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Chapter 9
Measure Mode – Service Tab
DOCSIS
212
DSAM Help User Guide
Rev. 001
Test Complete
Results
Directly below the overall pass/fail result is an indication that the test
was completed successfully (Test Complete), or an indication of what
error occurred.
High Sensitivity Mode
This icon is displayed if QAM Sensitivity is set to high on the Other
Settings configuration screen. (See
“Other Settings Parameters” on
.)
MER Headroom
The DSAM default limits are set at the recommended minimum MER
values for a TV/Modem. The default limit for 64 QAM carriers is 28 dB.
The default limit for 256 QAM carriers is 32 dB. You can set other limit
sets at the Limit Sets screen (
). If limits is set to
Off, the MER Headroom reading is not applicable.
Downstream/
Upstream Pass/Fail
Results
A column to the far left of the downstream and upstream sections indi-
cates the pass/fail status for each item tested. When a measurement
falls outside the selected limit set range, an up or down arrow head is
displayed to the right of the measurement indicating that the value is
too high or too low. Numeric values that are out-of-range appear in
bold.
LEVEL Headroom
LEVEL Headroom is the difference between the maximum output
possible (58 dBmV for QPSK or 55 dBmV for 16 QAM) and the LEVEL
transmitted. Upon successful ranging with the network CMTS, DSAM
displays the resultant upstream transmit LEVEL required out of the
DSAM. This LEVEL Headroom is tested against the “Min CM Head-
room” limit value if limits is set to On.
EXAMPLE 1
A MER reading of 36 dB is obtained from a 64 QAM DOCSIS car-
rier when your limits are set to “Cable Modem” and you are using
the DSAM factory default limits. The MER Headroom calculation
results display a reading of 8 dB (36 dB - 28 dB = 8 dB).
EXAMPLE 2
An MER reading of 36 dB is obtained from a 256 QAM DOCSIS
carrier when your limits are set to “Cable Modem” and you are using
the DSAM factory default limits. The MER Headroom calculation
results display a reading of 4 dB (36 dB - 32 dB = 4 dB).
NOTE
No pass/fail information is available when limit check is disabled.
21128026 R001 DSAM Help User Guide.book Page 212 Thursday, February 5, 2009 2:02 PM