10
•
Signal
The signal section shows the signal strength of the received buoy in logarithmic scale. A
full-scale deflection of the bar graph corresponds with an input signal of -50 dBm or
more, an empty bar graph corresponds with an input signal of -90 dBm or less. For
signals weaker than -90 dBm the audio signal should be used to get an indication of the
signal strength of the input signal.
•
Battery
The battery indication shows the status of the batteries.
indicates full batteries, almost empty batteries.
3.4 Buoy Finder 4A display messages
The following paragraphs describe the behaviour of the receiver and the meaning of the
messages in the
main
part of the display. After power up, the receiver is set to synchronize
mode.
Synchronization
At start-up or after signal loss, the Buoy Finder 4A will try to lock in to a buoy signal. The
synchronization process is necessary to make sure that the receiver is properly aligned to the
RF-signal and to the vector boundaries of the buoy’s data pattern. The synchronization process
is indicated by two messages on the receiver’s display:
“
synchronizing
”
The receiver has lost vector synchronization and is waiting for a valid
sync-word to indicate the beginning of a new frame.
“
checking sync
”
The receiver has reached vector synchronization and is currently
double-checking the vector boundary’s.
Normally, after power up or loss of signal, the receiver will display “
synchronizing
” for some
time and then will display “
checking sync
”. After the Buoy Finder 4A has double checked the
vector synchronization it will search for a GPS position and display the heave. If a valid GPS
position is found, the Buoy Finder 4A will also show this position.
NOTE:
The process of synchronization can take anything between 30 seconds to several minutes.
The time needed to reach frame-synchronization depends on several factors like signal strength,
interference, noise bursts and type of buoy. During the synchronization it is possible that the
message switches several times between “
synchronizing
” and “
checking sync
”.
If synchronization has been established some of the received data will be displayed in the main
part of the display.
3.4.1 Gps messages
The GPS position is displayed in the three messages, one for latitude:
lat:
DDºMM.FFFH
H:
N for northern hemisphere, S for southern hemisphere
DD:
0-90
degrees.
MM:
0-59
minutes
FFF:
0-999
1/1000
minutes.
example:
lat: 52º22.080N