Rhotheta RT-600 Light User manual

User Manual
Installation and Operating
R
RT T- -6 60 00 0& S SA AR R- -D DF F 5 51 17 7
Wideband Precision Direction Finder
with extended COSPAS-SARSAT range & special scan modes
•Standard Version
•Law Enforcement Version

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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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: [2011/06/14] [Rev 2.03.a]
•Edition valid for DCU with Software [Rev ≥3.20 …]
•Edition valid for AU with Software [Rev ≥3.10 …]
LoJack is a registered trademark of LoJack Corporation.
Note:
The manufacturer reserves the right on making modifications of the product described herein
at any time and without previous information.

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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Index
1GENERAL INFORMATION................................................................................................................................5
1.1 Purpose of use of the direction finder.........................................................................................................5
1.2 Scope of delivery ........................................................................................................................................6
1.3 Important basic adjustments.......................................................................................................................6
2OPERATING ......................................................................................................................................................7
2.1 General Operating Principles......................................................................................................................7
2.1.1 Power-On procedure........................................................................................................................8
2.1.2 Main Pages Selection.......................................................................................................................9
2.1.3 Dimming function..............................................................................................................................9
2.1.4 Squelch Operation..........................................................................................................................10
2.2 Direction Finder Mode...............................................................................................................................12
2.2.1 Operating Elements in Bearing Mode.............................................................................................12
2.2.2 Standard Display in Bearing Mode.................................................................................................13
2.2.3 Special Options in COSPAS-SARSAT Bearing mode....................................................................14
2.2.4 COSPAS-SARSAT Decode Window..............................................................................................15
2.2.5 121.500 MHz bearing Window in COSPAS-SARSAT mode..........................................................16
2.2.6 COSPAS-SARSAT Scan Mode......................................................................................................16
2.2.7 Marine Ship Scan Mode.................................................................................................................17
2.3 Law Enforcement and Medical Operation.................................................................................................18
2.3.1 LoJack Pages.................................................................................................................................18
2.3.2 ETS Pages .....................................................................................................................................20
2.3.3 Med Track Pages ...........................................................................................................................20
2.3.4 Law Enforcement Scan Mode ........................................................................................................20
2.4 Frequency Selection Page........................................................................................................................21
2.4.1 Frequency Selection Page, Standard Version................................................................................21
2.4.2 Frequency Selection Page, Law Enforcement Version..................................................................22
2.5 Memory Page............................................................................................................................................22
2.6 Setup Page...............................................................................................................................................23
3ERROR MESSAGES .......................................................................................................................................25
4INSTALLATION ...............................................................................................................................................26
4.1 Antenna unit..............................................................................................................................................26
4.1.1 Influence of the antenna unit location and the environment on the bearing accuracy....................27
4.2 Display Control Unit ..................................................................................................................................29
4.3 Cable Connection / Wiring........................................................................................................................30
5TECHNICAL DATA..........................................................................................................................................31
5.1 Electric features........................................................................................................................................31
5.2 Interface....................................................................................................................................................32
5.3 Mechanical features..................................................................................................................................33
6APPENDIX .......................................................................................................................................................35
6.1 Frequencies of channels on maritime band..............................................................................................35
6.2 Serial interface data protocol (short description)......................................................................................36
6.2.1 General...........................................................................................................................................36
6.2.2 Serial standard output (protocol description)..................................................................................37
6.2.3 Optional extended serial output (protocol description)...................................................................39
6.2.4 Optional serial input (protocol description).....................................................................................41

