**Tests of ATSC 8-VSB Reception Performance\
of Consumer Digital Television Receivers Available in 2005**

**November 2, 2005**

**Technical Research Branch**

**Laboratory Division**

**Office of Engineering and Technology**

**Federal Communications Commission**

**OET Report Prepared by:**

**FCC/OET TR 05-1017 Stephen R. Martin**

**FOREWORD**

The author gratefully acknowledges the advice and technical support
offered by the following individuals and organizations. Gary Sgrignoli
and Dennis Wallace of MSW provided technical guidance at the inception
of the project, and Gary Sgrignoli also provided guidance later and
reviewed an early draft of this report. Mark Hryszko, Mike Gittings,
Raul Casas of ATI Research, Inc. identified degraded performance of the
FCC's RF capture player (which was subsequently repaired and calibrated
before conducting the tests reported herein) and provided technical
advice; Mark Hryszko and Kevin Murr assisted in comparative testing at
ATI's laboratory using ATI's equipment as a double-check of the FCC
equipment and measurement procedures for the FCC Laboratory tests
reported herein. Wayne Bretl of Zenith Electronics Corp. and Rich Citta
of Micronas Semiconductors, Inc. provided technical advice regarding
testing with RF captures. Victor Tawil of the Association for Maximum
Service Television (MSTV) and Sean Wallace of Wavetech Services, LLC
provided RF captures and technical advice.

**TABLE OF CONTENTS**

[EXECUTIVE SUMMARY iv](#executive-summary)

[Samples iv](#samples)

[Test Results iv](#test-results)

[CHAPTER 1 INTRODUCTION 1-1](#introduction)

[Background 1-1](#background)

[Objectives 1-1](#objectives)

[Ability to Receive Signals 1-2](#ability-to-receive-signals)

[Standard for Determining Whether a Household is Unserved
1-4](#standard-for-determining-whether-a-household-is-unserved)

[Overview 1-4](#overview)

[CHAPTER 2 SCOPE AND APPROACH 2-1](#scope-and-approach)

[Scope of Testing 2-1](#scope-of-testing)

[Test Samples 2-1](#test-samples)

[Test Philosophy and Approach 2-3](#test-philosophy-and-approach)

[CHAPTER 3 WHITE-NOISE THRESHOLD MEASUREMENTS (REQUIRED CARRIER-TO-NOISE
RATIO)
3-1](#white-noise-threshold-measurements-required-carrier-to-noise-ratio)

[Measurement Method 3-1](#measurement-method)

[Format of The Bar Graph Data 3-2](#format-of-the-bar-graph-data)

[Results 3-2](#results)

[CHAPTER 4 MINIMUM INPUT SIGNAL MEASUREMENTS
4-1](#minimum-input-signal-measurements)

[Measurement Method 4-1](#measurement-method-1)

[Results 4-2](#results-1)

[CHAPTER 5 INFERRED NOISE FIGURE 5-1](#inferred-noise-figure)

[Results 5-2](#results-2)

[CHAPTER 6 PERFORMANCE AGAINST MULTIPATH USING FIELD CAPTURES
6-1](#performance-against-multipath-using-field-captures)

[Measurement Method 6-1](#measurement-method-2)

[Results 6-2](#results-3)

[CHAPTER 7 INFERRED PERFORMANCE AGAINST REPRESENTATIVE MULTIPATH
CONDITIONS
7-1](#inferred-performance-against-representative-multipath-conditions)

[Multipath Capability Based on Year-2000 Field Tests
7-1](#multipath-capability-based-on-year-2000-field-tests)

[Impact of Representative Multipath on Required CNR
7-2](#impact-of-representative-multipath-on-required-cnr)

[CHAPTER 8 SUMMARY AND CONCLUSIONS 8-1](#summary-and-conclusions)

[Variation in Reception Performance
8-2](#variation-in-reception-performance)

[Price-Dependence of Reception Performance
8-3](#price-dependence-of-reception-performance)

[Reception Performance Relative to OET-69
8-3](#reception-performance-relative-to-oet-69)

[APPENDIX A TEST CONFIGURATIONS, ISSUES, AND PROCEDURES
A-1](#summary-and-conclusions)

[Test Configurations A-1](#test-configurations-1)

[Calibration and Signal Quality Tests on Test Setups
A-2](#calibration-and-signal-quality-tests-on-test-setups)

[Test Issues A-4](#test-issues)

[Procedures A-6](#procedures)

[Equipment A-11](#equipment)

[APPENDIX B SUMMARY OF RF FIELD CAPTURES B-1](#summary-and-conclusions)

**ILLUSTRATIONS**

[Figure 3‑1. Measured White Noise Threshold of Receivers
3-5](#__RefHeading___Toc118693135)

[Figure 4‑1. Measured Minimum Signal Level at TOV on Three Channels
4-5](#__RefHeading___Toc118693136)

[Figure 4‑2. Measured Minimum Signal Level at TOV on Channel 3 (Low VHF)
4-5](#__RefHeading___Toc118693137)

[Figure 4‑3. Measured Minimum Signal Level at TOV on Channel 10 (High
VHF) 4-6](#__RefHeading___Toc118693138)

[Figure 4‑4. Measured Minimum Signal Level at TOV on Channel 30 (UHF)
4-6](#__RefHeading___Toc118693139)

[Figure 4‑5. Measured Minimum Signal Level at TOV Versus Channel for
Receiver G2 4-7](#__RefHeading___Toc118693140)

[Figure 4‑6. Measured Minimum Signal Level at TOV Versus Frequency for
Receiver G2 4-7](#__RefHeading___Toc118693141)

[Figure 5‑1. Relationship between Minimum Signal at TOV and Required CNR
5-5](#__RefHeading___Toc118693142)

[Figure 5‑2. Noise Figure on Three Channels
5-5](#__RefHeading___Toc118693143)

[Figure 5‑3. Noise Figure on Channel 3 (Low VHF)
5-6](#__RefHeading___Toc118693144)

[Figure 5‑4. Noise Figure on Channel 10 (High VHF)
5-6](#__RefHeading___Toc118693145)

[Figure 5‑5. Noise Figure on Channel 30 (UHF)
5-7](#__RefHeading___Toc118693146)

[Figure 5‑6. Required CNR Versus Noise Figure
5-7](#__RefHeading___Toc118693147)

[Figure 6‑1. Performance Against 47 RF Captures
6-6](#__RefHeading___Toc118693148)

[Figure 6‑2. White Noise Threshold Versus Multipath Performance
6-6](#__RefHeading___Toc118693149)

[Figure A‑1. Block Diagram of Test Configuration for Required CNR and RF
Capture Tests A-12](#__RefHeading___Toc118693155)

[Figure A‑2. Block Diagram of Test Configuration for Minimum Signal at
TOV A-12](#__RefHeading___Toc118693156)

[Figure A‑3. Frequency Response of Each Port
A-13](#__RefHeading___Toc118693157)

[Figure A‑4. Effect of Load Impedance Mismatch
A-13](#__RefHeading___Toc118693158)

[Figure A‑5. Calibration Connection for Test Setup for Required CNR and
RF Capture Tests A-14](#__RefHeading___Toc118693159)

[Figure A‑6. Spectra of Injected Signal and Noise at 15-dB CNR
A-14](#__RefHeading___Toc118693160)

**TABLES**

[Table 1‑1. Planning Factors for DTV Reception Prediction
1-4](#__RefHeading___Toc118693178)

[Table 2‑1. DTV Receiver Samples 2-2](#__RefHeading___Toc118693179)

[Table 3‑1. Statistics of White Noise Threshold
3-3](#__RefHeading___Toc118693180)

