User's Manual

The trace was in Figure 5-17 captured at the 12 dB tap on the upstream input to the W-CMTS.
It is centered on upstream frequency 6.4 MHz and built up with Max Hold for 30 seconds. Note
that the bursts from the various WCMs are arriving at nearly the same amplitude. [Disregard
signal below 4 MHz as noise, etc.].
-80
-70
-60
-50
-40
-30
-20
-10
0
10
2
3
4
5
6
7
8
9
10
11
Ref Level :
10.0 dBmV
dB / Div :
10.0 dB
M1
Spectrum Analyzer
30 SECS
Model: MS2711B Serial #: 00215050
Date: 05/23/2002 Time: 11:10:30
RBW: 1 MHz VBW: 30 kHz Detection: Average
CF: 6.4 MHz SPAN: 10.0 MHz Attenuation: 0 dB
dBmV
Frequency (1.4 - 11.4 MHz)
M1: -42.55 dBmV @ 11.4 MHz
Figure 5-17: Spectrum at Upstream input to W-CMTS.
See also Figure 5-19, which was taken at the same point at another installation.
There is an important subtlety here. The individual modem bursts are not spikes as this display
might suggest. Rather, each is a “standard” QPSK modulation envelope, 3.2 MHz wide,
centered at 6.4 MHz. They appear as spikes as the bursts are very short duration relative to the
sweep of the spectrum analyzer “window”. Thus only portions of the modulation envelope are
captured in the display.
5.7 Installation Labeling and Documentation
It is strongly recommended that the installer thoroughly document the system after turn-up and
a small number of pilot subscriber installations are complete and active – preferably at least one
in each sector. A copy of this documentation should be kept in a binder at the base station for
maintenance personnel access and hand updates as changes are made.
Examples of mandatory labels:
• Base station cabling: should be labeled at both ends as to its application: e.g. “Sector 3
U/S”, or “DC to Sector 1”. Many antenna installers utilize bands of colored tape to
identify cabling running from the equipment room to the antennas. If so installed, a ‘key’
to the coding should be posted: “red-red-yellow = Sector 1 D/S”
• 12 dB tap points: “Sector 3 D/S”
• Upconverters (CADCO): “511 MHz – Sectors 1,3,5”
• Sector number approximate compass direction: “Sector 1 – North, Sector 2 – NE, etc.”
June 2003 Page 5-20