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List of figures
Display Control Unit Overview................................................................................................................................. 7
Power-On Screen.................................................................................................................................................... 8
Page Selection........................................................................................................................................................ 9
Dimming Setup........................................................................................................................................................ 9
Five Examples for Squelch operation................................................................................................................... 11
Operational Elements in Bearing Mode ................................................................................................................12
Display in Bearing Mode ....................................................................................................................................... 13
Operational Elements and Display in COSPAS-SARSAT Bearing Mode.............................................................14
COSPAS-SARSAT Decode Window.................................................................................................................... 15
121.500 MHz Bearing Window in COSPAS-SARSAT Mode................................................................................ 16
Display in COSPAS-SARSAT Scan Mode............................................................................................................16
LoJack Bearing Screen......................................................................................................................................... 18
ID-Only Mode Menu Options................................................................................................................................. 18
ID Editing Sub-Page.............................................................................................................................................. 19
ID Only Mode Menu with defined ID...................................................................................................................... 19
AutoSquelch during Med Track Operation............................................................................................................ 20
Frequency Selection Page and Operating Elements............................................................................................ 21
Memory Page........................................................................................................................................................ 22
Accessing Setup Page.......................................................................................................................................... 23
Setup Page ........................................................................................................................................................... 24
Error Message....................................................................................................................................................... 25
Mounting drawing of the antenna.......................................................................................................................... 26
Mounting hole pattern for the display.................................................................................................................... 29
Connecting cable / wiring...................................................................................................................................... 30
Drawing of Display Control Unit ............................................................................................................................ 33
Drawing Antenna Unit ........................................................................................................................................... 34
Timing of serial data.............................................................................................................................................. 36

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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1 General information
RHOTHETA Elektronik GmbH is the developer and manufacturer of the Direction Finder System RT-600.
In the United States of America, the system is marketed under the system designation SAR-DF 517.
1.1 Purpose of use of the direction finder
This modern precision direction finder was mainly developed for professional SAR (search and rescue) and LE
(Law Enforcement) purposes.
There are existing two versions:
•The standard version, which offers the possibility to bear and analyze either traditional emergency
frequencies in the UHF and VHF band, the general distress calling channel 16 of maritime radio and the
common COSPAS/SARSAT emergency signal
•The Law Enforcement version, which offers the possibility to bear the traditional VHF emergency
frequency, the common COSPAS/SARSAT emergency signal and different LE-signals (LoJack, ETS
and Med-track)
The complete COSPAS/SARSAT Frequency range (also future channels) is supported by this direction finder.
For practical use, there is also a very fast scanning mode for detecting any possible COSPAS/SARSAT
frequency within one pulse period (< 400 ms) available.
The excellent bearing results becomes possible due to our newly developed patented antenna concept (small,
robust and wide-banded) and the sophisticated bearing analyzing algorithms, which deliver a quick but
nevertheless steady display.
The direction finder was developed to be used under rough conditions such as mobile use on aircrafts or
vehicles.

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1.2 Scope of delivery
•Display Control Unit
•Antenna Unit (with Receiver and DF-controller)
•Connector set for cable (antenna ⇔display) and
power-supply.
1.3 Important basic adjustments
In order to achieve best use of the direction finder, the user is able to perform several adjustments of
configuration. These adjustments can be set up in the setup menu (refer to chapter Operating / Setup Page).
The most important adjustments are:
•Mounting position (adjustment of downside or upside mounting)
•External (remote) dimming of display
Important: If using the external legends-dimming, the limits of the external analog voltage (min / max.)
have to be adjusted correctly in the direction finder setup menu.
For a description of these adjustments, please refer to chapter Operating / Setup Page.

