User's Manual

DMR repeater 24/01/2011 Versione 1.1
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Menu item Description
Synchronism source Allows to choose the synchronism source
No sync No Synchronism source selected
Digital
Synchronism based on a proprietary pattern sent at the beginning of the
transmission and then on superaudio tones.
Internal
The synchronism source is a crystal oscillator placed inside the DSP module, which
has a stability better than 0.5 ppm in the thermal range of functioning. On demand,
higher stability oscillators can be used. The frequency tuning is digitally controlled
and the setting can be stored. An internal self calibration function allows to correct
the natural aging of the oscillator, by simply connecting the receiver to a calibrated
external source.
From multichannel
The synchronism is obtained from Audio LAN connection clock (patch cord on the
rear of the rack). This synchronism can be required for systems with more digitally
linked together radio stations.
Equipment synchronization time <2 s
Long period relative stability 0 ppm
Short period relative stability <0,001 ppm
From PPS GPS
The GPS receiver (inside the station) provides a pulse every second, which is used by
the DSP to clear its frequency and time reference. The time reference allows
automatic equalization of absolute delays of the links (useful in networks with IP
links or MUX SDH links with automatic reconfiguration of routes in case of backbone
failure). In the case of GPS failure the synchronism is automatically switched to
super-audio tone received from the master station (see following method).
Equipment synchronization time <120 s
Long period relative stability 0 ppm
Short period relative stability <0,01 ppm