User manual: Installation and Operation of Direction Finder System RHOTHETA RT-600 / SAR-DF 517
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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