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2 Operating
Operating the direction finder is deliberately very simple with its clearly arranged layout. Except the upper page
rotary switch and the ON/OFF pushbutton, the function of the operating elements always depends on the active
page. All relevant adjustments can be controlled on the display. Figure 1 shows the general layout of the Display
Control Unit’s surface.
2.1 General Operating Principles
Display Control Unit Overview
(1) >LC Graphic Display< (128 x 64 dots dot-matrix display, dark blue on yellow-green background) showing
all relevant operational information depending upon the selected page.
(2) >Menu< options for rotary and push buttons: If a field with dark background and bright text is shown
below a button or switch, the function described in this field may be selected through the operational
element above or below this menu field. In case of the Page Menu, the active page is high-lighted with
dark background, while the inactive page is in black letters.
(3) >ON/OFF< Push-button to switch on / off the system.
(4) >Volume< Rotary Switch, used, depending on the active page, to adjust the volume of the audio output or
to select frequency values (MHz steps).
(5) >SQL< Rotary Switch, used, depending on the active page, to adjust the squelch function or to select
specific functions on a page depending upon the interactive menu on the display.
(6) >CLR / F1< Push-button. If pushed for a short time, this button activates the function F1 described in the
interactive menu on the display below. If pushed for a longer time (ca. 3 seconds), this button activates the
CLEAR function.
(7) >STORE / F2< Push-Button. If pushed for a short time, this button activates the function F2 described in
the interactive menu on the display below.

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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(8) >Rep / DIM< Push-Button. If pushed for a short time, this button activates the setup of the display
dimming function. If pushed for a longer time (ca. 3 seconds), this button activates the repetition of the last
valid bearing and signal level information.
(9) >Page< Rotary Switch to select displayed main pages (“DF” or “MEM”). Together with the DIM button, it is
used to set the display brightness (dimming function).
(10) >Frequency< Rotary Switch to select frequencies.
2.1.1 Power-On procedure
After switching on the unit through the ON/OFF Push-Button, a start screen is shown on the LC-Display for five
seconds:
Power-On Screen
(1) The upper line is showing the name of the product, RT-600 / SAR-DF 517
(2) The second line is showing the sub-version of the equipment, that means either “LE Version” for the
Law Enforcement version, or “Standard Version” for the standard version.
(3) The fourth line is showing the web address of the manufacturer, RHOTHETA Elektronik GmbH.
(4) The lowest line displays software version and serial number information for the antenna unit and
(5) for the display control unit.
After five seconds, the equipment switches into the operational mode by displaying the last active main page
before having been switched off, that means either the DF (Direction Finder) or the MEM (Memory) page.

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2.1.2 Main Pages Selection
There are two main pages which can be selected:
The DF (Direction Finder) Page is the page in which all relevant operational information is shown, depending on
the kind of signal which shall be received.
The MEM (Memory) Page is the page in which memorized operational frequencies can be modified.
Page Selection
(1) The >Page< rotary switch is used to select the active page.
(2) The active page is highlighted with dark background
(3) The inactive page, which may be selected, is written in dark
letters on bright background.
2.1.3 Dimming function
The background of the LC-graphic display is equipped with a LED-array, whose brightness may be adjusted
continuously (from 5 to 100%). Dimming will be performed in an exponential curve, thus allowing very accurate
adjusting under night-conditions
Dimming Setup
(1) Pressing the >Rep/DIM< button for a short time is activating the
dimming setup mode.
(2) Brightness information, as percentage value from 5 % to 100 % in
steps of 5 % is displayed instead of the “Page” field in the upper right
corner of the display.
(3) The >Page< rotary switch can be used to adjust the display
brightness. Right-hand turn will increase the value in steps of 5
percent, while a left-hand turn will reduce the value in steps of 5
percent.
After ca. 3 seconds of user inactivity, the display falls back into the prior main page. The adjusted brightness of
the display will remain stored after switching off the unit.
Dimming of legends may be performed in two ways, using the internal dimming settings as for the LC-display
itself, or using an external (remote) dimming voltage provided by the aircraft.
Internal dimming (on display unit) of legends:
Internal dimming is always active, if the external dimming input is not connected, or if applied voltage is
below 1 V DC. (Refer to the wiring plan). The legends are dimmed in the same manner as the LC display.
External (remote) dimming of legends:
As soon as there’s a voltage >1 V DC at the dimming input, the brightness of legends is controlled
externally by an analog signal. (Refer to the wiring plan and to the operating/setup-menu description).

