
The LC-90 is basieally a rather simple unit to operate, although at first
glance it may be a lit tle intimidating to someone who has never used a
Loran-C navigator before. However once you get to know what the various
abbreviations mean, the simplicity and logie behind the layout and the design
will become more apparent.
Examine the front panel. You will note that there is a large LCD readout
taking up most of the left-hand side of the front panel, a keyboard on the
right-hand side, and all sorts of abbreviations printed on the panel below the
display. These nine abbreviated labels indieate the various Modes in which
the LC-90 may be operated.
In addition, there are 10 seeondary F u n et ion s which may be called up to do
less-often used operations. These Functions are accessed by use of the [Tj
key, followed by a number from |~0~1 to f~9~l •
The keyboard itself contains twenty-three membrane-sealed touchpad keys,
and is divided roughly into four functional areas, delineated by different
color schemes. A distinctive "beep" is generated to confirm to the user that
something did indeed occur whenever he presses a key.
The functional groupings of the touchpad keys are as follows:
POWER ON/OFF and DIMMER
These three brown keys are located at the top right of the keyboard. When
the operator presses the [PWR| key, the LC-90 is activated. After several
seconds, the display will begin to show sorae activity. It is necessary to
press both the [PWR| and the [OFF] keys simultaneously in order to turn off
power to the unit. This procedure is necessary to prevent unintentional
interruption of power should the user accidentally hit the )PWRj key.
The | DIM | key is used to vary the level of backli g h ting of the display and
keyboard for nighttime operation. There are four l e vel s of backli gh ting
intensity: bright, medium, dim and oif. Each time the |DIM| key is pressed,
the level will change in the above sequence.
NUMERIC KEYS
There are eleven numeric touchpad keys, and these are orange in color. The
keys [O]through [9] are employed to enter all numeric data.
The | + /-1 key is a general purpose key that is used to change from North to
South latitude, or East to West longitude when entering data for Modes or
Functions requiring Latitude/Longitude data, and which is also used to
change default values for many Modes and Functions that can be used either
automatically or manually. This key is also used to turn on/off many
functions.
In each Mode or Function where data may be entered, leading zeroes must be
specified (for ex., waypoint "01" must be entered fully, rather than as "1.")
The LC-90 will reject entries it cannot understand where leading zeroes
haven't been entered. Trailing zeroes needn't however be entered ful ly.
For example, a latitude entry of "37" degrees is just as valid as the full
entry of "370000" degrees.
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OPERATING MODE/FUNCTION SELECTOR KEYS
The four blue keys on the lower left of the keyboard are the Mode selector
keys. The two arrow shaped keys select which one of the nine Mode screens
is in use. Pressing these keys causes the Mode indicator arrow to move
sideways to align itself above the labels for the operating Mode on the panel
beneath the LCD display. The readouts on the LCD itself will change in
accordance with the Mode selected. Pressing the left arrow when the mode
indicator is located at the left-hand edge of the panel will shift the indicator
to the far right-hand Mode. Similarly, when the indicator is at the far right
end, the arrow will shift the indicator to the far right-hand Mode.
The key labeled [#] is used to select one of the ten secondary Functions. It
is first pressed followed by a number from [O] to [9] to a ccces s these
secondary Functions. Note that it isn T t necessary to press the |ENT| key to
activate the Function. The LCD display will changed in accordance with the
secondary Function selected by the operator.
The | TD <-» L/L | key is used to change position data from Latitude/Longitude
format to TD format and vice versa.
OTHER KEYS
At the top left of th e key board there are four brown keys, the [E~VT| , 1 ~CLR|
A and ▼ keys. fEVTI stands for Event, and is used when a position is
to be stored in the Event Memory or Waypoint Memory, or when an external
plotter or printer is connected to the LC-90. The position at the moment this
key is pressed is sent out to the external instrument.
The brown [CLR| key stands for Clear. It is used to clear a number from
the display or to silence the audible alarm. The two arrow shaped keys A
and ▼ are used to select where the data entry cursor will be located on
one of the five lines on the display. The cursor will be indicated by the
flashing of the far left character on the d esired line. Before typing in the
new data, the operator pres s e s th e fCLRl key to clear the line, and af ter
entering new data, the blue [ÉNT| key (standing for Enter) will be pressed.
