Raymarine GPS navigation User Manual download pdf (Page 51)

As you may remember from reading the basic loran information in the

R~~NAV

508 manual, the secondaries get their numbers by using the first

digit of their normal time delay. On this display you actually see the TDs of

all the loran signals, but the two

“S”

numbers highlighted in the reverse block

characters at the left side are the stations being used to get your Lat./Long

readout. So in the Status page example in the preceeding figure, the

”

1“)

“4”

line and the “6” lines are being received.

SNR Display

You can see a display of the

SNR’s

(signal-to -noise ratio) levels for the

Master and all received secondaries in the SNR column. The SNR level is

important because it affects the quality of the position fix and certainly

acquisition time.

The time required to select the correct cycle of the received loran signal is

directly related to the received strength of the signal (SNR). If the signals are

very weak, it usually takes much longer to “Lock-on” and track the signals

and display your position. The table below shows the general range for SNR

levels vs time of acquisition.

f3NR

Table

SNR LEVEL STATUS

TIME TO LOCK

Good Up to 3 minutes

Fair Up to 7 minutes

15-49

Poor Unpredictable

o- 14

Bad Try the GPS

Track Status

The Track Status numbers appearing in the

right hand column labled

"TRACK" vary

from 0

to 8’s during the acquisition process with an

“8”

indicating that the loran is “Locked-on” and

tracking that particular station.

SIGNALSTATUS LORAN ]

EST

STA

N 42 05.32’

w 071 10.14’

ECD

PRESS CLEAR TO EXIT

When one of the signals disappears or becomes too weak to be tracked, the

corresponding status number may go to

“9“

until the signal is recovered. If

the signal is not recovered within 5 minutes, the signal will be considered

“1ost“

and status number reverts to 0 (re-initiating search).

OPERATION 337

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Raymarine GPS navigation User Manual Page 51

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