Sencore SMD 989 - Page 77

SMD 989– User Manual
Page 77 (105)
BAY 1: MODULATOR MODULATION ↕
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>ALPHA FILTER ROLLOFF: 0.35
CLEAN CARRIER ONLY: DISABLED
RATE ADAPTATION: ENABLED
PL SCRAMBLING CODE: 000000
PRBS: DISABLED
Note: When the SMD 920 L-Band option is installed, the default spectral inversion is inverted as
the upconverter is set to invert. Setting the output to Inverted will give a normal output from the
upconverter. This is shown in the RF Output status for Spectral Inversion.
Alpha Filter Rolloff
- 0.35
- 0.25
- 0.20
- 0.15
- 0.10
- 0.05
Description: The filter rolloff is known as the Alpha coefficient (α). The smaller the α, the less
bandwidth will be required on the satellite. Rolloff in DVB-S limited to 0.35, 0.25 and 0.20.
Clean Carrier Only (Disabled/Enabled)
Description: When set to Enabled the modulator outputs only a cw carrier for testing purposes.
Rate Adaptation (Disabled/Enabled) Only available in DVB-S2 or DVB-S2X single mode)
Description: When enabled a rate adaption is applied. When disabled the rate adaptatiois not
active. Rate adaptation adds or removes null packets and re-stamps PCRs in order to match TS
bitrate to the modulation payload rate.
PL Scrambling Code (6 digit value entry)
Description: This is used to specify a randomized scrambling sequence applied to each
PL frame and initiated at the end of each PL header. Scrambling randomizes band energy
dispersion and allows for a “signature” when may provide association to a satellite operator or
satellite. The complex code relates to an “n” value defined by an entry of 0 to 262 141.
PRBS (Enabled/Disabled)
Description: When Enabled the PRBS replaces the normal input modulation feeding the
modulator with a PN23 normal or inverted BERT test signal. Select Disabled for normal output
applications.
IMPORTANT: For normal or non-testing applications in which the input is to be used to
modulate the satellite IF or L-Band carrier output, the PRBS test signal must be set to
DISABLED.