Rhotheta RT-500-M User manual

User Manual
Installation and Operating
R
RT T- -5 50 00 0- -M M ( (M Ma ar ri in ne e) )
Wideband Precision Direction Finder

RHOTHETA User Manual, Installation and Operating RT-500-M
Page 2 of 75
Edited by:
RHOTHETA Elektronik GmbH
Kemmelpark
Dr.-Ingeborg-Haeckel-Str. 2
82418 Murnau
Germany
Tel.: [phone] - 0
Fax: [phone] - 15
Internet: www.rhotheta.de
E-Mail: [email protected]
Copyright © RHOTHETA Elektronik GmbH
All rights reserved
-Issue: 2017/06/12 [Rev 2.01]
-Display Control Unit: Software Vers. 2.00
-Document-ID: 12-9-1-0002-3-1-61
NOTE:
The manufacturer reserve the right to make modifications at any time and without previous
information of the here described product.

RHOTHETA User Manual, Installation and Operating RT-500-M
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RHOTHETA User Manual, Installation and Operating RT-500-M
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Content
1Safety Instructions ..........................................................................................................8
1.1Legend of Symbols.................................................................................................................................8
1.2Basic Safety Instructions ........................................................................................................................9
2EU Declaration of Conformity......................................................................................... 9
3Use and Characteristics................................................................................................ 10
4Short Description........................................................................................................... 11
4.1Front View.............................................................................................................................................11
4.2Bearing Display (Main Page)................................................................................................................13
4.3Rear View .............................................................................................................................................16
5Operation........................................................................................................................ 17
5.1Bearing Operation.................................................................................................................................17
5.1.1Instruction Fields (flags, errors and warnings).........................................................................19
5.1.2Alarm Function.........................................................................................................................20
5.1.3Function Repeat ......................................................................................................................20
5.1.4Function Clear..........................................................................................................................20
5.1.5Function Channel 16................................................................................................................21
5.1.6Function SAR...........................................................................................................................21
5.1.7Function Scan..........................................................................................................................21
5.2Monitoring Operation ............................................................................................................................22
5.2.1Timing of normal Monitoring Operation ...................................................................................23
5.2.2Timing Monitoring with selected Cospas-Sarsat Main Frequency ..........................................23
5.2.3Monitoring operation with filtering of Emergency Transmitters: ID-Only .................................23
5.3Standby-Operation................................................................................................................................24
5.3.1Standby Mode SAR .................................................................................................................24
5.3.2Standby Mode PLB..................................................................................................................24
5.4Scan-Dialogue ......................................................................................................................................25
5.4.1Fast Channel Scan (only available with unlocked option) .......................................................25
5.4.2Fast Marine Scan.....................................................................................................................26
5.5SAR-Dialogue .......................................................................................................................................28
5.6Cospas-Sarsat Decoding Data Content ...............................................................................................29
6Operating and Adjusting ............................................................................................... 31
6.1Switching on/off resp. Reset.................................................................................................................32
6.2Setting Main Bearing Frequency/Channel............................................................................................33
6.2.1Adjusting Main Bearing Frequency..........................................................................................33
6.2.2Setting a Main Operating Channel ..........................................................................................34
6.3Adjusting the Squelch...........................................................................................................................35
6.3.1Hints for Squelch Level Adjustment.........................................................................................35
6.3.2Manual Adjusting of Squelch Levels........................................................................................36
6.3.3Automatic Adjustment of Squelch Levels ................................................................................37
6.3.4Automatic Squelch...................................................................................................................38
6.4Adjusting Monitoring Operation and ID-only Filtering...........................................................................39

