Instruction Manual
20220653 / Rev. C 11
DECODER
(Gating)
Smoothing
Offset
adjust
Filter
(0,6 - 0,75)
sec.
Pulse
with
conv.
Pwr.
Supply
Excitation
2,5 kHz
(Multiplexer)
N
S
Figure 3-1 RFC35 Block diagram
3.2 RFC35N NMEA Compass
The RFC35N is based on the standard RFC35, with a plug-in
NMEA PCB incorporated.
The compass comes with a 15 m cable, open end.
The PCB converts the pwm (pulse width modulated) signal from
the main PCB to NMEA0183 HDG format.
The 2-wire pwm signal is still available for autopilot connection.
Different from a standard RFC35, the NMEA compass has it’s
own microcontroller and memory (EEPROM) where calibration
data and offset adjustment are stored.
Compass calibration can be activated from an IS15 instrument or
other equipment, such as a PC, if a proprietary NMEA sentence
is transmitted to the compass. When the calibration is completed,
the compass transmits a sentence to confirm “Calibration
completed”.
If the RFC35 is connected to equipment that cannot
communicate on NMEA, it can be calibrated the same way as the
obsolete Robertson RFC250 compass. That is; let the boat turn
starboard in a circle until it passes north 3 times.
This procedure must take place within 5 minutes after having
applied power to the compass.
As there will be no “Calibration completed” signal, the only way
to verify a successful calibration is to check it against known
bearings or against the main steering compass providing this is
compensated and correct.
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