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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2.1.4 Squelch Operation
The main challenge in direction finder operations is to only use the signal transmitted by the destination for
calculation of the bearing. Noise and other disturbances shall not cause misleading bearing indications.
In order to prevent the direction finder to calculate bearing results which are mislead due to noise and
disturbances, several means are given:
If a signal can be distinguished from noise and other signals by its message content (e.g. LoJack ID), only
transmissions containing the required message content are used for bearing.
In other cases, the squelch can be used to suppress unwanted weak signals and noise. A squelch level, called
threshold, has to be set by the user or automatically by the system. All signals which have a level below this
threshold value will be ignored. Signals above this level will cause a bearing indication.
As a result, a signal to be used for bearing has to be so much stronger than the noise or disturbing signals that
the receiver can clearly distinguish between wanted and unwanted signals.
The result of this requirement is that the sensitivity is reduced to the level set by the squelch threshold. This
results in a reduced maximum distance to the transmitter.
However, it might be desirable to achieve bearing information even for weakest-possible signals which are very
close to the noise level. In this case, it is possible to reduce the squelch level below the noise level. As soon as
the modulation of a signal can be heard in the loudspeaker, it can be expected that bearing is possible.
If the noise itself is a randomly distributed noise (so-called white noise), and there is no other signal receiver, the
bearing indication itself will be randomly distributed. If the noise is not white noise but a disturbance, bearing will
show to the source of the noise.
If there is a very weak signal “in the noise”, this signal will produce a correct bearing indication thanks to
sophisticated bearing technologies used in the RT-600 system. Fluctuations due to noise will be small even at
low signal levels, however the reaction time of the bearing indication can increase.
To verify if a bearing indication is due to white noise or due to an internal disturbance source, respectively, or if it
is due to a real receive signal, the aircraft should make a slow turn. If the bearing indication is due to an external
signal, e.g. a SAR beacon, the bearing indication has to compensate the changed relative flight angle.
Example: Bearing indication is 30°. The signal is weakly audible in the loudspeaker due to being deep in the
noise. The airplane makes a turn left by 60°. If the bearing indication is not changing to approximately 30°+60°=
90°after a few seconds, the bearing is likely to b e due to noise or internal disturbances off the aircraft.
Note: The weaker a signal is, the longer it will take to change the bearing. Durations around 5 seconds are not
unfamiliar in such cases. Therefore, it is not useful to use this procedure for signals with short transmission
times and low transmit duty cycles, such as COSPAS-SARSAT transmission. The procedure is best suited for
ELT transmission with a continuous signal and still well-suited for ELTs with intermittent transmission (down to
33%).
In cases where pulsed signals are to be received, the receiver is able to decide himself which squelch level is
best-suited for normal operation. In such cases, an automatic squelch is provided. The threshold is automatically
set to a value higher than the calculated noise level. The difference in dB between noise and threshold level can
be defined in the Setup Menu. Refer to the chapter “Setup Page” for details. During automatic squelch operation,
the user has the possibility to force the squelch into manual mode, but has to care about the operational
limitations described in this chapter.
In cases where the Antenna Unit checks signal validity autonomously and without useful possibilities of user
interaction, user interaction is not possible and the squelch purely follows internal rules appropriate to the kind of
received signal.

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Examples of different squelch settings:
Without received signal, the noise level (a) is below the correctly
chosen squelch level (b). The receiver audio output remains quiet,
and no bearing is indicated.
With the same received noise level (a), but wrongly set squelch
level (b), there will be an erroneous, noisy bearing available if
there is no receive signal available at that time.
If the squelch is operating in automatic squelch mode, this is
indicated by a sign “A” (c) above the squelch level marker.
Depending on the SN-Ratio Setup, the squelch level is set slightly
higher than the noise level. Using the SQL rotary switch (1), the
user would be able to force the squelch level to a manual setting.
Automatic setting can be re-entered by setting the manual setting
to < 0 % or > 60 %.
Strong, short receive signals will not modify the squelch level
setting.
Five Examples for Squelch operation
If the squelch functionality is controlled by the system, without user
interactions being allowed, this is indicated by a “X” sign (c) above
the squelch level marker.