[Table 3‑2. Product-Type/Price Variations of White Noise Threshold
3-3](#__RefHeading___Toc118693181)

[Table 3‑3. Correlation Coefficient of White Noise Threshold with Price
3-4](#__RefHeading___Toc118693182)

[Table 4‑1. Statistics of Minimum Signal Level at TOV
4-2](#__RefHeading___Toc118693183)

[Table 4‑2. Product-Type/Price Variations of Minimum Signal at TOV
4-4](#__RefHeading___Toc118693184)

[Table 4‑3. Correlation Coefficient of Minimum Signal at TOV with Price
4-4](#__RefHeading___Toc118693185)

[Table 5‑1. Statistics of Receiver Noise Figure
5-2](#__RefHeading___Toc118693186)

[Table 5‑2. Product-Type/Price Variations of Receiver Noise Figure
5-3](#__RefHeading___Toc118693187)

[Table 5‑3. Correlation Coefficient of Receiver Noise Figure with Price
5-4](#__RefHeading___Toc118693188)

[Table 6‑1. Number of Captures Successfully Played By Each Performance
Tier 6-3](#__RefHeading___Toc118693189)

[Table 8‑1. Net Performance for Unimpaired Signal Relative to OET-69
Model 8-4](#__RefHeading___Toc118693190)

[Table 8‑2. Planning Factor Measurements with Unimpaired Signal
8-4](#__RefHeading___Toc118693191)

[Table A‑1. Equipment List A-11](#__RefHeading___Toc118693192)

[Table B‑1. RF Field Captures B-2](#__RefHeading___Toc118693193)

# EXECUTIVE SUMMARY

This report presents the results of laboratory tests of over-the-air
digital (ATSC/8-VSB[^1]) reception performance of 28 consumer digital
television (DTV) receivers. The tests were performed to provide an
empirical basis for answering questions about DTV reception capability
that derive from study requirements imposed by Congress as part of the
*"Satellite Home Viewer Extension and Reauthorization Act of 2004"*
(SHVERA). The Act requires that the FCC conduct a six-element study. The
element relevant to this report is as follows:

> *"consider whether ... there is a wide variation in the ability of
> reasonably-priced consumer digital television sets to receive
> over-the-air signals, such that at a given signal strength some may be
> able to display high-quality pictures while others cannot, whether
> such variation is related to the price of the television set, and
> whether such variation should be factored into setting a standard for
> determining whether a household is unserved by an adequate digital
> signal."*

## Samples

Two categories of DTV receivers were acquired for this project: digital
set-top boxes (STBs) and DTVs with integrated over-the-air ATSC tuners.
All receivers are standard, off-the-shelf consumer products currently on
the market. STBs were included in the study because connection of an STB
to an existing television represents the lowest-cost alternative for DTV
reception. The measurement results in this document are reported by
category (STB or integrated DTVs) and, within the DTV category, by price
range (\$370 - \$1000, \$1001 - \$2000, and \$2001 - \$4200). Brands and
model numbers are not reported.

## Test Results

The tests performed for this report were laboratory-based measurements
emulating two types of over-the-air reception conditions for DTV
receivers:

> \(1\) Unimpaired signal (i.e., no multipath) \[Chapters 3 -- 5\], and
>
> \(2\) Signal impaired by multipath (ghosts) \[Chapter 6\].

The unimpaired signal measurements can be used to quantitatively predict
receiver performance under benign reception conditions---i.e., with
little multipath or interference. The multipath tests, which focus
primarily on particularly difficult multipath conditions, provide a
basis for comparing the ability of different DTV receivers to handle
difficult multipath conditions. A link between these laboratory-based
measurements and earlier FCC field-test data provides a basis for
anchoring the multipath results to representative, real-world reception
conditions \[Chapter 7\].

### Benign Multipath Conditions

Overall performance under benign reception conditions is indicated by
minimum signal level at the threshold of visibility of errors (TOV) for
each receiver. The median measured values of this parameter across all
of the tested consumer DTV receivers were -82.2 dBm, -83.2 dBm, and
-83.9 dBm, respectively, in the low-VHF, high-VHF, and UHF bands. These
values comply, within measurement accuracy, with the ‑83 dBm minimum
performance standard recommended by the ATSC. The corresponding medians
for just the low-cost category of DTVs (-83.3 dBm, -83.4 dBm, and
-84.1 dBm, respectively) were very slightly better than the medians
across all of the receiver categories.

OET Bulletin No. 69, *"Longley-Rice Methodology for Evaluating TV
Coverage and Interference"*, presents a methodology for predicting
whether a household is served by a given broadcast signal. The DTV
receiver model in that bulletin predicts minimum signal levels at TOV of
-81.0 dBm and -84.0 dBm for VHF and UHF, respectively. While the test
results presented in this report---together with data based on earlier
FCC field tests---could be used to fine tune those parameters, the net
effect of such changes would be small; consequently, no compelling
reason is seen for such fine tuning.

Variation in minimum signal at TOV among the receivers was found to be
moderately high in the low-VHF band, but small in the high-VHF and UHF
bands.

In the low VHF band (as represented by TV channel 3 in these tests), the
moderately high variability in performance among the samples is
indicated by the 3.7‑dB standard deviation among the receivers and the
fact that two same-brand receivers exhibited performance significantly
worse than the median---by 11 and 12 dB. (It is noted that, absent those
two receivers, the standard deviation would have been a more modest
2.3 dB.)

Though the performance variation among the receivers in the low VHF band
was moderately high, no statistically significant
[price-dependence]{.underline} of that variation was found. In fact, the
median performance of the low-cost TVs was slightly better than that of
either the mid-priced or high-priced TVs. The median performance of the
tested set-top boxes was poorer than that of the integrated DTVs by
2.3 dB, though it must be noted that these were older designs (2004 and
earlier models that were still on the market at the time of this report)
than the integrated DTVs.

In the high-VHF and the UHF bands (represented in the tests by channels
10 and 30, respectively), the variation in reception performance among
the tested receivers was small---as indicated by the 1.6‑dB standard
deviation in the high-VHF band and 0.9 dB in the UHF band. The variation
of performance with price was judged to be both small and not
statistically significant. The median performance of the high-cost TVs
differed from that of the low-cost TVs by less that 0.2 dB. Set top
boxes exhibited median performance 0.6 dB and 0.7 dB worse than the
median of all TVs in the low-VHF and UHF bands, respectively.

Most of the variation in reception performance among the tested
receivers was due to differences in *effective* noise figure rather than
in the carrier-to-noise ratio (CNR) required for successful
demodulation. The noise figure variations were larger than the
required-CNR variations by factors ranging from 4, in the UHF band, to
16, in the low-VHF band.

### Difficult Multipath Conditions

The tested receivers fall into two distinct tiers of multipath-handling
capability---the upper tier representing a significant performance
improvement associated with at least two companies' newest generation of
demodulator chips. While the difference in ability to handle difficult
multipath conditions between the two tiers is large, linkage of the
current results with earlier field test results (Chapter 7) suggests
that the observed performance differences are of no consequence in the
vast majority of reception locations, if an outdoor, mast-mounted
antenna is used. When an indoor antenna is used, the linkage suggests
that the observed performance differences would be significant in many,
but probably not most, locations.

Given that both tiers of performance appeared in all three price ranges
of DTVs, there appears to be no price dependence of multipath
performance; however, there was a complete absence of upper-tier
performers among the tested set-top boxes. This absence is attributed to
the older designs of the set-top box products---all of which were
introduced in the year 2004 or earlier. Among the tested DTV receivers,
none that were introduced before March 2005 were found to exhibit
upper-tier performance, whereas 48 percent of those introduced in or
after that month performed at the upper tier level.

