Motorola DIMETRA MTS 2, Installation, Configuration And Basic Service Manual

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MTS 2 and MTS 4 Installation, Con
fi
guration and Basic Service Manual Cavity Combiner
Cavity Combiner
There are two types of Cavity Combiners available:
•
Auto Tune Cavity Combiners (ATCC)
•
Manual Tune Cavity Combiners (MTCC)
MTCCs are functionally the same as ATCCs except that they are tuned manually instead of electronically.
MTS 2 does not support Cavity Combiners.
Minimum channel spacing of the TX channels is 150 kHz while the recommended channel spacing is 250 kHz.
Figure 7-24 Auto Tune Cavity Combiner
Cavity Combiner - Theory of Operation
A minimum of 2 watts is needed at a cavity input. The ATCC will automatically tune in 40
seconds maximum. For more detail, refer to the ATCC speci
fi
cation.
Once an RF signal greater than 2 watts is detected, the ATCC tunes the cavity and continuously
keeps it tuned over humidity, temperature and changing transmit frequency, so long as it
does not sense one of the following alarm conditions:
•
Channel Spacing alarm
•
VSWR alarm
•
Failure to Tune alarm
Being tuned means that a cavity is within the insertion loss speci
fi
cation at the frequency of the applied
PI/4DQPSK or QAM4,16,64 signal that is within the average input power range speci
fi
ed above. Being tuned
also means that the cavity peak response is no greater than 25 kHz away from the TX carrier centre frequency.
6802800U74-N September 2009
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