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2.2 Direction Finder Mode
Generally, the direction finder mode is used to track bearing information towards a transmitter. It shows all basic
information depending of the kind of signal to be tracked.
Mainly, differences in how information is displayed are related to the information content of tracked signals.
Basic information and basic operational possibilities are applicable for signals with no additional information
content, such as 121.500 MHz sweep-tone modulated SAR beacon signals.
In case of signals with additional information content, such as COSPAS-SARSAT data messages, additional
sub-pages may be activated.
2.2.1 Operating Elements in Bearing Mode
Operational Elements in Bearing Mode
The picture above shows the state of the display while the equipment is operated on the international emergency
frequency 121.500 MHz with an active signal being received.
(1) >FREQUENCY< Rotary switch selecting the active frequency. The last selected frequency remains stored
after switching off/on the device. The selected frequency is shown on the graphic display bottom right.
Above, additional information for the selected frequency is displayed. The use of the rotary switch
activates a sub-page. Please refer to the Frequency Selection section for details.
(2) >VOLUME< Rotary switch to adjust the audio output level. The volume of a linked external speaker or
amplifier can be adjusted in a range from 0 (off) to 99 (maximum loudness). The selected volume is
shown in the bottom left corner of the graphic display. The volume remains stored after switching off/on
the device.
(3) >Squelch Level< adjusts the squelch level. The squelch level has to be above the receiving level without
signal (noise). Only signals above the squelch level are audible in the loudspeaker and used by the
direction finder for bearing indication. The >SQL< rotary switch allows to select the squelch threshold, i.e.
a minimum signal strength of an incoming signal to be processed. The current settings on a signal level
scale from 0 % to 60 % is shown in bright letters on dark background below the SQL rotary switch and as
an arrow beside the signal Strength Bar-Graph.
(4) The >CLR< Push-button is used for erasing the internal bearing value averaging store and the Last Signal
Timer. To activate this function, the push-button has to be hold down for a minimum of circa three
seconds. The sophisticated averaging store increases bearing precision and enables at all an usable
bearing display in case of bad receiving signals (if there is a far away transmitter and/or temporary
complete loss of a receiving signal). Caused by the averaging procedure, a drag error may occur, which

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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might be disturbing the bearing indication after a quick change of course of the aircraft or vehicle. In this
case, the indicated bearing value lags by the real bearing value for about two seconds (for very weak
signals even longer). By pressing this push-button after a quick change of course, the display will show the
new bearing value without drag error. Additionally, the CLR Push-Button is used to activate specific
functions high-lighted in the menu below the button:
(5) >STORE< push-button: Without function except if a special function is high-lighted in the menu line of the
display.
(6) >REPEAT< Push-button, when pressed, showing the last valid bearing value with corresponding receiving
level.
(7) >PAGE< Rotary switch to leave the DF mode in order to switch to the MEMORY (MEM) Page / Mode.
2.2.2 Standard Display in Bearing Mode
Display in Bearing Mode
(1) >Relative Bearing value<, by means of a sophisticated averaging procedure, a steady display is
accomplished, either as graphic display or as text in the range of 0°… 359°. (0°corresponds to bearin g
direct ahead).
(2) >Spread<, maximum deviation of un-averaged bearing values. This is an indicator of bearing quality. The
wider the range between the directions of maximum deviation, the worse the received signal is. As a result
of the excellent averaging procedure, even with a spread of 45°, good bearing results are achieved.
(3) >Receiving level< (field strength) of the signal as a relative percentage value, visualized as bar-graph
indication and as decimal value. Even without a received signal a certain noise level may be displayed.
(4) >Squelch level< (independently adjustable and stored for each frequency). Squelch level is indicated as
marker at the Signal Strength Bar-Graph or as direct relative level value. A usable bearing analysis can
only be achieved if the squelch level is above the noise level (without received signal). If the antenna unit
is placed close a heavily disturbing electronic devices, the squelch level has to be raised, thus making the
direction finder being less sensitive. In receive modes where the squelch level is set automatically, an “A”
above the marker indicates the “Autosquelch” functionality.
(5) >Last Signal< timer showing the time since a signal has been received for the last time (i.e. since a signal
has been stronger than the squelch level). Values are “minutes:seconds”.