#  INTRODUCTION

## Background

This report presents the results of laboratory tests of terrestrial
over-the-air digital (ATSC/8-VSB[^2]) reception performance of 28
consumer digital television (DTV) receivers. Though the tests involve
[terrestrial]{.underline} reception performance, the tests were
performed to provide an empirical basis for answering questions about
DTV reception capability that derive from study requirements imposed by
Congress as part of the *"Satellite Home Viewer Extension and
Reauthorization Act of 2004"* (SHVERA).

SHVERA, passed by Congress in December 2004, extends and amends the
*"Satellite Home Viewer Act of 1994"*. The Act allows satellite
communications providers to provide broadcast programming to satellite
subscribers that are unserved by local---over-the-air---broadcast
stations.

Section 204 of SHVERA requires that the Commission conduct an inquiry
regarding "whether, for purposes of identifying if a household is
unserved by an adequate digital signal under section 119(d)(10) of title
17, United States Code, the digital signal strength standard in section
73.622(e)(1) of title 47, Code of Federal Regulations, or the testing
procedures in section 73.686(d) of title 47, Code of Federal
Regulations, such statutes or regulations should be revised to take into
account the types of antennas that are available to consumers."

The act specifies six areas of inquiry. The relevant area for this
report is the one that relates to characteristics of consumer digital
television receivers. It states that the inquiry should

> *"consider whether ... there is a wide variation in the ability of
> reasonably-priced consumer digital television sets to receive
> over-the-air signals, such that at a given signal strength some may be
> able to display high-quality pictures while others cannot, whether
> such variation is related to the price of the television set, and
> whether such variation should be factored into setting a standard for
> determining whether a household is unserved by an adequate digital
> signal."*

The Act requires that the results and recommendations from this inquiry
be reported to the Committee on Energy and Commerce of the House of
Representatives and the Committee on Commerce, Science, and
Transportation of the Senate.

## Objectives

This report presents the results of a measurement program that was
undertaken by the Technical Research Branch of the FCC Laboratory in
order to address those portions of the SHVERA-required inquiry that
involve characteristics of consumer digital television receivers.
Accordingly, the objectives are to provide an empirical basis for
answering three questions.

\(1\) Is there a wide variation in the ability of reasonably-priced
consumer digital television sets to receive over-the-air signals, such
that at a given signal strength some may be able to display high-quality
pictures while others cannot?

\(2\) Is such variation is related to the price of the television set?

\(3\) Should such variation be factored into setting a standard for
determining whether a household is unserved by an adequate digital
signal.

## Ability to Receive Signals

The ability of a television receiver to receive over-the-air signals and
display a high quality picture is influenced by the level and quality of
the television signal reaching its antenna input terminal from the
antenna downlead, the amount of noise or interference reaching the input
terminal, and the properties of the television receiver---including the
amount of noise created by the input circuitry of the television
receiver.

### Threshold

When a television receives a signal from an [analog]{.underline} TV
station using the NTSC transmission system that has been employed in the
U.S. for decades, the TV exhibits a noisy picture at low signal levels.
The noise is frequently termed "snow". If the signal level increases,
the amount of snow in the picture decreases very gradually. If signal
level is increased until it exceeds the internally generated noise of
the television's input circuits by 34 dB (carrier-to-noise ratio =
34 dB), the picture level improves to the point that typical viewers
consider the noise to be "slightly annoying".[^3] The noise remains
perceptible but is not considered annoying at a 40-43 dB
carrier-to-noise ratio,[^4] and ceases to be visible at all when the
carrier-to-noise ratio (CNR) is 51 dB.[^5]

When a digital television receives a signal from a [digital]{.underline}
television station using the ATSC transmission system adopted by the FCC
for terrestrial DTV broadcasts in the U.S., the transition from no
picture to a virtually perfect picture occurs over a much narrower range
of signal levels. Once a threshold signal level is reached, the TV
picture is virtually perfect---limited only by the quality of the source
material and the characteristics of the television display (for example,
the picture tube and associated image forming circuits and software).
This threshold corresponds to a carrier-to-noise ratio of only about
15 dB. If the signal is reduced below this threshold value, visible
errors begin to occur in the picture---becoming more frequent with
further reductions in signal level, until the picture becomes
essentially unusable at a level only about 1 dB below the threshold.

Part of the task of determining the ability of a DTV receiver to receive
over-the-air signals is to determine this threshold when only a DTV
signal is applied to the antenna terminal (i.e., without any noise or
interfering signals), as well as when both a DTV signal and source of
electronic noise are applied simultaneously to the antenna terminal. The
resulting measured parameters are the minimum signal at the threshold of
visibility of errors (TOV) and the white noise threshold---also known as
the required carrier-to-noise ratio (CNR).

### Multipath

A propagation phenomenon called multipath causes very different effects
for analog versus digital television transmissions. Multipath is caused
by the fact that the broadcast signal may reach the television antenna
through several propagation paths that reflect off of various natural
and man-made objects. A direct signal path encountering no reflections
may also be present. The reflected signal paths are essentially delayed
versions of the direct-path signal---with the delay being dependent on
the additional distance traveled by each reflected signal.

With analog (NTSC) television, multipath causes one or more "ghost"
images displaced horizontally from the main image. (The term "ghost"
refers to the ghost-like appearance of the displaced image, which
appears as a fainter version of the primary image.) Ghosts can
significantly degrade picture quality even when the primary signal
strength is quite high. In analog television, control of ghosts is
usually accomplished by using a directional antenna oriented to
selectively receive the stronger signal (usually the direct path signal)
and to reject---at least to some extent---other paths, for which signals
typically arrive from other directions.

With digital (ATSC) television, multipath does not cause ghost-like
displaced images on the screen, though the term "ghost" is still used to
describe multipath propagation. Instead, a weak ghost may have no effect
on the picture at all. A somewhat stronger ghost may cause picture
impairments such as blockiness or freeze frames. An even stronger ghost
can completely prevent the television from decoding the digital data
necessary to produce a picture and sound. Consequently, all ATSC
television receivers contain a circuit called an equalizer, the function
of which is to adaptively cancel ghosts. If the equalizer reduces the
amplitudes of all but one signal path to a sufficiently low level, the
picture will be displayed with no impairment at all. If the cancellation
is insufficient, the TV may fail to produce a picture even when signal
level is very strong.

Equalizer performance has been one of the primary areas of technological
improvement as DTV receivers progress from one generation to the next.
With advances in equalizer technology, significant improvements have
been made in the ability to cancel larger amplitude ghosts, ghosts with
larger delays relative to the main signal, and ghost signals arriving
earlier than the main signal (in cases for which the direct path signal
is either absent or weaker than reflected signals). Other researchers
have noted a high degree of improvement in multipath-handling capability
of the latest generation of equalizer technology.[^6]

Consequently, a part of determining the ability of a DTV receiver to
receive over-the-air signals is to characterize the ability of the
receiver to handle various multipath conditions. For this study, that
characterization was performed by feeding the antenna input terminal of
the TV with signals that were recorded from television antennas at
various locations in New York City and Washington, D.C.

