Microwave Radio Communications SCM4000, Техническое справочное руководство, Страница: 205 / 274

Troubleshooting 4-15 SCM4000 Operator’s Guide/Tech Ref Manual
No Data/Corrupted
Data Incorrect data rates - The modem is very
sensitive to the rates at which the
channels are set. Mismatched data rates,
i.e., data rates that are not the same on
the Modulator and Demodulator, can
cause corrupted data. An incorrect data
rate in one channel can cause errors in
many more channels. This is due to the
fact that, just like RF, an incorrectly
configured channel can “walk” on other
channels. • Verify that the Modulator and
Demodulator have matching data rates
for all channels, including channels not in
use.
• Contact technical staff.
If problem persists,
possible hardware failure.
Contact MRC Technical
Support .
Table 4-8: General System Problems (Continued)
Problem Possible Cause Suggested Operator Action
Suggested Technical
Staff Action
Note that PRBS will not display valid data if the
Demodulator is unlocked.
4. Turn on PRBS on the Modulator. See ”Monitor/
Change PRBS State” on page 3-74 .
5. Turn on PRBS on the Demodulator. See ”Monitor/
Change PRBS State” on page 3-112 .
6. Reset PRBS on the Demodulator. See ”Reset PRBS”
on page 3-116 .
7. After approximately 5 minutes, Bit Error Rate (BER)
errors should be 0.000e+00 to 1.000e-07.
See
”Monitor PRBS Bit Error Rate” on page 3-114 .
4.5 Link Setup Guide
This paragraph provides the steps required to use Pseudo
Random Bit Sequence (PRBS) to verify a good transmission link.
1. Set up an RF link.
2. Set Symbol Rate (SR) and modulation modes to match
on the Modulator and Demodulator.
3. Verify that you have carrier lock. If not, adjust RF and
SR until you have carrier lock.
Refer to the “Symbol Rate Calculations” Appendix on
page C-1 to determine bit rate vs. symbol rate vs.
QPSK, 16QAM, 32QAM, and 64QAM modulation
rates.