RHOTHETA User Manual, Installation and Operating RT-500-M
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6.5Activating Standby Operation ...............................................................................................................40
6.6Setting Brightness (Dimming)...............................................................................................................41
6.6.1Automatic Adjustment of Brightness of Display and LEDs......................................................42
6.6.2Manual Adjustment of Display and LED Brightness................................................................42
6.6.3Adjustment of Key Illumination (legends) ................................................................................42
6.7Setting the Volume (Volume)................................................................................................................43
6.7.1Muting the Speaker (Mute) ......................................................................................................43
6.7.2Setting Speaker Volume ..........................................................................................................44
6.7.3Functional Test of External Speaker .......................................................................................44
6.8Activating Memory / Band function .......................................................................................................45
6.8.1Recall Frequency/Channel from Storage List..........................................................................45
6.8.2Edit Text (of Frequency/Channel) in Storage List....................................................................46
6.8.3Move a Frequency/Channel within a Storage List...................................................................47
6.8.4Delete a Frequency/Channel in the Storage List.....................................................................47
6.8.5Store a new Frequency/Channel in a Storage List..................................................................48
7Menu (Setup) .................................................................................................................. 49
7.1Menu General .......................................................................................................................................50
7.1.1Audio........................................................................................................................................50
7.2Menu Interface......................................................................................................................................51
7.2.1NMEA Std Sentence................................................................................................................51
7.2.2NMEA Mode.............................................................................................................................51
7.2.3NMEA baud rate ......................................................................................................................52
7.2.4Compass Source .....................................................................................................................52
7.3Menu System........................................................................................................................................53
7.3.1Address-ID ...............................................................................................................................53
7.3.2Antenna Unit ............................................................................................................................53
7.3.3Audio Line Output ....................................................................................................................53
7.3.4Antenna Offset.........................................................................................................................53
7.3.5PS Ram....................................................................................................................................54
7.3.6Monitoring ................................................................................................................................54
7.3.7S/N-Ratio AutoSQL..................................................................................................................54
7.3.8AU-Calibration..........................................................................................................................54
7.3.9BeepTone Decoding ................................................................................................................54
7.3.10CPSS Dialog Time..................................................................................................................54
7.4Menu Service........................................................................................................................................55
7.4.1Monitor .....................................................................................................................................55
7.4.2Password .................................................................................................................................55
7.5Unlocking Setup Settings .....................................................................................................................56
8Interfaces and Installation............................................................................................. 57
8.1Diagram of Interfaces / Connection Plan..............................................................................................57
8.2Power Supply and Optional Connections.............................................................................................58
8.3Antenna Unit (Connecting Cable DCU AU) .....................................................................................60
8.4NMEA Bus ............................................................................................................................................61
8.5Service / Test........................................................................................................................................62
8.6Ground connector.................................................................................................................................62
8.7Guideline for optimal DF antenna position ...........................................................................................63
9Technical Data ...............................................................................................................64
9.1Electrical Characteristics ......................................................................................................................64

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9.2Mechanical Characteristics...................................................................................................................66
9.2.1DCU Dimensions .....................................................................................................................66
9.2.2DCU Mounting Cutout..............................................................................................................67
9.2.3DCU Data.................................................................................................................................67
9.2.4Antenna Unit Dimensions ........................................................................................................68
9.2.5Antenna Unit Mast Flange .......................................................................................................69
9.2.6Technical Data Antenna Unit ...................................................................................................69
10Maintenance and Cleaning............................................................................................ 70
10.1Maintenance .........................................................................................................................................70
10.2Cleaning................................................................................................................................................70
11Product Disposal ........................................................................................................... 71
11.1Disposal within the European Union.....................................................................................................71
11.2Disposal outside the European Union ..................................................................................................71
12Appendix ........................................................................................................................ 72
12.1Error Messages ....................................................................................................................................72
12.2Warnings...............................................................................................................................................72
12.3Frequencies of channels on maritime band .........................................................................................73
12.4List of abbreviation................................................................................................................................74