It is also noted that, for DTV receivers that are compliant with the
EIA/CEA-909 Antenna Control Interface specification, smart antenna
technology can mitigate the effects of multipath, as well as certain
other reception issues, through automatic optimization of various
antenna parameters such as the effective pointing direction,
polarization, and amplifier gain on a per-channel basis. The ATSC, in
its "ATSC Recommended Practice: Receiver Performance Guidelines",
recommends that "in addition to the other guidelines contained herein
for the handling of signal conditions that are experienced in the field,
consideration of a receiver-controlled antenna, as enabled by CEA-909,
is recommended" and notes that such a controllable antenna can "work in
conjunction with a receiver's equalizer, tuner, and demodulator to
improve reception under conditions of multipath and unusually weak or
strong signals."[^7] This interface was included in only one of the DTV
receivers tested for this report. Though the smart antenna functionality
was not formally tested, we observed that it did offer a user-friendly
way to optimize TV reception. Not only does it simplify the initial
setup of the DTV for the consumer, but it also provides the advantage of
instantaneously switching the antenna pointing
direction---electronically---whenever the TV channel is changed.

## Standard for Determining Whether a Household is Unserved

Section 73.622(e) of the Commission's rules, Code of Federal Regulations
(CFR) 47, specifies a method for determining the service area of a DTV
broadcast station based on OET Bulletin No. 69, *"Longley-Rice
Methodology for Evaluating TV Coverage and Interference"*---hereafter
referred to as OET‑69. The bulletin defines the method for predicting
field strength created at any given location by a television
transmitter. It further defines television reception system "planning
factors" that can be used to determine the field strength required for
successful DTV reception.

The FCC's defined reception planning factors include antenna gain,
signal loss in the down-lead cable connecting the antenna to the
television receiver, noise figure of the receiver, and required
carrier-to-noise ratio. The latter two factors are functions of the DTV
receiver and are a primary focus of the measurements conducted for this
report. These parameters, as specified by OET‑69, are shown in
Table 1‑1.

[]{#__RefHeading___Toc118693178 .anchor}Table 1‑1. Planning Factors for
DTV Reception Prediction

  ------------------------------- ------------ ---------- ---------- ----------
  **Planning Factor**             **Symbol**   **Low      **High     **UHF**
                                               VHF**      VHF**      

  Geometric Mean Frequency (MHz)  F            69         194        615

  System noise figure (dB)        N~S~         10         10         7

  Required Carrier-to-Noise ratio C/N          15.2 (15)  15.2 (15)  15.2 (15)
  (dB)                                                               
  ------------------------------- ------------ ---------- ---------- ----------

> Note: The Final Technical Report of the FCC Advisory Committee on
> Advanced Television Service listed 15.19 dB as the C/N for the Grand
> Alliance DTV receiver.[^8] In OET-69 this value is rounded to the
> nearest dB---i.e., 15 dB; however, in identifying "OET-69" planning
> factors and predictions for this report, we will round to the nearest
> tenth of a dB and use 15.2 dB. Combining this C/N value with the
> system noise figures and the ‑106.2 dBm thermal noise level specified
> in OET-69, yields a minimum signal power at TOV of ‑81.0 dBm in VHF
> and ‑84.0 dBm in UHF.

Although OET-69 was developed for defining service areas for
channel-allocation purposes, the same approach could be used for initial
prediction of whether a household is unserved by an adequate digital
signal for SHVERA purposes. Consequently, this report will evaluate the
validity of the OET-69 planning factors based on measurements of
current-model consumer DTVs.

## Overview

The laboratory-based measurements performed for this report emulated two
types of over-the-air reception conditions for DTV receivers:

> \(1\) Unimpaired signal (i.e., no multipath) \[Chapters 3 -- 5\], and
>
> \(2\) Signal impaired by multipath (ghosts) \[Chapter 6\]---focussing
> on particularly difficult multipath conditions.

The unimpaired signal measurements can be used to quantitatively predict
receiver performance under benign reception conditions---i.e., with
little multipath (commonly referred to as a white Gaussian channel). The
multipath tests provide a basis for comparing the ability of different
DTV receivers to handle difficult multipath conditions. Chapter 7 links
the new, laboratory-based measurements to earlier FCC field-test data as
a basis for anchoring the multipath results to representative,
real-world reception conditions.

#  SCOPE AND APPROACH

## Scope of Testing

The parameters measured for this report to characterize each television
receiver are as follows:

\(1\) minimum signal at the threshold of visibility of errors (TOV);

\(2\) the white noise threshold (defined at the TOV)---also known as the
required carrier-to-noise ratio (CNR); and,

\(3\) the number of ATSC-recommended field ensembles (RF captures) that
can be successfully demodulated by the receiver.

The first two of these are measures of sensitivity of the receiver for
an unimpaired signal. The latter characterizes the ability of the
receiver to handle difficult multipath conditions.

While these measurements provide a basis for achieving the stated
objectives of this report, it should be recognized that they do not
fully characterize the over-the-air reception capability of a DTV
receiver. The ATSC recommends that DTV receivers be evaluated on the
basis of a wide variety of criteria that are not included in this
report, such as multi-signal overload, tolerance to phase noise,
co-channel rejection, adjacent-channel rejection, burst noise rejection,
and a more complete characterization of multipath capability.[^9]

## Test Samples

Given the objectives of determining whether there is a wide variation in
reception performance of [reasonably-priced]{.underline} consumer
digital television receivers and determining whether the variation is
related to price of the receiver, an effort was made to select samples
over a range of prices, but with emphasis on the lower end of the price
range.

Two categories of DTV receivers were acquired for this project: digital
set-top boxes (STBs) and DTVs with integrated over-the-air ATSC tuners.
The selected receivers are standard, off-the-shelf consumer products
currently on the market.

STBs were included in the study because connection of a set-top box to
an existing television represents the lowest-cost alternative for DTV
reception. Each STB includes a digital tuner and outputs necessary to
drive high-definition television displays (through component video, DVI,
or HDMI connections) and standard-resolution analog televisions (through
a composite video output or an S-Video \[Y-C\] output). When driving a
conventional analog television, high definition programming is
down-converted to the resolution of the TV. Besides their use in
enabling digital reception with analog TVs, set-top boxes are also
useful to consumers who have high-definition, digital-ready televisions
that do not include an ATSC tuner.

### Selection Criteria

In selecting receivers for this study, several criteria were applied.

1\. A total of about 30 samples was planned for the tests in order to
balance the need for a large enough sample to provide a degree of
statistical confidence in the results with the need to limit sample size
for practical reasons.

2\. Recently introduced models were selected, where possible, especially
if the manufacturer expected a change in over-the-air digital reception
performance with the newer model; in some cases this meant requesting a
model that was not available when the tests were begun, but was
delivered late in the test cycle or, in two cases, was delivered too
late to include in this report.

3\. An attempt was made to obtain one set-top box from most companies
that manufacture one. (All set-top box models were of relatively old
designs---introduced in the year 2004 or, in one case, 2003---even
though they were the latest models available on the market.)

4\. One DTV having an integrated ATSC tuner was selected from at or near
the low-price end of each manufacturer's product line.

5\. In addition, a mid or mid-to-high priced DTV having an integrated
ATSC tuner was requested from many of the manufacturers.

### Overview of the Samples

Table 2-1 summarizes the characteristics of the DTV receivers in the
test sample. The receivers, which represent 16 brand names, are divided
by product type---set-top box versus DTV with integrated ATSC
tuner---and, within the DTV type, by price range. In most cases, prices
were determined by selecting the median price from a FROOGLE search for
each product conducted in August, 2005. Four products not found through
FROOGLE were priced through WalMart in August, 2005, and one was priced
through Amazon in September, 2005.

