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PSM-500/500L/500LT SCPC Satellite Modem
enable this feature simply supply the <Mod: BUC – LO Frequency> parameter with a value
other than "0". When the value set here is equal to the BUC's LO frequency then the modem can
automatically compute the RF frequency at the BUC output.
The PSM-500L modem will also determine if the LO is high or low side and sets the spectrum so
that it is always "Normal", i.e. not inverted. You do not have to change the IF spectrum setting
from "Normal" to achieve this.
Note: After entering a new BUC LO frequency the modem requires a new Transmit IF
frequency input to recalculate the proper output frequency setting.
To return to using the L-Band IF frequency setting, simply enter a value of "0" into the BUC LO
parameter. A common BUC LO frequency for the C-Band 5.925 to 6.425 GHz Range is 4900
MHz (low side LO), while a low side LO for the Ku Band 14.0 to 14.5 GHz range is 13150 MHz.
2.9.1.4 Using The L-Band & L Receive RF Frequency Feature
The L or LT models can cover the entire satellite's transmit range on it's receive input. This input
can be tuned to any frequency on 1 Hz increments in the 950 to 1900 MHz range. The coverage
can be "projected" to the actual satellite RF frequency being received at the LNB input. To enable
this feature simply supply the <Dem: LNB – LO Frequency> parameter with a value other than
"0". When the value set here is equal to the LNB's LO frequency then the modem can
automatically compute the RF frequency at the LNB input.
The L/LT modems will also determine if the LO is high or low side and sets the spectrum so that it
is always "Normal", i.e. not inverted. You do not have to change the IF spectrum setting from
"Normal" to achieve this.
Note: After entering a new LNB LO frequency the modem requires a new Receive IF
frequency input to recalculate the proper input frequency setting.
To return to using the L-Band IF frequency setting, simply enter a value of "0" into the LNB LO
parameter. A common LO frequency for the C-Band 3.7 to 4.2 GHz Range is 5150 MHz (high
side LO), while a common LO for the Ku Band 11.7 to 12.2 GHz range is 10750 MHz (low side
LO).
2.9.2 Carrier Acquisition Parameters
The PSM-500 Modem has two main modes and several programmable receive carrier acquisition
parameters available. These parameters control the initial acquisition of a carrier and
reacquisition of a carrier when it has been removed and reapplied.
There are two main acquisition methods used by the PSM-500. The normal mode for fastest
possible acquisition (especially at low data rates) is the "Fast" mode which utilizes an onboard
digital signal processor (DSP) to mathematically determine the location of the carrier and lock as
fast as possible. This mode initially goes for the largest carrier power within the acquisition range.
A new acquisition attempt will always repeat the same process and go to the same carrier. The
"fast" acquisition mode is optimized for the fastest possible acquisition speed, and is set as the
default acquisition mode for the modem.
A second mode called "Search" also uses the DSP but performs a piece-wise sweep of the
programmable acquisition range to locate the carrier and lock to it. If the modem cannot lock to
the first carrier it detects it will attempt to find another carrier in the next step of frequency. The
sweep always starts at the low end of the acquisition range and moves upward, wrapping around
to the low end when the top is reached. The Search mode is optimized for crowded spectrum
applications where nearby high power carriers may interfere with the standard "Fast" acquisition
mode. To our knowledge no one has ever had a problem using the standard Fast mode over
several years with many thousands of units, but the "Search" mode is still supplied just in case.
PSM-500/500L/500LT - Rev. 0.91
Installation
Page 2-17
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