User's Manual Part 2

Tech-X Flex User Guide - Firmware v06.50 Tech-X Flex
®
(NG2)
8-18
Intro
Overview
Wi-Fi
Ethernet
System
IP/Video
MoCA
RF
Specs
8.7.2 About out-of-band (OOB) channel support
The unit supports power measurements on OOB channels using the Single Channel Test and the
Channel Sweep Test. An OOB channel is a provider-specific channel typically used for the transfer of
data between a set-top box (STB) and provider equipment, such as the interaction with an on-screen
channel guide. An OOB channel normally uses a non-standard single frequency chosen specifically to
serve the desired purpose without interfering with normal channel frequencies.
To enable testing on OOB channels, you must:
Have the channel(s) configured in the main channel list (EIA, etc.). The main channel list is fixed on
the unit according to the installed firmware package. For more information, see EIA CATV tab on
page 8-7.
Have the channel(s) configured in the active channel guide, such that they may be specified for the
Single Channel Test and/or Channel Sweep Test setup. Like any channel, they must be specified
exactly as shown in the active channel guide. For more information, see Lineup tab on page 8-8 and
Download RF Channel Guide(s) on page 8-23.
Only power level measurements are performed on OOB channels. When an OOB channel is tested, no
other results will appear. Furthermore, the unit supports separate pass/fail thresholds for OOB channels,
up to a maximum of two separate channels. For more information, see About out-of-band (OOB) channel
support on page 8-18.
8.7.3 About QAM and the constellation graph
QAM (Quadrature Amplitude Modulation) is one of many methods for transporting digital data over
analog waveforms such as RF sine waves. With QAM, the fundamental technique of representing digital
bits is through amplitude modulation of the analog waves, where a prescribed set of amplitudes are
assigned to different binary digits.
As an example of amplitude modulation, consider an amplitude scheme that is segmented into four
different levels. This type of scheme can present one of four digits (that is, two bits) with each wave cycle,
with the following hypothetical wave modulated with a binary “10”:
Figure 8-11 Hypothetical RF waveform representing a binary 10 (decimal 3)
00
01
10
11
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