[]{#__RefHeading___Toc118693179 .anchor}Table 2‑2. DTV Receiver Samples

+-----------------+--------+--------+------------+-------------------+
| **Sample Type** | **     | **D    | **Display  | **Display         |
|                 | Number | isplay | Aspect     | Technology**      |
|                 | of     | Size** | Ratio**    |                   |
|                 | Sam    |        |            |                   |
|                 | ples** |        |            |                   |
+-----------------+--------+--------+------------+-------------------+
| **Set-Top Box   | 5      | N/A    | N/A        | N/A               |
| (STB)**         |        |        |            |                   |
+-----------------+--------+--------+------------+-------------------+
| **DTV with      |        |        |            |                   |
| Integrated ATSC |        |        |            |                   |
| Digital         |        |        |            |                   |
| Tuner:**        |        |        |            |                   |
+-----------------+--------+--------+------------+-------------------+
| 1.  \$370 -     | 6      | 26" -- | 4:3 or     | Direct-View CRT   |
|     \$1000      |        | 36"    | 16:9       |                   |
+-----------------+--------+--------+------------+-------------------+
| 2.  \$1001 -    | 8      | 26" -- | 16:9       | Direct-View LCD,  |
|     \$2000      |        | 52"    |            |                   |
|                 |        |        |            | Plasma,           |
|                 |        |        |            |                   |
|                 |        |        |            | CRT Rear          |
|                 |        |        |            | Projection,       |
|                 |        |        |            |                   |
|                 |        |        |            | DLP Rear          |
|                 |        |        |            | Projection,       |
|                 |        |        |            |                   |
|                 |        |        |            | LCD Rear          |
|                 |        |        |            | Projection        |
+-----------------+--------+--------+------------+-------------------+
| 3.  \$2001 -    | 9      | 32" -- | 16:9       | Direct-View LCD,  |
|     \$4200      |        | 62"    |            |                   |
|                 |        |        |            | Plasma,           |
|                 |        |        |            |                   |
|                 |        |        |            | DLP Rear          |
|                 |        |        |            | Projection,       |
|                 |        |        |            |                   |
|                 |        |        |            | LCD Rear          |
|                 |        |        |            | Projection        |
+-----------------+--------+--------+------------+-------------------+
| **TOTAL**       | **28** |        |            |                   |
+-----------------+--------+--------+------------+-------------------+

*Notes:*

*\--CRT = cathode ray tube (conventional picture tube)*

*\--DLP = digital light processing*

*\--LCD = liquid crystal display*

In order to avoid revealing specific brands or models of the samples,
test results presented in this document are reported by product type and
price categories and by a letter and number code assigned to each
product. The letter indicates product brand---with letters randomly
assigned to brand names. Within each brand, a number is assigned in
order of increasing price. For example, the designations A1, A2, and A3
represent three same-brand receivers listed in order of increasing
price.

## Test Philosophy and Approach

### Laboratory Versus Field Testing

All testing was performed in the laboratory using either
laboratory-generated signals or signals that had been digitally recorded
from television antennas at various test sites in New York City and the
Washington, DC area, and were replayed in the laboratory using equipment
that allowed the signal to translated to any desired TV channel number
for playback.

This test method offered two advantages over field-testing of the
receivers:

\(1\) the cost and time required for testing was far lower for lab-based
tests than for field testing, which would have required transporting the
bulky, heavy TVs and test equipment to multiple sites; (the TVs alone
weighed 2200 pounds and had a combined width of 82 feet), and,

\(2\) tests with signals that are generated or recreated (by playback)
in the laboratory are expected to yield more consistent results than are
field tests, in which received signal characteristics may vary
significantly over the course of testing 28 receivers.

### TV Channel Selection

For testing minimum signal at TOV, channels 3, 10, and 30 were selected
to represent the low-VHF, high-VHF, and UHF bands, respectively.
Selection was based on relatively central locations within the
respective bands and an absence of local TV broadcasts on these
channels.

Other tests, for which results were not expected to vary with channel,
were performed on TV channel 30.

### Operation and Connection of Samples

For receivers having multiple antenna inputs that could handle ATSC
signals, only the input labeled "antenna A" or "antenna 1" was tested.
For receivers having a radio frequency (RF) output associated with the
selected antenna input, the output was externally terminated in 75 ohms.

Each set-top box was operated in a high definition mode and was
connected to a high definition monitor by means of a component video
output.

### Test Configurations

All test and measurement setups maintained a 50-ohm impedance
throughout, except at the signal source and the consumer TV inputs,
which were each specified to be nominally 75 ohms. (An older,
instrumented reference receiver included in one test had a 50-ohm input
impedance.) The 75‑ohm devices were matched to the rest of the test
setup through impedance-matching pads, except that, for one of the test
setups, an impedance transformer was used at the signal source to reduce
losses. In addition to the impedance-matching pads, 50-ohm attenuator
pads were used at various places throughout the test setups to reduce
the effects of any impedance mismatches at places where such mismatches
were considered likely or would be expected to have a significant
impact.

The minimum signal at TOV is the only measured parameter for which
absolute accuracy of the measurement equipment was a factor;
consequently, that parameter was tested by connecting a signal
source---through appropriate pads, step attenuators, and cables---to one
TV at a time. After adjusting the signal attenuation to achieve TOV on
the TV, the output of the entire setup---with the exception of the final
impedance-matching pad, was connected to a vector signal analyzer for
measurement of the signal level. The only correction then necessary to
determine the input to the TV was to subtract the attenuation of the
impedance-matching pad from the measured level. That attenuation was
measured separately.

For the measuring white noise threshold (required CNR), absolute
measurement accuracy was less critical since the value to be determined
was the ratio of a signal level to a noise level. To maintain accuracy
of the ratio, both measurements were made with the vector signal
analyzer on the same amplitude range. The reduced criticality of
absolute measurement accuracy enabled the use of a splitter to
simultaneously deliver the signal and noise to as many as eight TVs and
to the vector signal analyzer for the quantitative measurements. The
simultaneous connection reduced measurement time by allowing TV channel
scans (required by many of the TVs when a signal was changed) to be
performed simultaneously on multiple TVs and by reducing the need to
repeatedly disconnect and reconnect cables.

Tests of the ability of each receiver to handle the multipath conditions
represented by the ATSC-recommended field ensembles (RF captures) also
did not require absolute accuracy in measuring the applied signal
levels; consequently, the same splitter arrangement was used. The
approach was to apply a signal level well above the minimum signal level
at TOV (by about 50 dB) so that signal level was not an issue.

Details on the test methods and configurations are presented in Appendix
A.

### Thresholds

For both types of threshold measurements (required CNR and minimum
signal at TOV), the reported value is the level measured on the maximum
attenuation step (lowest signal level) that resulted in no observed
errors in 60 seconds of viewing time. The threshold level at which the
60-second viewing time condition was met was nominally somewhere between
that reported level and the next higher attenuation level (next lower
signal level step); consequently, this approach can be expected to
overestimate required signal levels by an average of half the attenuator
step size of 0.1 dB. One could therefore justify subtraction of 0.05 dB
from the measured signal levels. This subtraction was not performed, in
part to compensate for the fact that TOV measurements are often based on
longer observation times than the 60 seconds used in these tests.

#  WHITE-NOISE THRESHOLD MEASUREMENTS (REQUIRED CARRIER-TO-NOISE RATIO)

White-noise threshold refers to the ratio of signal ("carrier") power to
noise power within the 6-MHz bandwidth of a television channel when both
an unimpaired signal (no multipath) and broadband ("white") Gaussian
noise are simultaneously applied to the antenna terminal of a DTV
receiver and the signal or noise power is adjusted to the point at which
observable errors in the DTV picture just become invisible---i.e., the
threshold of visibility (TOV). This is the carrier-to-noise ratio (CNR)
required to produce a "clean" DTV picture. The definition assumes that
the applied noise power is sufficiently higher than any noise generated
internally by the DTV receiver circuitry so as to make the internally
generated noise negligible.

