74
3
–
PROCEDURE FOR ELIMINATION OF INTERFERENCE (ONLY FOR FX412)
Frequencie
s used to transmit the differential corrections are situated in the 300 kHz band (long
waves). This frequency band is very sensitive to interference that can be generated by the
electric or mechanical devices on board the vessel. To obtain the best results from your FX412,
we advise that you verify the good reception of the differential signal.
Where interference or electrical noise interferes with DGPS reception, we advise that you carry
out the procedures given below to try to eliminate the problem.
3.
1.
–
VERIFICATION OF DIFFERENTIAL SIGNAL RECEPTION
For this operation only,
ALL
equipment on board must be switched off with the exception of the
FX412 which must be switched on.
From the GENERAL MENU, press key 7 (or select 7–DGPS MENU and to press
Enter
).
Choose and program the frequency and the Baud rate of the station nearest to your position
(see paragraph B.9.1). Read on the left of the screen the reception level of the differential signal
(a good signal = ¾ of the black bargraph) and the error rat
e of received information (it should be
zero = white bargraph). In bottom of the screen read the identification number of the DGPS
station together with its status and the list of satellites corrected.
Note the level of reception of the differential signal as well as the success rate, and proceed to
the following paragraphs.
3.2.
–
DETECTION OF THE INTERFERENCE PRESENT
To see if any equipment causes DGPS interference you need to switch on all electric devices
on board, then start the engines. You must start by switching on one item, waiting for 2 minutes
then checking the DGPS SIGNAL LEVEL & % ERROR received. If there is no change to the
SIGNAL LEVEL & % ERROR, repeat the procedure with the next item. Finally start the
engine(s) and once again check the levels. If there is no variation then interference is not
present and your FX412 installation is perfect. If the SIGNAL LEVEL decreases substantially or
the % ERROR increases substantially, go to paragraph 3.
3.3.
–
DETECTION OF THE NATURE OF INTERFERE
NCE
The best tool is an isolated 12 Volts battery, it permits the detection of the type of interference,
conducted interference, (conducted via the power supply), or radiated interference, (received by
the antenna). Connect the FX412 to the isolated 12 Volt battery (ensure that the ground, the
data output and input are completely disconnected) and repeat the procedure in paragraph 2.
If the interference ceases it is on the power supply, go to the next paragraph 4, if the
interference continue go directl
y to the paragraph 5.
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