Figure A-2. Minimum Symbol Rate Versus Satellite Uncertainty For Ku-Band And C-Band - Comtech EF Data DST Operator's Manual

Digital Satellite Terminal System
Operation
The Ku-Band error budget with the 3 ppm LNB was presented earlier, and the budget for
an externally referenced LNB at 0.02 ppm follows:
± 309 Hz
± 215 Hz
± 58 Hz
± 10,000 Hz
± 10,582 Hz
21,164 Hz
8,140 sps
The highest stability and least amount of frequency uncertainty is provided when an
externally referenced LNB (and BUC) is connected to a modem with a ±0.02 ppm
reference.
50
45
40
35
30
25
20
15
10

Figure A-2. Minimum Symbol Rate versus Satellite Uncertainty for Ku-Band and C-Band

BUC with LO = 15,450 MHz, ±0.02 ppm
LNB with LO = 10,750 MHz, ±0.02 ppm
Modulator + Demodulator at 1,450 MHz, ±0.02 ppm
Satellite Uncertainty
± Uncertainty
Convert ± to total End to End
x 2
End to End Uncertainty fv
÷ 2.6 2 * k, where k = 1.3
SR ≥ fv /(2 * 1.3), minimum symbol rate for 1.3 carrier spacing
Minimum Symbol Rate (vs) Satellite Uncertainty
BUC = +/- 0.02 ppm, Modem +/- 0.02 ppm
Ku-Band
LNB = +/- 3 ppm
C-Band
LNB = +/- 3 ppm
Ku-Band or C-Band
LNB = +/- 0.02 ppm
5
0
0 5 10 15
Satellite Uncertainty (+/- kHz)
A–4
MN/DST.IOM
20 25
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