At CNR levels below the white-noise threshold, picture quality rapidly
degrades to the point that, only about one dB below the white-noise
threshold, the picture is typically unwatchable or nonexistent.

At CNR levels above the white-noise threshold, the picture is
essentially free of defects that are related to transmission and
reception of the signal.

White noise threshold is of direct interest because it indicates the
ability of a digital television to receive and process a DTV signal in
the presence of high ambient noise levels---assuming that the signal is
not significantly impaired by multipath or interference and that the
ambient noise has characteristics similar to white Gaussian noise. In
cases where the ambient environment is quiet, white noise threshold is
useful in understanding the reception performance of a DTV receiver in
the presence of noise that is internally generated within the input
circuits of the receiver.

The results of this chapter apply only to signals that are unimpaired by
multipath. In the presence of multipath, a higher CNR may be required to
produce a clean picture. While the measurements performed for this
report do not address such an increase, the topic is discussed in
Chapter 7, based on earlier field test results.

## Measurement Method

White-threshold of each receiver was measured by simultaneously
injecting into the antenna port of the receiver both an unimpaired
(e.g., no multipath) ATSC signal on channel 30 and white noise from a
noise generator. A nine-way splitter feeding equal-length,
well-shielded, low-loss cables allowed the same combination of signal
plus noise to be applied simultaneously to as many as eight DTV
receivers and a vector signal analyzer that was used for the
measurements. As a consistency check, receiver D3 was included in each
group of eight receivers that were tested; measurements of D3 were
consistent within ±0.1 dB.

Impedance-matching attenuator pads (50 ohms to 75 ohms, 5.8 dB power
attenuation) at each TV receiver served to match the nominal 75-ohm
impedance of the receiver antenna ports to the rest of the 50-ohm
measurement system and, through the attenuation it provided, served to
reduce the impact of any deviations from that nominal TV input
impedance. At the vector signal analyzer, a 6-dB, 50-ohm attenuator
served a similar function.

Because the small differences in loss between the various splitter
outputs, cables, and pads can be expected to equally affect both the
signal and the noise, the measured CNR is not affected by such
differences.

The signal source for these tests was an RF player (Sencore RFP-910)
playing the "Hawaii_ReferenceA" file supplied with the player. The file
consisted of a 25-second repeating loop of motion video scenes shot at
several outdoor locations. At each loop restart, most DTV receivers
exhibited video errors related to re-locking to the signal;
consequently, the first three seconds of each loop were not included in
the observation time. (An ATSC signal generator, rather than the RF
player, had been intended for these tests. Use of the generator would
have avoided issues with loop restart time, but the generator was
abandoned due to degraded signal quality.) The signal was amplified
before splitting it. A step attenuator following the amplifier was used
to adjust the signal level.

The noise source was a noise generator (Noise/Com UFX-7110) band limited
to 700 MHz, well above the frequency of TV channel 30, thus leaving the
spectrum flat across the bandwidth of the selected TV channel. The
injected noise power was set nominally to -70 dBm within the 6-MHz
bandwidth of channel 30---about 29 dB above the internally generated
noise of a typical DTV receiver---by using a step attenuator with 0.1-dB
steps. The noise power measurement (usually within 0.05 dB of -70 dBm)
was then recorded. The actual injected noise power was computed by
subtracting the effect of instrument noise, which was about 26 dB below
the injected noise power.

Signal level was increased in 0.1-dB steps until the TV picture could be
viewed for 60 seconds without observing a video error (excluding loop
restart periods, as noted above). A measurement was then made of the
combined power of both the injected signal and the injected noise, and
the signal power was computed by subtracting the noise power (in linear
power units); since the noise power at the threshold was typically about
15 dB below the signal, the net signal power was only about 0.1 dB below
the measured total power.

Further details on the measurement procedure are contained in Appendix
A.

## Format of The Bar Graph Data

The measurement results are presented in bar-graph form in Figure 3-1.
That format, explained here, is also used in subsequent chapters to
present other results.

Each bar on the graph represents performance of one DTV receiver. The
"Better"/"Worse" labels on the vertical axis indicate that, for the
plotted parameter, lower values represent better performance.

Each receiver is designated by a letter and a numeral. The letters,
which were assigned randomly, represent brand names. Thus, receivers A1,
A2, and A3 are all of the same brand.

The receivers are grouped into categories. The first category is set-top
boxes (STBs). The remaining categories are three different price ranges
of DTVs. Within each group, the results are listed in order of the
randomly assigned brand code letters rather than in price order. This
approach was taken so that individual products could not be identified
based on price.

The solid blue line represents the median result across all tested
receivers. The dashed blue line represents the median result within each
category. The dashed red line represents the mean result within each
category. A wider dashed green line represents the value of the planning
factor assigned to the measured parameter by OET-69.

## Results

The results of the white-noise threshold measurements are shown in
Figure 3-1.

### Nominal Performance and Variation Among Samples

Statistics of the white-noise threshold (required CNR) are shown in
Table 3-1. The white noise threshold of the median receiver---measured
across all tested receivers---is 15.3 dB. This is only 0.1 dB above
(worse than) the corresponding planning factor value in OET-69. (Because
the CNR was determined from the ratio of two power measurements
performed on the same amplitude range of the same measuring instrument,
it's value is not affected by absolute calibration accuracy of the
instrument and is therefore expected to be accurate to within
0.2 dB.[^10])

[]{#__RefHeading___Toc118693180 .anchor}Table 3‑3. Statistics of White
Noise Threshold

  ------------------------------------------------------------ ----------
  **WHITE NOISE THRESHOLD**                                    

  Median across all receivers (dBm)                            15.3

  Median re OET-69 planning factors                            0.1

  Deviations of receivers from median (dB)                     

  \--Best performing receiver (dB)                             -0.4

  \--Worst performing receiver (dB)                            0.5

  \--89th percentile receiver (dB)                             0.3

  Standard deviation (dB)                                      0.2

  Total span from best to worst receiver (dB)                  0.8[^11]
  ------------------------------------------------------------ ----------

The variations among receivers were quite small. The standard deviation
of the CNR measurements across all receivers was 0.2 dB. The total span
from best to worst performing receiver was 0.8 dB, with the worst
measured white noise threshold being 0.5 dB above the median value.

### Variation with Price and Type Category

#### Magnitude of Observed Variations With Product Type and Price {#magnitude-of-observed-variations-with-product-type-and-price .unnumbered}

The observed performance variations among the product type and price
categories were also small, as shown in Table 3-2. The least expensive
way to receive a DTV broadcast is to purchase a digital set-top box and
connect it to an existing TV. Median performance of set-top boxes was
only 0.1 dB worse than the overall median. The median low-cost and
mid-cost DTVs performed at the overall median, and the median high-cost
DTV performance was 0.2 dB better than the overall median.

[]{#__RefHeading___Toc118693181 .anchor}Table 3‑4. Product-Type/Price
Variations of White Noise Threshold

  ---------------------------------------------------------------- ------
  **WHITE NOISE THRESHOLD**                                        

  Median of Set-Top Boxes re Overall Median (dB)                   0.1

  Median of Low-Price DTVs re Overall Median (dB)                  0.0

  Median of Medium-Price DTVs re Overall Median (dB)               0.0

  Median of High-Price DTVs re Overall Median (dB)                 -0.2
  ---------------------------------------------------------------- ------

#### Statistical Significance of Observed Variations With Product Type and Price {#statistical-significance-of-observed-variations-with-product-type-and-price .unnumbered}

Apparent variations in performance of samples with price can be caused
by random sampling effects even when there is no underlying
performance/price dependence in the overall population; hence, some
means is necessary to determine whether an apparent dependence observed
in the sample is statistically significant.