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2.2.3 Special Options in COSPAS-SARSAT Bearing mode
Especially for the use together with beacons transmitting a data signal according to COSPAS-SARSAT
specifications in the 406-MHz-Band, special functionalities and pages are being provided.
After selection of a COSPAS/SARSAT Frequency (Refer to the chapter “Frequency selection Page”), the bearing
page provides additional information and operating options.
Operational Elements and Display in COSPAS-SARSAT Bearing Mode
(1) >Auto Squelch< indication, indicating that the squelch level is set automatically to be close to the noise
floor. It is recommended to always use the Auto Squelch during COSPAS-SARSAT operation. This can be
achieved by manually selecting 0 % (lowest possible value) or 60 % (highest possible value) as squelch
level. During COSPAS-SARSAT-Operation, this will force the automatic setting of the level.
(2) >Decode< menu option, allows to open the COSPAS/SARSAT Decode sub-page by shortly pushing the
F1 push-button above the menu option.
(3) >>121.500< menu option. The COSPAS-SARSAT signal in the 406 MHz band is transmitted only every 50
seconds in form of a short data burst of 440 or 520 ms. Approaching the transmitter, it will be received
earlier than the 121.500 MHz continuous signal due to its high transmitter power. However, in a lower
distance to a transmitter, bearing on 121.500 MHz is faster thanks to the continuous or rapidly intermittent
signal. The 121.500 MHz menu option allows a direct switch-over to 121.500 MHz. Direct return back from
121.500 to the COSPAS-SARSAT band is possible from the 121.500 MHz bearing Window in COSPAS-
SARSAT mode. Please refer to the chapter “121.500 MHz bearing Window in COSPAS-SARSAT mode”
for details.
(4) >Frequency range< indication. COSPAS-SARSAT is using a channel spacing of 3 kHz for its beacons.
Due to the internal architecture of the direction finder, it is possible to receive more than one channel in
the same time. Thus, frequency steps of the direction finder are 8.33 kHz instead of 3 kHz. The receive
frequency covered by the current receive frequency setting is shown in the display line above the receive
frequency indication.
Important:
If the exact frequency of the COSPAS-SARSAT beacon is unknown, it is strongly recommended to use
the COSPAS-SARSAT scanning functionality for detecting the correct frequency (Refer to the chapter
“Frequency selection Page” & “COSPAS-SARSAT Scan Mode”)

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2.2.4 COSPAS-SARSAT Decode Window
The COSPAS-SARSAT Decode Window allows decoding incoming COSPAS-SARSAT data messages.
COSPAS-SARSAT Decode Window
(1) >Exit< push button (F1 button) allows to leave the decode window and to go back to the COSPAS-
SARSAT bearing mode window.
(2) >Decode< in the upper right corner of the display indicates that the decode function is activated.
(3) >Country< displays the COSPAS-SARSAT Country Code coded into the received data message.
(4) >Last Signal< time since the last COSPAS-SARSAT message has been received in minutes:seconds
format.
(5) >Position< field showing, in case of location protocols being used by the beacon, the encoded GNSS
position data (latitude / longitude) transmitted by the beacon.
(6) >Range< field showing the range of COSPAS-SARSAT channels covered by the actual receive frequency
setting.
(7) >15-HEX-ID< 15-HEX-ID of the beacon in hexadecimal format.
(8) >Data string< of the bits 25 to 112 of the COSPAS-SARSAT data burst in case of short messages, and
bits 25 to 144 in case of a long message format. The last 8 Hex Values are separated by a blank. Bit- and
Frame-synchronization hex values (Bits 1 to 24) are suppressed to increase the readability of the data
message.
(9) >X< sign to indicate that the Squelch is controlled by the antenna unit for optimum sensitivity. The user
has no access to the Squelch setting.

