Optional Procedure To Determine Pn Max Power - iDirect evolution x1 Installation Manual

Optional Procedure to Determine PN Max Power

8. Click the Stop button in iSite or Web iSite to turn off the CW carrier.
Note: Do not re-start or remove power from the Satellite Router.
The 1 dB compression point has now been established. Either perform the optional procedure
in next section or disconnect the access control center from the call and proceed to
"Acquiring the Network" on
15.3 Optional Procedure to Determine PN Max Power
The optional procedure in this section determines the maximum transmit power of the
Satellite Router using a modulated pseudo-noise code (PN) test carrier. The result of this
procedure is entered by the Network Operator as a remote custom key. When the custom key
is present, this setting is used instead of the configured iBuilder Maximum Power to limit the
Satellite Router transmit power during normal operation. There are a number of benefits of
executing this procedure and configuring the custom key.
Newer low-cost BUCs use quasi-linear final stage amplifiers (Class AB) to improve DC power
consumption and to keep the BUC form factor to a minimum. These BUCs compress a CW tone
much earlier than a modulated carrier. There can be as much as 3 dB difference in maximum
EIRP when the maximum power is determined using a modulated PN carrier versus a CW
carrier. This discrepancy is mainly due to the crest factor difference in the waveforms that
results in shifting the bias point of the amplifier. Linear BUCs do not exhibit this
characteristic, making the EIRP difference for those BUCs less significant.
Adaptive TDMA reduces the need to provision VSAT terminals with large rain fade margins.
This improves throughput in clear sky conditions. Since a terminal so provisioned operates
very near its maximum output power under most conditions, proper determination of
maximum power is extremely important in an Adaptive TDMA system.
The maximum power must be configured such that the levels do not exceed the target
Adjacent Channel Interference (ACI). The procedure defines maximum power to be the power
which meets the maximum Adjacent Channel Power Ratio (ACPR) limit permitted by the
spacecraft operator for the modulated carrier. The acceptable ACPR varies depending upon
the particular spectral mask definition, which in turn varies by signal type, transponder, and
spacecraft operator. This procedure generates a BPSK PN sequence. The default Symbol Rate
of 128 ksps should be used for this procedure. This carrier configuration produces a worst-
case ACPR compared to all other MODCODs and symbol rates supported in iDirect networks.
Note: This procedure assumes the acceptable side lobe level is -20 dBc.
Note: This procedure assumes that the maximum power configured on the Satellite
Router is set to the highest possible value. The maximum values are: 0 dBm for
X1 or e150 Satellite Routers; +5 dBm for all other Satellite Routers.
To Determine Maximum Power:
1. After performing the P1dB compression test, ask the access controller for permission to
radiate a modulated carrier. The test carrier requires 154 kHz of satellite bandwidth.
2. Advise the access controller to configure the spectrum analyzer as follows:
• Resolution BW: < 8 kHz
• Span: 800 kHz
• Vertical scale: 2 dB/div
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page 91.
iDirect Satellite Router Installation and Commissioning Guide
iDX Release 3.3