In the case of measurements of the required CNR for the tested
collection of DTV receivers, the observed variations with price are so
small as to be inconsequential; consequently, assessing the statistical
validity of those variations is hardly necessary. Nonetheless, an
analysis is included here for completeness and to provide a comparative
basis for more significant observed variations that are presented in
subsequent chapters.

As seen in Table 3-3, the Pearson's correlation coefficient between
required CNR and receiver price was computed as -8.6 percent when all
receivers were included and +7.0 percent when only the DTVs (not set-top
boxes) were included. A negative sign indicates that the required CNR
appears to decrease (i.e., improve) with increasing receiver price,
while a positive sign indicates that the required CNR increases (i.e.,
degrades) with increasing price. Determining whether any observed
apparent trend is real or is an artifact of the small sample set used in
the tests requires a statistical assessment.

[]{#__RefHeading___Toc118693182 .anchor}Table 3‑5. Correlation
Coefficient of White Noise Threshold with Price

  ---------------------------------------------------------- ------------
  **Pearson's Correlation Coefficient of White Noise         
  Threshold with Price**                                     

  All Tested Receivers                                       -8.6%

  DTVs Only (no Set-Top Boxes)                               +7.0%
  ---------------------------------------------------------- ------------

The usual method of assessing the statistical significance of given
value of the Pearson's correlation coefficient is to compare the
magnitude of the observed correlation to values in a table of critical
values of the Pearson's correlation coefficient. The technique is used
to determine the likelihood that a correlation as high as that which was
observed might occur randomly, for the selected sample, if there is no
actual correlation between required CNR and receiver price in the larger
population of all DTV receivers. Such a lookup table specifies values as
a function of the "number of degrees of freedom", which is two less than
the total number of samples---*assuming that the samples are
independent*.

For the overall sample size used in this study (28 samples, 26 degrees
of freedom), one can determine from such a table that the magnitude of
an observed correlation coefficient must be 32 percent or higher in
order to ensure that there is no more than a five percent probability
that the observed correlation could result by random sampling effects
from a larger population that has no such correlation. In the case of
the 23 DTVs (i.e., excluding the set-top boxes), the magnitude of an
observed correlation would have to be 35 percent or higher to meet the
same criterion. (These are single-sided probabilities---i.e., the
probability that a correlation magnitude will exceed, in a single
direction, a given correlation value. For example, if the overall
population has no correlation with price, there is a five percent
probability that the correlation of a randomly selected sample of 28
receivers will exceed a 32 percent magnitude with a negative
correlation---indicating [decreasing]{.underline} CNR with increasing
receiver price. There is also a five percent probability of exceeding
that same magnitude with a positive correlation---indicating
[increasing]{.underline} CNR with increasing price.)

It should be noted that these statistical calculations are dependent
upon a number of assumptions, including that the shape of the
probability distribution of the measured parameter is normal (Gaussian),
that the samples were randomly selected, and that the samples are
independent. None of these assumptions is strictly true for the case at
hand. Of particular concern is the independence assumption, because it
is quite likely that some of the receiver samples share critical
subsystems. For example, a given tuner or demodulator design may be used
in more than one of the receivers. The effect of such a commonality
between samples would be to decrease the effective number of degrees of
freedom in the computed Pearson's correlation coefficient. Such a
decrease would increase the magnitude of correlation that would have to
be observed to have a given confidence level in the result.

The observed correlations of -8.6 percent and +7.0 percent in the
white-noise threshold measurements are so small as to provide no
confidence that the small observed variations in performance with price
reflect a real price-dependence in the overall population of DTV
receivers currently on the market.

### Effect of TV Channel

White noise threshold (required CNR) is expected to be dependent on the
demodulator function of a DTV receiver. Since this function occurs after
the tuner heterodynes the incoming RF signal from the frequency band of
the TV channel to an intermediate frequency (IF), one would expect the
white noise threshold to be essentially independent of TV channel
number. Consequently, testing was performed on only one
channel---channel 30.

In testing minimum signal level of the DTV receivers, as reported in the
next chapter, there was a large variation in the results between
channels for some TVs. In order to verify that the variation was not
related to changes in white noise threshold, the white noise threshold
of one DTV receiver was also tested on channel 3. The selected receiver
was G2, the receiver with the largest variation in minimum signal level
across the channels (a 13 dB difference between channels 3 and 30). For
this receiver, the measured white noise thresholds on channels 3 and 30
were 15.6 and 15.5 dB, respectively; this difference is within
measurement error.

![](media/image1.wmf){width="6.497916666666667in" height="4.3in"}

[]{#__RefHeading___Toc118693135 .anchor}Figure 3‑1. Measured White Noise
Threshold of Receivers

#  MINIMUM INPUT SIGNAL MEASUREMENTS

Minimum input signal at the threshold of visibility (TOV) is the signal
("carrier") power at the antenna terminal of a DTV receiver when the
signal level is adjusted to the point at which observable errors in the
DTV picture just become invisible. It is a direct measure of sensitivity
of a DTV receiver to weak signals in the absence of significant
externally generated noise or interference---assuming that the input
signal is not significantly impaired by multipath. At input levels below
this threshold level, picture quality rapidly degrades to the point
that, only about one dB below the white-noise threshold, the picture is
typically unwatchable or nonexistent. At input levels above the
threshold, the TV picture is essentially free of defects that are
related to transmission and reception of the signal.

The results of this chapter apply only to signals that are unimpaired by
multipath or interference. In the presence of multipath, a higher signal
level may be required to produce a clean picture. While the measurements
performed for this report do not address such an increase, the topic is
discussed in Chapter 7, based on earlier field test results.

## Measurement Method

Because minimum input signal at TOV is an absolute measurement rather
than a ratio, the splitter was not used for these tests. The receivers
were tested sequentially in groups of about eight---with receiver D3
included in each group, as a consistency check; measurements of D3 were
consistent within ±0.3 dB. The results are subject to the absolute
measurement accuracy of the vector signal analyzer, which is specified
as ±1.5 dB maximum and ±0.5 dB typical on the amplitude range that was
used for the measurements;[^12] additional errors due to adjustment for
attenuation of impedance-matching pad---as described below---are
expected to be negligible compared to the VSA tolerance.

The tests were performed on three TV channels---3, 10, and 30---in order
to evaluate performance in the low VHF, high VHF, and UHF bands,
respectively. The selection of those specific channels was based on
avoiding local broadcast channels and selection of a relatively central
channel within each band.

The signal source for these tests was an RF player (Sencore RFP-910)
playing the "Hawaii_ReferenceA" file supplied with the player. The file
consisted of a 25-second repeating loop of motion video scenes shot at
several outdoor locations. At each loop restart, many DTV receivers
exhibited video errors related to re-locking to the signal;
consequently, the first three seconds of each loop were not included in
the observation time. A step attenuator was used to adjust the signal
level. The signal was applied to a single DTV receiver through a
low-loss 50-ohm cable followed by a 10-dB attenuator pad and an
impedance-matching attenuator pad having 5.8 dB power attenuation. The
latter served to match the nominal 75-ohm impedance of the receiver
antenna port to the rest of the 50-ohm measurement system. Both pads
served to minimize reflections that might be caused by any deviation of
receiver input impedance from the nominal.