The cursor will automatically advance to the next line where data may be
entered after the | ENTj key is pressed.
Note that if you acciden t ally type in the wrong data or if you hit the wrong
key, you may hit the [CLR| key, followed by |ENT 1 to retrieve the data
stored previously.
The following list shows a summary of the primary operating Modes, and the
secondary Functions of which the LC-90 is eapable of showing.
SUMMARY OF MODES AND FUNCTIONS
Primary Modes, Data Readouts:
S/C : Speed Made Good and Course Made Good, together with present position
(in L/L or TD's, at the discretion of the operator) and the Route and/or
Way points in use.
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VTP : Velocity To Destination (in knots) and Time to Go (in Hours and
Minutes), again together with present position and Route and/or Waypoints
in use.
R/B : Range (in nautical miles) and Bearing (in degrees Magnetic or True,
at the operator's discretion) from present position to destination waypoint,
again together with present position and Route and /or Waypoints in use.
XTE: Cross-Track Error (in nautical miles off the desired track), with
arrow indicators to show direction of offset and direction to steer to get
back an track. As usual, present position and Route and/or Waypoints in
use are shown. Course offset in degrees and Range to destination
waypoint are display ed as well.
Primary Modes, Data Entry:
NAV : This is the Navigation Mode. The desired Route and/or Waypoint (s)
desired are selected in this Mode. Cross-Track Error with Course offset
and Range and Bearing to the desired waypoint are also displayed.
PLN : This is the Route Planning Mode. The waypoints involved in up to
ten different Route Plans are selected in this mode.
WPT ; This Mode is used to enter position data into a Waypoint. Waypoint
data may be entered or recalled for confirmation either as L/L or as TD's.
CUC : This is the Calculation Mode. Trial rho-rho calculations of Range and
Bearing from waypoint to waypoint may be done here. It is also possible to
Define a waypoint by Range and Bearing from present position in this
Mode.
ALM: This is the Mode where Alarm limits are defined for the Cross-Track
Error alarm, the Border alarm, the Arrival alarm and the Anchor Watch
alarm.
Secondary (#) Functipn:
In each of these function the blue QO key is pressed, followed by a single
number. To leave a secondary Function, hit either the left or right arrow
keys.
#0 = This is the Event Memory Function, where the operator can display the
contents of each event memory.
#J_: This is the Initialization Function. The user enters the approximate
present position, and if he chooses to Disable automatic selection, the GRI
and the slave secondaries for use by the LC-90.
#2 : This is the Position Offset Function. The operator may enter the
amount of delta L/L or delta TD offsets desired for a particular area.
There are nine "pages" of offset information that may be stored in memory.
#3 : This is the Averaging Time Function. The operator may choose the
amount of smoothing time constant to be appiied to the L/L and speed
display. The type of output data available at the rear panel for external
devices such as plotters or printers is specified in this Function as well.
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#4: This is the automatic ASF (Additional Secondary Factor) and automatic
Magnetic Variation Function. Both Functions may be disabled rnanually.
The amount of ASF correction automatically used by the LC-90 in the
present geographic area is displayed. Note that at 0 degrees variation.
True North referenced bearings will be obtained.
#5: This is the Cycle Selection Function. The amount that the tracking
point is ti be slewed manually is entered in this Function.
#6: In this function the SNR (Signal to Noise Ratio) and ECD (Envelope to
Cycle Difference) are displayed. These numbers give the operator an
indication of the quality of the incoming Loran signals. The display shows
which cycle of the Master and two secondary stations the LC-90 is
presently tracking, and shows in addition, the deviation of the internal
reference oscillator from the ideal frequency.
#7: This Function is the SNR Visual/Audio Indicator. It allows the
operator to make trial adjustments for example of the antenna location while
watching the display or listening to the LC-90 buzzer remotely. The
tracking point for the master and the two secondaries is also displayed, as
well as the numerical SNR value for each station.
#8: This is the Tuning Indicator Function. The operator may display the
level of signals, both interfering and desired, from 70 to 130 KHz.
#9 : This is the Notch Filter status Function, where the frequency of each
automatic notch filter may be displayed, and if desired where each of the
six filters may be set manually on desired frequencies. The level of signal
on the frequency of each filter is displayed as well.
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Typieal
Mode
Screens