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2.2.5 121.500 MHz bearing Window in COSPAS-SARSAT mode
While being in the 121.500 MHz bearing window activated through the COSPAS-SARSAT Bearing Mode sub-
page, the bearing window is slightly different to the normal bearing window:
121.500 MHz Bearing Window in COSPAS-SARSAT Mode
Differences are:
(1) >406.xxx< push button (F2 button) allows to switch
back to the last used 406 MHz frequency. This
allows to quickly check on 121.500 MHz if a beacon
can already be received on VHF and, in the case
that this is not possible, to cycle back to 406 MHz
quickly.
(2) >CP-SAR-SAT< indication shows that the actual
page belongs to the COSPAS-SARSAT page
section.
2.2.6 COSPAS-SARSAT Scan Mode
If the COSPAS-SARSAT scan mode has been selected, the COSPAS-SARSAT channels, as selectable
manually from the Frequency Selection Page, are scanned. After reception of a valid COSPAS-SARSAT Signal,
the COSPAS-SARSAT bearing mode is activated. Due to the fast scanning – the complete COSPAS-SARSAT
sub-band is scanned within less than 400 ms – detection of a receivable COSPAS-SARSAT signal is possible
within one COSPAS-SARSAT repetition cycle.
Display in COSPAS-SARSAT Scan Mode
(1) >SCAN< flashing indication notifying the user that the equipment is operating in scan mode.
(2) Frequency display indicating the COSPAS-SARSAT scanning frequency range.
(3) >X< sign showing that squelch settings are controlled autonomously by the receiver.
Scan mode can be left by entering a new frequency through the frequency or memory setup.

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2.2.7 Marine Ship Scan Mode
This chapter only applies for the standard version of the RT-600 / SAR-DF 517.
If the Marine Ship scan mode has been selected marine channels 1 to 88 (156.025 to 157.450 MHz) are
scanned, including frequencies in between. After reception of a valid signal, the bearing mode is activated.
The frequency of latest signal that has been found using the scan mode is automatically transferred to the “AUX”
memory channel.
Scan mode can be left by entering a new frequency through the frequency or memory setup.
In order to prevent the scan to stop on noise signals, it is recommended to start scanning operation with high
squelch settings. Reduce the squelch level in steps until the scan stops on an invalid signal for the first time.
Then increase the squelch level only slightly. This will result in the highest possible scan sensitivity without
reacting on noise source, e.g. resulting from disturbances generated by other equipment on the aircraft.

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2.3 Law Enforcement and Medical Operation
The functions described in this chapter only apply to the law enforcement version of the direction finder
equipment.
Law enforcement direction finders are able to track transmitter for
-LoJack stolen car recovery
-ETS stolen money carrying cases recovery
-Med Track for persons in helpless situations recovery
2.3.1 LoJack Pages
After selecting the LoJack frequency through the Frequency Selection Display, the LoJack bearing window is
displayed.
LoJack Bearing Screen
(1) >Automatic Squelch< indication. It is strongly recommended to operate the receiver with automatic
squelch sensitivity setting in case of LoJack operation. However, manual setup of the Squelch level would
be possible. Please refer to the chapter “Squelch Operation” for details.
(2) >ID Filter< hotkey (F2 push-button): Allows activation of ID-only mode. This filter mode allows receiving
one single LoJack transmitter identified by its ID. The shown text (FILT=OFF) indicates that no filter has
been activated yet.
After activation of the ID-only mode, the user is asked by the system to enter an ID:
ID-Only Mode Menu Options
(1) >EDIT< hotkey (F1 push-button). This button opens the
LoJack ID editing sub-page.
(2) >ID only< indication. The field indicated that the receiver is
operating in the filter mode. By pressing the F2 button, ID-
only mode can be left.
The ID may be entered through the editing sub-page in several ways:

