THE MPX GENERATOR
14.2.5
Audio Preset Manager and Alarm:
This section has two sections, called “On Air Audio Preset Change”, which show the preset
channel currently broadcasting (whether this is the factory setting or a customised one),
while the ”External Preset Change” section shows which preset channel is broadcast when
an external command is received. The external command which "switches" the preset
channel broadcasting is inputted at
GPIn-2.
Whenever this
GPIn -2
is closed, the Preset Audio channel is switched over. To render this
function unavailable, select
Disable
.
The "Alarm On" section shows which conditions are recognised as alarms for the Falcon XT
device. When Temperature is selected, the relative temperature alarm GP-O is closed,
while Audio Input Failure means lack of audio input at the input selected in the Input Setup
(Audio Control - Inputs - Input Setup), which can be set to either Analog or Digital. The lack
of audio closes
GPOut -2
on the rear port and triggers the alarm in the Alarm software. A
signal light appears on the front panel of the Falcon XT device at
GPOut -2.
If Clipping is
selected, an alarm is generated in the event of continuous Clipping, which also reaches the
Clipping Hardware.
In the event of an Audio Input Failure, a signal light
appears on the front panel of the Falcon XT at the
GPOut -2.
15 THE MPX GENERATOR
Let’s assume that the MPX signal is composed of three main
components
:
•
audio signal (L and R channels)
•
pilot tone (19 kHz)
•
RDS signal (57 kHz)
The stereo encoding process modulates (double-sideband suppressed-carrier) the LH-RH or stereo difference signal into
a 38kHz subcarrier. Its sidebands will extend by +/ - 15kHz. At the upper end this will amount to 53 kHz. A digital filter
ensures that all the content above 53 kHz is suppressed. This accuracy with which the spectrum is controlled
contributes to the sound level, since it ensures no excess energy is transmitted.
Note that the composite clipper does not degrade the RDS signal as it is applied before the 19kHz pilot is added to the
multiplex signal (if the pilot was present at the composite clipping stage, the third harmonic of the pilot generated by the
clipping process would fall on exactly 57kHz, thereby downgrading the RDS.)
Each component of the MPX signal is
generated digitally and, therefore, available at the highest quality.
| THE MPX GENERATOR
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Summary of Contents for Falcon VS
Page 1: ...Falcon XT User Manual FM Audio Processor Rev 2 2 ENG...
Page 25: ...BLOCK DIAGRAM OF FALCON XT 10 BLOCK DIAGRAM OF FALCON XT BLOCK DIAGRAM OF FALCON XT 25...
Page 96: ...TECHNICAL APPENDIX 20 6 4 Operative Example TECHNICAL APPENDIX 96...
Page 106: ...APPENDIX I FALCON XT MIB 23 APPENDIX I FALCON XT MIB APPENDIX I FALCON XT MIB 106...