HOW LORAN-C WORKS
The Loran system
consists of three to six transmitter stations. These
are called a "chain." The letter "M" designates the master station inside
the chain. The other stations in the chain are the secondaries. Their
names are V, W, X, Y, and Z, although
not all chains have five second-
ary stations. The secondary
transmitters are synchronized with the
master which transmits at precise
time intervals. This time interval is
called the Group Repetition Interval (GRI). Each chain has a different
GRI.
The
secondary
stations transmit at precise time intervals after the mas-
ter station transmits. Since these transmitters are located hundreds of
miles
apart,
it takes
a different time for the signals from each transmitter
to reach you. The Loran receiver measures this time difference be-
tween
the master and two of the secondaries. The Z-9500
automatically
chooses the best master-secondary pairs for your location. The time
difference or (TD) is measured in micro-seconds. Plotting the TD on a
chart with Loran-C lines results with your position somewhere on a line
of position (LOP). A line of position is an imaginary line on which the
time
delay
between the master and one of the secondaries is the
same.
In this
example
the boat is located somewhere on the 14605.2 Line Of
Position.
The Loran receiver then measures the time difference between the
master and another secondary. The example on the next page is
31882.8. If
you plot this LOP on a
chart, you'll notice that it crosses the
first line-of-position. Your position
is at the intersection of the two lines.
WAYPT * 2
_____________ LIJAYPT * 3
LIJAYPT * 4
_____________ WAYPT * 5
WAYPT * 6
____________ WAYPT * 7
Enter New Waypoint Position
To save a waypoint other than your present position, first press the
Waypoint
Save
key. The
waypoint save menu appears. Now press the
key next to the "More" label. Finally, press
the
key next to the "New
Waypt. Pos." label. A new menu appears. If you wish to save the
waypoint using latitude/longitude, press
the
key adjacent to the "ENTER
LAT/LONG" label. To save a waypoint using TD's, press the key
adiacent to the "Enter TO's" label. The steps
to save a waypoint are
identical. For this
example, we'll use the
latitude/longitude method. The
screen shown below appears.
Now enter the waypoint location. Remember to add a zero to the
longitude if ft's less than 100 degrees. The screen shown at the top of
the next
page appears
after the last longitude number is entered.
Save Upt
Euiter J
Uaypt 11 1
TDI. :40965.60
TD2 :85920.22
N 32°O0.45'
Id 83°11.33'
Down
Erase
Clear I
Uaypt Lat/Long
N ——°
u———0
II
1)
JC lean
56 81
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