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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ID Editing Sub-Page
(1) >VALUE< Data field showing the last received LoJack ID of any active VLU within receive range. In case
that no LoJack ID has been received, the value field is filled with dashes (“ - - - - - “).
(2) >Value to ID< hotkey (F2 push-button) allows to copy the received LoJack ID in the ID field.
(3) >ID< field showing the LoJack ID which shall be selected. If no LoJack ID has been selected, the ID field
is filled with dashes (“ - - - - - “). Manual entry of data is possible. The position of the ID field which can be
modified manually is high-lighted by dark background and bright values.
(4) >Select< rotary switch, allowing to select which position of the ID field shall be modified manually.
(5) >Value< rotary switch, allowing to modify the currently selected position within the ID field.
(6) >Exit< hotkey (F1 push-button), allowing to switch back to the LoJack bearing window.
If an ID has been selected successfully, the LoJack bearing window indicates the selected Lojack ID and the ID-
only mode. In this case, the squelch is controlled by the antenna unit without possibility of user influence,
indicated by an “X” ahead the squelch level marker. The direction finder will calculate bearing information only
while he receives a transmission with the selected ID, thus the squelch is not necessary and only would reduce
system sensitivity.
ID Only Mode Menu with defined ID
(1) >ID< menu option showing the currently selected ID and
allowing, by pressing the F1 push-button, to re-enter the ID
editing sub-page.
(2) >ID only< menu option showing that currently the ID only
mode is active. By pressing the F2 push-button, the ID-
only mode may be deactivated.

User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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2.3.2 ETS Pages
The Law Enforcement version of the RT-600 system is supporting the tracking of ETS transmitters.
If an ETS frequency has been selected, the bearing window for ETS opens. Its operational use is similar to the
standard bearing window.
2.3.3 Med Track Pages
“Med Track”, patient tracking, allows to track persons wearing a small transmitter helping to recover them e.g. in
cases of disorientation or unconsciousness.
If a medical tracking frequency has been selected, the standard bearing page is slightly modified:
AutoSquelch during Med Track Operation
(1) The squelch level is set automatically, indicated by a letter >A<
above the squelch level marker. It is recommended to leave the
squelch in automatic mode.
(2) To reactivate the automatic squelch mode after unintentional
manual modification of the squelch level, manually increase the
squelch level through the >SQL< rotary switch to the maximum
value (60 %).
There are no special functional options available.
Reception of a signal above squelch level is indicated by an acoustic signal (beep tone).
Med Track frequencies always have to be selected through the MEMORY page, i.e. the receive frequency has to
be a memory channel, selected through the frequency selection page.
2.3.4 Law Enforcement Scan Mode
If the Law Enforcement Scan Mode has been selected, the receiver scans ETS and LoJack frequencies for
signals.
On the LoJack frequency, the receiver is staying receiving for a longer period of time. The scanning criterion is
the reception of a LoJack VLU signal with valid LoJack ID.
On the ETS frequencies, normal manual squelch settings for ETS frequencies are used, and the scan mode
stops as soon as a signal is being received.
Reception of signals, which stop the scan mode, will result in the appropriate bearing page to be activated.
Frequency Application Criterion
Country-Specific LoJack-Frequency LoJack Valid LoJack ID
216.4875 MHz ETS Squelch Level
216.5125 MHz ETS Squelch Level
219.930 MHz ETS Squelch Level
219.960 MHz ETS Squelch Level