RHOTHETA User Manual, Installation and Operating RT-500-M
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List of figures
Fig. 1 DCU front view .............................................................................................................11
Fig. 2 Bearing Display ............................................................................................................13
Fig. 3 Rear view......................................................................................................................16
Fig. 4 Bearing operation .........................................................................................................17
Fig. 5 Digital display of bearing value .....................................................................................18
Fig. 6 Last bearing (time, frequency) ......................................................................................18
Fig. 7 Instruction fields............................................................................................................19
Fig. 8 Monitoring operation.....................................................................................................20
Fig. 9 Example active monitoring frequency........................................................................... 22
Fig. 10 Monitoring operation...................................................................................................22
Fig. 11 Example: Timing normal monitoring ...........................................................................23
Fig. 12 Example: Timing Cospas-Sarsat ................................................................................23
Fig. 13 Example: Timing Standby Mode: SAR........................................................................24
Fig. 14 Example: Timing Standby Mode: PLB ........................................................................24
Fig. 15 Scan-Dialogue ............................................................................................................25
Fig. 16 SAR-Dialogue.............................................................................................................28
Fig. 17 Display of Cospas-Sarsat Scanning-Mode .................................................................28
Fig. 18 Cospas-Sarsat data decoding ....................................................................................30
Fig. 19 Operating and adjusting.............................................................................................. 31
Fig. 20 Switch-on system information.....................................................................................32
Fig. 21 Input of main bearing frequency .................................................................................33
Fig. 22 Input of a main bearing channel .................................................................................34
Fig. 23 Adjustment squelch level ............................................................................................35
Fig. 24 Dialogue window: Squelch level adjustment...............................................................36
Fig. 25 Auto-Squelch Marker ..................................................................................................38
Fig. 26 Dialogue window Monitoring settings..........................................................................39
Fig. 27 Activation of Standby operation ..................................................................................40
Fig. 28 Dialogue window Dimming .........................................................................................41
Fig. 29 Automatic dimming .....................................................................................................42
Fig. 30 Manual dimming .........................................................................................................42
Fig. 31 Dialogue window Volume ...........................................................................................43
Fig. 32 Muting the speaker .....................................................................................................43
Fig. 33 Speaker volume..........................................................................................................44
Fig. 34 Speaker functional test ...............................................................................................44
Fig. 35 Dialogue window Memory / Band ...............................................................................45
Fig. 36 Text input window.......................................................................................................46
Fig. 37 Operating Menu Setup (example: Interface / NMEA Standard Sentence) ..................49
Fig. 38 Menu General, table default settings ..........................................................................50
Fig. 39 Menu Interface, table default settings.........................................................................51
Fig. 40 Menu System, table default settings........................................................................... 53
Fig. 41 Menu Service table.....................................................................................................55
Fig. 42 Diagram of interfaces / connection plan......................................................................57
Fig. 43 Necessity of DC/DC-converter.................................................................................... 59
Fig. 44 Connecting cable DCUAU ......................................................................................60
Fig. 45 Example for optimal DF antenna position ...................................................................63
Fig. 46 DCU, mechanical dimensions.....................................................................................66
Fig. 47 DCU, mounting cutout ................................................................................................67
Fig. 48 Antenna Unit, mechanical dimensions........................................................................68
Fig. 49 Antenna Unit, mast flange (mechanical dimensions).................................................. 69

RHOTHETA User Manual, Installation and Operating RT-500-M
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1 Safety Instructions
RHOTHETA Elektronik GmbH is constantly trying to keep the safety standard of the products
up to date and to offer the customers the highest possible level of security.
RHOTHETA products are designed and tested in accordance with the valid safety
regulations. The compliance with these standards is continuously monitored by our quality
assurance system. This product is manufactured in accordance with the EC Certificate of
Conformity, tested and left the factory in perfect technical and safety-relevant condition.
To maintain this condition and to ensure safe operation, the user must pay attention to all
instructions and warnings given. For any questions regarding these safety instructions,
RHOTHETA Elektronik GmbH can be contacted at any time.
The observance of the safety instructions will help to prevent personal injury or damage
caused by all kinds of dangers. This requires that the following safety instructions must be
read carefully and understood before using the product, as well as observed when using the
product. The additional safety instructions such as for protecting persons appear in relevant
parts of the product documentation and must also be paid attention to.
In addition, it is the responsibility of the user to use the product appropriately. The product
RT-500-M, a professional direction finder system may not be used in any way that a person /
thing is injured or damaged.
The use of this product other than its designated purpose or in disregard of the instructions of
the manufacturer is the responsibility of the user. The manufacturer takes no responsibility for
the misuse of the product.
The manufacturer is not liable beyond the scope of legal rules!
This guide is part of the product RT-500-M and is retained throughout the lifetime and to pass
with the product.
1.1 Legend of Symbols
NOTE:
This symbol designates tips or additional notes that must be paid attention to and make work
easier.
ATTENTION:
means that ignoring the instructions may lead to property damage or loss of data.
WARNING:
means that ignoring the instructions, there may a danger to health or life.

