STM SatLink VSAT - Configuring P1 dB (End of Linear Range)

SatLink VSAT User Guide
Publication no. 101557
Rev 14.1.1-2
Copyright 2006-2012 – STM Group, Inc.
Page 163 (182)
I.2 Configuring P1dB (End of Linear Range)
This section describes how to configure the P1dB (end of linear range) for 3
rd
party BUCs (without
support for DiSEqC and an integrated power detector) to avoid entering in saturation when up link power
control is enabled.
A BUC maintains a constant linear gain for low-level input signals. However, at higher
input levels, the amplifier enters in saturation and its gain decreases (becoming non-linear).
The P1dB (1 dB compression point) indicates the power level that causes the linear gain to
drop by 1 dB, as indicated in the following formula:
P1dB
[Output]
= P1dB
[Input]
+ Linear Gain - 1 dB
Check with your Hub operator for the procedure to be used to determine the P1dB compression point of
the 3
rd
party BUC (the procedure could be similar to the one described above for the calibration of the
output power). The P1dB will be associated to a certain TX IDU output power, then to avoid the BUC
entering in saturation, that associated TX IDU output level must be configured as the ―IDU Max Output
Power‖.
Configure the P1dB using the CLI command:
dvb tx outpow –max <pow>
where “pow” is the TX IDU Output Power level in dBm associated to the P1dB.
The IDU will limit its Max Ouput Power to the “pow” value configured above.
Verify the setting for ―IDU Max Output Power‖ is “pow”, by issuing the following CLI command:
dvb tx show
Save the setting by issuing the following CLI command:
save config
Example:
Let‘s consider the P1dB is associated to a TX IDU Power Level of -8 dBm, then type the CLI command:
dvb tx outpow –max –8
Verify the setting for ―IDU Max Output Power‖ is -8 dBm by issuing the following CLI command:
dvb tx show
Save the setting by issuing the following CLI command:
save config
More Examples:
dvb tx outpow -5 sets IDU Output Power to -5 dBm
dvb tx outpow -12 sets IDU Output Power to -12 dBm
dvb tx outpow -max -1 sets IDU Max Output Power to -1 dBm
dvb tx outpow -max -3 sets IDU Max Output Power to -3 dBm