Specifications

Seasonal/diurnal signal
level variation
8 dB 8 dB
Signal level slope (50 to
750 MHz)
16 dB 16 dB
Maximum analog video
carrier level at the CM
input, inclusive of above
signal level variation.
+17 dBmV +17 dBmV
Minimum analog video
carrier level at the CM
input, inclusive of above
signal level variation.
−5 dBmV −5 dBmV
Digital Signal Levels
Input to cable modem
(Level range, one
channel)
−15 to +15 dBmV −15 to +15 dBmV
Signal as relative to
adjacent video signal
−6 to −10 dBc −6 to −10 dBc
Notes for Tables
*1 −DOCSIS specifications are baseline settings for a DOCSIS−compliant, two−way data−over−cable
system.
*2 − Minimum settings are slightly different than the DOCSIS settings to account for cable system variations
over time and temperature. Using these settings should increase the reliability of DOCSIS−compliant,
two−way data−over−cable systems.
*3 − QPSK = Quadrature Phase−Shift Keying: a method of modulating digital signals onto a radio−frequency
carrier signal using four phase states to code two digital bits.
*4 − These settings are measured relative to the digital carrier. Add 6 or 10 dB, as determined by your
company's policy and derived from the initial cable network setup, relative to the analog video signal.
*5 − QAM = Quadrature Amplitude Modulation: a method of modulating digital signals onto a
radio−frequency carrier signal involving both amplitude and phase coding.
*6 − dBc = decibels relative to carrier.
Note: For a full set of the specifications for the European Standard, please read RF Specifications.
Checking the Downstream
When checking the downstream interface begin by ensuring that the configuration is correct. In most cases
when configuring the downstream cable interface on the CMTS the default values are sufficient. You do not
need to specify individual parameters unless you want to deviate from system defaults. Use the output below
to match the downstream configuration parameters with the matching values seen in the show commands on
the CMTS and the cable modem.
Cisco − Determining RF or Configuration Issues On the CMTS