RHOTHETA User Manual, Installation and Operating RT-500-M
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1.2 Basic Safety Instructions
ATTENTION:
Read and observe the following instructions, warnings and safety instructions of the
manufacturer!
At all work, the local or national safety and accident prevention regulations must be
observed.
Use only the manufacturer prescribed components and / or use only recommended
material by the manufacturer and do not change this.
Connect only approved accessories kits or additional equipment.
The product may only be opened by authorized service personnel.
The unit voids its type approval on operating with unauthorized modifications on the device
or not the intended use.
2 EU Declaration of Conformity
Hereby RHOTHETA Elektronik GmbH declares that the product RT-500-M is in compliance
with the essential requirements and other relevant provisions of:
Directive 2014/53/EU relating to radio equipment (relevant for RT-500-M AU)
Directive 2014/30/EU relating to electromagnetic compatibility (relevant for RT-500-M
DCU)
Directive 2014/35/EU relating to the making available on the market of electrical
equipment designed for use within certain voltage limits (relevant for RT-500-M DCU)
Directive 2011/65/EU on the restriction of the use of certain hazardous substances in
electrical and electronic equipment (relevant for RT-500-M AU and RT-500-M DCU)
The full text of the Declaration of Conformity can be found at:
http:// www.rhotheta.com/products/rt_500_M

RHOTHETA User Manual, Installation and Operating RT-500-M
Page 10 of 75
3 Use and Characteristics
The DF-system RT-500-M combines a communication direction finder and a SAR (Search
and Rescue) direction finder, thus allowing to bear all coastal and maritime radio stations. If
equipped with an EPIRB (Emergency Position Indicating Radio Beacon), with its help persons
or vessels may be found qickly and safely.
The DF-system RT-500-M allows the bearing of radio signals on 5 different frequency bands
as well as their traditional emergency frequencies in the VHF and UHF range, the common
calling up channel 16 in the maritime radio band and the widely used Cospas-Sarsat
emergency signal. Optionally the whole frequency range 118,000 MHz – 470,000 MHz could
be unlocked!
Frequency Ranges: Standard-Version Optional extended Frequency Range
VHF air band 118,000 MHz - 124,000 MHz 118,000 MHz - 136,992 MHz
VHF marine band 154,000 MHz - 163,000 MHz 137,000 MHz - 224,995 MHz
Maritime channels Channel 00
(Ship / Coast)
- Channel 88
(Ship / Coast)
UHF air band 240,000 MHz - 246,000 MHz 225,000 MHz - 399,975 MHz
Cospas-Sarsat 400,000 MHz - 406,092 MHz
UHF FM band 406,100 MHz - 410,000 MHz 406,100 MHz - 470,000 MHz
Full automatic bearing of emergency signals in the monitoring and standby mode guarantees
additionally a permanent MOB (Man Over Board) surveillance and the auto alert function.
The DF-system consists of two units, the bearing AU (Antenna Unit) and the operating device
DCU (Display Control Unit).
The bearing antenna is a dipole antenna, its housing contains all bearing electronics. Thus
short bearing signal paths with low loss, but also high insensitiveness to external disturbing
fields are achieved. The DF-system is working with the Doppler principle, and by the high
scanning frequency of 3 kHz and clockwise / counterclockwise rotation of the antenna to
compensate running time errors highest precision of the system is achieved.
The indicating and operating system (DCU) represents bearing signals and allows operating
and controlling of the bearing antenna. Additionally external devices can be connected
(speaker, audio / line out, PTT push to talk). Also data in- and export is possible by various
interfaces, particularly the input of compass data by a NMEA- interface.
The DF-system is suitable for stationary surveillance of coastal ship traffic as well as for
mobile use on vessels. AU and DCU are watertight (protection IP 67) and may be used under
extreme and rough conditions.
WARNING: The DF-system RT-500-M is not licensed for primary navigation. It may support
navigation if necessary, but navigation of a vessel may not be based under any
circumstances on data obtained by the DF-system.

