Downstream (Rx) Receive Power Level:
This is the amount of signal received by the modem from the transmitter in the cable company head-end.
For all modems:
-10 dBmV to +10 dBmV "Recommended".
-11 dBmV to -14 dBmv / +11 dBmV to +14 dBmV "Acceptable".
-15 dBmV & +15 dBmV "Maximum".
Upstream (Tx) Transmit Power (a.k.a. Return Signal) level:
This is the amount of signal transmitted by the modem to reach the receiver in the cable company head-end.
+8 dBmV to +58 dBmV maximum for QPSK. (DOCSIS 1.0, 1.1)
+8 dBmV to +55 dBmV maximum for 8 QAM and 16 QAM. (DOCSIS 1.0, 1.1)
+8 dBmV to +54 dBmV maximum for 32 QAM and 64 QAM. (A-TDMA DOCSIS 2.0)
+8 dBmV to +53 dBmV maximum for S-CDMA DOCSIS 2.0 (All Modulations)
*Recommended upstream signal levels are +35 dBmV to +52 dBmV.
1. Signal levels not within specs can cause slow speeds, connection problems, and connection loss due to packet errors, packet loss, and/or constant packet retransmission.
2. It's recommended to have the modem's signal levels at least 3dB away from the maximum/minimum levels listed above due to normal temperature related signal variation. If the modem's signal levels are at the maximum or minimum limits, they may be out of spec. if the temperature changes significantly. Signal levels that vary more then 3 dB in a 24-hour period usually indicate a problem that should be looked into.
3. Excess splits, bad connectors, and/or poor quality cabling will certainly effect cable signal levels and will cause problems.
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by drake  edited by lilhurricane
last modified: 2009-10-25 14:01:06 |
