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RHOTHETA User Manual RT-800
Page 26 of 192
The 360° display/compass rose stays fixed in this position also
regardless of the “Antenna North Adjustment” setting (s. under
Setup/System).
GPS arrow
The GPS arrow relates to the GPS position. Therefore, this
indication is only possible, if GPS data is available.
This indication can be activated for pointing to GPS coordinates
that were decoded from Cospas-Sarsat messages on the
“Decode” page (gray arrow).
For more information s. chapter 6.3.
Bearing arrow
The bearing arrow is the graphical indication of the bearing value
on the 360° display/compass rose.
The bearing arrow additionally displays the opposite direction on
the compass rose.
The bearing value can be indicated (s. also
):
o
Relative to the North / 0° marking of the antenna
respectively heading of the vessel. This is the case if no
external compass is used.
o
Relative to the magnetic north pole
o
Relative to the true (geographical) north pole
Spread of
bearing
Maximum deviation of unaveraged single bearing values.
Table 5 Bearing page indication
6.1.2 Bearing Operation
Once the bearing frequency and the squelch level are set, the bearing operation starts.
If a signal on the selected operating frequency/channel is received, its level will be indicated
digitally in the range of 0% to 99% in the section for signal level indication besides the bar
graph, which additionally represents the signal level in a graphical way (s. positions 14 and 16
in Fig. 5). The squelch level will then be pictured on the scale of the signal level indication at
the manually (or automatically) adjusted value (s. position 15 in Fig. 5).
The bearing electronics will process data only if the signal level is above the selected
squelch level (= noise suppression)
. Even without a received signal the DF-system may
display a certain signal level
(= noise)
. To avoid distractions from environmental noise
signals, the squelch level must be set above the noise level. For the correct setting of the
squelch level, please pay attention to chapter 6.5.3.
The DF-system detects about 280 bearing values per second. These bearing values might
vary significantly, depending on signal quality (signal strength and modulation). This range of
spread is indicated as a green arc on the 360° display in front of the bearing arrow (s. position
22 in Fig. 5). The smaller the arc, the better the signal quality. If the signal quality
deteriorates, the arc becomes larger.
The bearing electronics process the detected bearing values over a certain time interval using
a sophisticated internal algorithm, which provides a steady and reliable indication of the
bearing value (e.g. the bearing arrow does not react to fast-changing reflections and noise
signals). This averaging procedure produces good bearing results, even if there is a wide
spread of single bearing values.
The bearing arrow represents the
relative bearing value
. This value is always relative to
some fixed point, which could be either heading (e.g., the bow-of-the-vessel direction in the