RHOTHETA User Manual, Installation and Operating RT-500-M
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4 Short Description
4.1 Front View
Fig. 1 DCU front view
Pos. Designation Function See page
1.
Switching on/off the system, or reset function (when working
permanently) 32
2.
Opens dialogue window for adjustment of brightness of the
TFT-display, of the LEDs and illumination of keys 41
3.
Opens dialogue window for adjustment of external speaker
and mute-function 43
4.
Opens dialogue window for adjustment of the squelch level 35
5.
Opens dialogue window for recalling and storing of own
frequencies and channels 45
6.
Opens dialogue window for setting main bearing frequency /
channel. 33
1
2
3
4
5
6
7 8 9 10 11
12
13
14
15161718

RHOTHETA User Manual, Installation and Operating RT-500-M
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Pos. Designation Function See page
7. TFT-Display
(Thin-Film-Transistor)
Shows present bearing values while bearing,
data content of Cospas-Sarsat
or corresponding dialogues of setting
17
29
31
8.
Software controlled function keys 31
9.
Leaving dialogue or adjusting field without storing changed
parameters 31
10.
Arrow keys enable selection of selection fields
Increasing or decreasing of a value for one step
31
11.
Confirms and stores input or selection
Closes dialogue window
31
12.
(n/a)
13.
Opens dialogue window for setup 49
14.
Numeric keys for direct numeric input of frequency/ channel 31
15. Sensor of brightness
Measures environmental brightness for best automatic
adjustment of brightness of the TFT-display and key
illumination
41
16.
Activates dialogue for adjustment of monitoring / scanning-
mode
with selective filtering of emergency transmitters
and standby operation
22, 39
17.
18.
Indicates input of external compass data, if activated in
setup menu. (If option “UTC Time Base” is installed, the
correct reception of GPS-sentences xxRMC/xxGGA is
indicated as well)
17, 52

RHOTHETA User Manual, Installation and Operating RT-500-M
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4.2 Bearing Display (Main Page)
Pos. Designation Meaning See page
1 Frequency or
channel display
Display of present main bearing frequency
or
display of present main bearing channel
17
2 Display of frequency band Display of frequency band related to present main
bearing frequency/channel 17
3 Monitoring / scanning field Display of selected frequencies/channels in
monitoring/scanning operation 22
4 Instruction fields (Flags)
Display, additional to present adjustments (PTT, mute,
alarm display)
Warnings
Error messages
19
5 Clr (Clear) Clearing of bearing value store 20
6 SAR
Shows SAR-Dialogue
It is used for direct selection of SAR-Freqencies, to start
Cospas-Sarsat-Scanning and to start the Cospas-Sarsat
– Decoding.
28
7
Activation of Marine Scan Mode or Fast Channel Scan
Mode (only with unlocked option “Fast Channel Scan
Mode”)
25
Fig. 2 Bearing Display
1
2
3
4
5 6 8 9
10
11
13
14
15
161718192021
12
7

