Measuring System Performance: Modem Carrier-to-Noise Measurements
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Enter the BANDWIDTH submenu; return to C/N main menu.
Enable or disable 13 dB amplifier
Enable or disable 50 MHz low-pass filter (icon shows
disabled)
Fig. 6-6 Carrier-to-Noise Measurement
NOTE: The US FCC specification for C/N measurements
is a bandwidth of 4.000 MHz. CATV organizations outside
of the United States may have different requirements.
Measuring carrier-to-noise (C/N) on return-path cable modem signals has
never been an easy assignment. One difficulty has been the detailed set-up
of the test equipment required to make the modem C/N measurement. The
test equipment is usually a spectrum analyzer used in a zero-span operating
mode, which requires you to be well acquainted with set-up parameters such
MODEM CARRIER-TO-NOISE MEASUREMENTS
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