Xicom XTU-400K, Operation And Installation Manual

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MNC-0000-015 7 of 8 Revision C
Operation Addendum, Block Upconverter
•
DBS Band — (16.35 GHZ/Reference Frequency) X
Reference Offset = Output Offset.
Reference Offset is in MHz.
2. To turn ON the HPA (High Power Amplifier) refer to the chapter
titled Operation . The internal attenuator must be set to minimum
value and gradually increased to achieve rated power.
The input power to the BUC should not exceed -17 dBm to minimize
system spurious output. The maximum safe IF input power level is 10
dBm to avoid damage to the internal converter circuits.
3. Refer to the appendix titled Protocol Addendum, Block
Upconvert for a description of the protocol and system interface
to the BUC. The BUC has an internal lock detect which senses
the presence of the reference frequency and proper functioning
of the internal PPL (Phase Lock Loop). The absence of either
the reference frequency or a loss of lock in the PLL results in a
system fault and the system internal fault detection circuit
disables the HPA high voltage circuit.
Note
The power levels and frequencies discussed in the
paragraphs above are representative of typical BUC
performance. The specific power levels and
frequencies that the BUC in the HPA that this manual
apply to are identified in the appendix titled
Product
Specification .
Reference Oscillator Drift Compensation
Over extended time periods, the 10MHz reference oscillator
changes frequency due to temperature / aging and results in a shift
in the output frequency that can /- 10kHz. Depending on
the system budget, the converter must be re-adjusted to stay within
its allocated transponder band and within the receiver acquisition
range. Check the system specification to determine the allowable
frequency drift range and periodically monitor the system output
frequency through the RF sample port.
In the event that the frequency drifts outside the acceptable range,
the unit must be either re-aligned by a Xicom certified maintenance
center or alternatively the modem L Band output must be adjusted
to correct the output frequency. Adjusting the L Band modem
frequency is the simplest method and is recommended. The drift
compensation scheme is summarized in Figure 4.