RHOTHETA User Manual, Installation and Operating RT-500-M
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Pos. Designation Meaning See page
8 CH 16 / 121.5 Instant access to common maritime emergency channel
resp. emergency frequency 121.500 MHz 21
9 Rep (Repeat) Calling up last bearing value 20
10
Monitoring/scanning operation will be continued on next
frequency/channel, if currently no data are received on
present frequency.
22
11
Taking over active scanning frequency as main bearing
frequency (at signal reception only) 22
12
The squelch level of the main bearing
frequency/channel may be adjusted directly by
keys
(only possible if main frequency active; deactivated
during Cospas-Sarsat-Scan)
35
13
Sqelch level of
present
frequency/channel
No signal received (squelch level > signal level)
35
Signal is received and beared (squelch level < signal
level)
No signal received (Auto-Squelch active)
14 Display of signal level
Display of signal level of current frequency/channel
color: cyan no reception
color: red signal reception
17
15 Digital level display Digital indication of signal level of active bearing
frequency/channel 17
16 Relative bearing display Graphic display of relative bearing value relative to
longitudinal axis of antenna 17
17 Spread of bearing Maximum deviation of unaveraged single bearing values 17
18
Compass card
or
360°-display
If compass information available: graphic display of
relative bearing value within compass card with display
of the four cardinal points.
Without compass data: Display of relative bearing value
in 360°-display. (If antenna mounted correctly, the 0°-
value corresponds to moving direction/ longitudinal axis
of vessel)
17
19 Heading Pointer
Direction indicator
Is always in 12 o´clock position and displays present
course if compass information available
17
20 Digital bearing display Display of bearing value as a three-digit number 18

RHOTHETA User Manual, Installation and Operating RT-500-M
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Pos. Designation Meaning See page
21 Direction of reference
Indication of selected reference direction:
Relative Brg bearing relative to longitudinal axis of
antenna
Magnetic Brg Magnetic North (bearing relative to
magnetic North)
True Bearing Geographic North (bearing relative to
geographic North)
18

RHOTHETA User Manual, Installation and Operating RT-500-M
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4.3 Rear View
Fig. 3 Rear view
Pos. Designation Meaning See page
1 Service/testport (PC-RS232) Internal testport for software update 62
2 NMEA bus (RS422/RS232) Connection for input of external compass data
Connection for output of all bearing data 61
3 LAN connector For optional Secondary DCU
4 Antenna connector Connecting DCU and AU 60
5 Source connector
Connection power supply
Connection external speaker
Connection audio/line out
Contacts for alarm relay
Contacts for squelch out
Connection for self bearing suppression (SBS/PTT)
58
6 Ground connector Ground connection of DCU, thread M5 62
7 Type plate
8 Pressure compensation
element
Equipped with a goretex membrane the pressure
compensation element prevents over and
underpressure in the DCU.
3
2
1
4 5
6
78

RHOTHETA User Manual, Installation and Operating RT-500-M
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5 Operation
5.1 Bearing Operation
The display unit of the DF-system RT-
500-M during the bearing operation is the
concentrically arranged TFT-display. All
present bearing data, settings and status
reports are displayed here.
Top left in the display the present main
bearing frequency or, if operating in the
sea band, the present main bearing
channel will be displayed. If a duplex
channel is selected, the reference position
"Ship" for a maritime radio station is
indicated additionally, or "Coast" for a
coastal radio station. The frequency band
related to the present main bearing
frequency/channel is indicated too.
A signal received on the selected operating frequency/channel and its level is indicated
digitally in the range of 0% to 99% in the bearing display and as a bar graph. The display is
not calibrated and serves as a measure of signal strength in quality.
The bearing electronics will process data only, if their 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). In order not to bear these environmental noise signals,
the squelch level is to be set above the noise level. For correct setting of the squelch level,
please pay attention to chapter 6.3.
The DF-system is determining about 280 bearing values per second. These bearing values
may vary significantly, depending on signal quality (that is its signal strength and modulation).
This range of spread is the narrower, the better the signals quality is, respectively wider if the
signals quality is decreasing.
The processing electronics will average the bearing values over a certain time, thus achieving
a rather smoothed display of the bearing value, additionally, this averaging procedure still
produces good bearing results if there´s a wide spread of, e.g. 45%. The relative as well as
the digital bearing values will be put out by the DF-system as averaged values.
The relative bearing value is depicted as an arrow and refers to the longitudinal axis of the
antenna. This corresponds, if mounted correctly, to the vessels longitudinal axis respectively
to the present heading. If compass information via NMEA interface is available, the display
will show the relative bearing value within a compass card indicating the cardinal points. If
no compass data are available, the relative bearing value is shown in a 360°-display.
Fig. 4 Bearing operation

