Rhotheta RT-300 - Volume: Key 5 < Vol.+ > and 10 < Vol; Common Remark; Selective Squelch: Key 4 < ELT Only; User Manual Bearing System RT

User Manual Bearing System RT-300
Issue: 2017/06/27 [Rev 1.04.c] Page 24 of 79 12-9-1-0013-9-2-0001-3-1-60
Therefore, it is important, to periodically check the squelch adjustment, and if required to
readjust the squelch level in order to acquire highest sensitivity of the bearing system.
NOTE
While bearing emergency transmitters, which are often transmitting very weak signals, it may be
useful to deactivate the squelch function in order to obtain highest sensitivity of the bearing
system. In this case it is important to check continuously if the transmitter is beared and not an
interfering signal. This can be verified by changing the heading, causing a change of the relative
bearing value. If required, actuate the "Clear"-function (see 5.2.10).
5.2.5 Volume: Key 5 < Vol.+ > and 10 < Vol.– >
Pressing key 5 < Vol.+ > respectively key 10 < Vol.- >
in the bearing mode, the window „ADJUST VOLUME“
appears.
Further actuating of key 5 increases continuously and
the volume key 10 decreases the volume.
Bar graph and digital display are indicating the
selected percentage (see Fig. 20) of the maximal
volume.
Speaker signal and external audio output are affected equally (see 6.4.2.2).
5.2.6 „Selective Squelch“: Key 4 < ELT only >
5.2.6.1 Common Remark
The international distress frequency 121,500 MHz is reserved exclusively for emergency
transmissions. That means, transmissions are to be sent only in case of emergency or in order
to prevent an emergency. Airliners, aircrafts or vessels as well as coastal radio stations are
obliged monitoring these frequencies in order to intercept distress calls.
Unfortunately the distress frequencies are misused for entertainment, from our experience
about 4 to 8 times a day. In order to prevent false alarms, the bearing system RT-300 has an
integrated function called “selective squelch”. If activated, all signals not transmitting the
specified sweep tone for emergency transmitters will be suppressed. Depending on the field
strength of the signal, the electronics takes several seconds to analyse the signal. If an
emergency transmission is recognized (e.g. Emergency Locator Transmitter) alarm will be
started. This function can only be activated for frequencies in the airband.
Fig. 20