RHOTHETA User Manual, Installation and Operating RT-500-M
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Fig. 5 Digital display of bearing value
The digital bearing display is a 3-digit number, its resolution is 1 degree. Depending on
compass data, the bearing data may be put out digitally with following directions of reference:
Display Direction of reference Meaning
Relative Brg. Relative Bearing relative to longitudinal axis of
antenna
Magnetic Brg. Magnetic North Bearing relative to magnetic North
True Bearing True North Bearing relative to geographic North
After end of reception the last bearing value will be displayed flashing for ca. 5 sec. Then the
bearing display will vanish and the field of the digital bearing display will show the passed
time and the frequency of the last received bearing signal "Last Bearing":
Fig. 6 Last bearing (time, frequency)
After pressing key "Repeat" (see 5.1.3) the last bearing value will be displayed once again.
Digital display of bearing value: 74°
Direction of reference
time since last bearing
frequency of last bearing

RHOTHETA User Manual, Installation and Operating RT-500-M
Page 19 of 75
5.1.1 Instruction Fields (flags, errors and warnings)
When bearing an emergency signal and additional functions are activated or operating
parameters are out of their specified limits, the system will inform you by the means of
instruction fields (flags):
Display Meaning See page
All audio outputs are switched mute 43
Self bearing suppression (SBS) active 57, 58
An emergency signal has been detected. Source, signal
frequency and time since detection will be displayed.
The key Clr will deactivate the warning signal and the alarm relay
output.
After that, if receiving no more emergency signal for more than a
minute, the alarm flag will be cancelled automatically.
20
The system will indicate a warning, if the operating parameters
are close to the tolerable limits, or, if external signals are not
available anymore. The system´s basic functions are not affected
yet, but preventive measures are recommended.
72
An error message will be displayed, if one or more operating
parameters are out of admitted limits, or if the electronics have
recognized a malfunction. In this case the system is not working.
Key Clr deactivates the acoustic warning signal.
72
Fig. 7 Instruction fields

RHOTHETA User Manual, Installation and Operating RT-500-M
Page 20 of 75
5.1.2 Alarm Function
When receiving a signal (signal level above squelch level), it will be examined in the
background if it´s a modulated emergency signal. These emergency signals (ELT =
Emergency Locator Transmitter, PLB, MOB) are modulated with a typical, repeating and
distinct sweeping tone.
Once recognized as an emergency signal, alert will be released. A flashing alarm flag
indicates the signals frequency, it´s type and duration since first reception.
At the same time a special internal warning tone informs you about the reception of the
emergency signal. The alert will last (even after end of signal) until confirmation/deactivation
by the flashing function key Clr (warning signal mute).
After that, if no emergency signal is beared for more than a minute on the recognized
scanning frequency, the alarm flag will be cancelled automatically.
NOTE: The alarm relay exit will be activated equally when recognizing an emergency signal.
Like the internal warning tone the relay exit can be deactivated by pressing key Clr. The alarm
relay exit may be used for an external siren, a MOB GPS function or similar.
5.1.3 Function Repeat
The function Repeat will show once again the last valid bearing value. Pressing the function
key F5 Rep will show, flashing for 3 seconds, the last bearing value with its corresponding
digital signal level.
With an external compass activated (true / magnetic bearing), a vessels change of heading
will be considered automatically for the relative bearing.
ATTENTION: If no external compass activated (relative bearing), the indicated bearing value
corresponds to the vessels heading at the time of the bearing. A change of heading in the
meantime has to be considered.
5.1.4 Function Clear
The function Clr clears the internal bearing value averaging store. The averaging store
enhances bearing accuracy and delivers a useful bearing display even with bad received
Fig. 8 Monitoring operation
active frequenc
y
bearing of the signal
alarm flag if emergenc
y
signal was recognized
deactivates acoustic warning