Signal level was increased in 0.1-dB steps until the TV picture could be
viewed for 60 seconds without observing a video error (excluding loop
restart periods, as noted above). The low-loss cable and 10-dB pad were
then connected to a vector signal analyzer on its most sensitive
amplitude range (-50 dBm) to measure the power of the applied signal.
The 10-dB pad served to minimize reflections that would be caused by any
deviation of the vector signal analyzer input impedance from 50 ohms. A
separate measurement of instrument noise (typically about 19 dB below
the measured signal level) was subtracted---in linear power units---from
the measured power level to remove the very minor effects of vector
signal analyzer self noise from the measurement. The attenuation of the
impedance matching pad, which was connected to the TV input but not to
the vector signal analyzer, was then subtracted (in dB) from the result
to determine the signal level that had been applied to the DTV receiver
antenna port. The presence of that pad at the TV input but not at the
spectrum analyzer input served a dual purpose---matching the respective
input impedances of the two devices and providing a 5.8 dB signal
advantage to the vector analyzer to minimize the impact of the vector
signal analyzer self noise.

Further details on the measurement procedure are contained in Appendix
A.

## Results

The results of the minimum signal level measurements for the three
tested channels are shown in Figure 4‑1. Individual results for TV
channels 3, 10, and 30 are shown in Figures 4-2, 4-3, and 4-4,
respectively. The general format of the plots is as described in
Chapter 3 in the section titled, "Format of the Bar Graph Data", except
that, in the case of Figure 4-1, there are three bars per DTV
receiver---representing the three channels tested. Also, note the
differences in vertical scales among the four graphs.

### Nominal Performance and Variation Among Samples

Table 4-1 shows the statistical properties of the measurements of
minimum signal level at TOV.

[]{#__RefHeading___Toc118693183 .anchor}Table 4‑6. Statistics of Minimum
Signal Level at TOV

  ------------------------------------------ -------- --------- ---------
  **MINIMUM SIGNAL LEVEL AT TOV**            **Chan   **Chan    **Chan
                                             3**      10**      30**

  Median across all receivers (dBm)          -82.2    -83.2     -83.9

  Median re OET-69 planning factors          -1.2     -2.2      0.1

  Deviations of receivers from median (dB)                      

  \--Best performing receiver (dB)           -2.5     -1.7      -1.4

  \--Worst performing receiver (dB)          12.5     4.3       2.5

  \--89th percentile receiver (dB)           5.1      3.1       1.3

  Standard deviation (dB)                    3.7      1.6       0.9

  Total span from worst to best receiver     15.0     6.0       3.9
  (dB)                                                          
  ------------------------------------------ -------- --------- ---------

The median minimum signal level at TOV across all measured receivers was
found to decrease slightly with increasing channel number---with channel
3 requiring a 1.7‑dB higher signal than channel 30. The measured median
values match---within 1 dB---the -83 dBm minimum performance standard
recommended by the ATSC.[^13]

The median required signal levels were slightly better---by 1.2 dB and
2.2 dB, respectively---than that predicted for the VHF-low and VHF-high
bands using the OET-69 planning factors (-81.0 dBm) and closely matched
the predictions for channel 30 (-84.0 dBm).[^14] On channel 3, only 21
percent of the tested receivers performed more poorly in minimum signal
level than the performance modeled in OET-69 by an amount exceeding
1-dB---the approximate tolerance of the measurements.[^15] On channels
10 and 30, the numbers are 11 percent and 18 percent, respectively.

The variation among receivers was large on channel 3---with a 3.7‑dB
standard deviation. The two receivers exhibiting poorest performance
performed at levels 10.6 and 12.5 dB worse than the median. Those two
receivers---both the same brand---are responsible for much of the
observed variability; omitting them from the calculations reduces the
standard deviation to 2.3 dB. The third worst performer was 6.7 dB above
the median. 89 percent of the receivers (all but three) were within
5.1 dB of the median.

Variations were relatively small on channels 10 and 30. Standard
deviation across all receivers was 1.6 dB on channel 10 and 0.9 dB on
channel 30. The worst performers differed from the median by 4.3 and 2.5
dB, respectively, on channels 10 and 30, and 89 percent of the receivers
(all but three) were no more than 3.1 dB above (worse than) the median
on channel 10 and no more than 1.3 dB above (worse than) the median on
channel 30.

### Variations With TV Channel For One Sample

At least two TVs exhibited a much larger than expected variation in
reception performance---as measured by minimum signal level at
TOV---between the three tested TV channels. In order to further
characterize this variation, the receiver exhibiting the largest
variation between channels (receiver G2) was further tested to determine
minimum signal at TOV for each of the 12 VHF channels and for three UHF
channels. The results, shown in Figure 4‑5, indicate that the receiver
exhibits poor sensitivity throughout the low-VHF band (channels 2
through 6), but good sensitivity throughout the high-VHF band (channels
7 through 13) and the UHF band. On average, the high-VHF and UHF
performance is 13 dB better than the low-VHF performance. The reason for
this performance difference is not known.

The apparently abrupt change in sensitivity occurring between channels 6
and 7 is easier to understand if the data is plotted as a function of
frequency, as in Figure 4‑6. It can be seen that there is a large gap in
frequency between TV channels 6 and 7, and that the increase in minimum
signal at TOV that occurs in moving from the high-VHF band (channels
7-13) to the low-VHF band (channels 2-6) appears to actually begin, to a
small degree, in the lower portion of the high-VHF band. (Note that the
measured data is indicated by square symbols and measured points are
connected by straight lines.)

### Variation with Price and Type Category

#### Magnitude of Observed Variations With Product Type and Price {#magnitude-of-observed-variations-with-product-type-and-price-1 .unnumbered}

As can be seen in Table 4-2, the observed variations in minimum signal
level at TOV with product type and price categories were very small for
channels 10 and 30 (category medians differing from overall median by
less than 1 dB) and were somewhat larger for channel 3. On channel 3,
median performance of set-top boxes was 2.0 dB worse than the overall
median of all receivers and the best median performance was achieved by
the low-price DTV category, which slightly outperformed the medium and
high-priced categories. Most of the differences in median values between
categories are so small as to be considered insignificant, and even the
largest differences would influence reception performance only in
locations where the signal margin is very small.

[]{#__RefHeading___Toc118693184 .anchor}Table 4‑7. Product-Type/Price
Variations of Minimum Signal at TOV

  --------------------------------------------- -------- -------- --------
  **MINIMUM SIGNAL LEVEL AT TOV**               **Chan   **Chan   **Chan
                                                3**      10**     30**

  Median of Set-Top Boxes re Overall Median     2.0      0.5      0.7
  (dB)                                                            

  Median of Low-Price DTVs re Overall Median    -1.1     -0.2     -0.2
  (dB)                                                            

  Median of Medium-Price DTVs re Overall Median 0.0      0.5      0.0
  (dB)                                                            

  Median of High-Price DTVs re Overall Median   -0.7     -0.3     0.0
  (dB)                                                            
  --------------------------------------------- -------- -------- --------

#### Statistical Significance of Observed Variations With Product Type and Price {#statistical-significance-of-observed-variations-with-product-type-and-price-1 .unnumbered}

Table 4-3 shows the Pearson's correlation coefficient between the
minimum signal at TOV and the price of each DTV receiver. Random
sampling effects can lead to apparent correlations in a given collection
of DTV receivers even if the overall DTV population of receivers on the
market exhibits no such correlation; consequently, a statistical
assessment must be performed in order to judge whether the observed
correlation reflects an actual correlation in overall population or is
simply an artifact of sampling.

[]{#__RefHeading___Toc118693185 .anchor}Table 4‑8. Correlation
Coefficient of Minimum Signal at TOV with Price

  ----------------------------------------- --------- ---------- ----------
  **Pearson's Correlation Coefficient of    **Chan    **Chan     **Chan
  Minimum Signal at TOV with Price**        3**       10**       30**

  All Tested Receivers                      -14.3%    -4.9%      +3.9%

  DTVs Only (no Set-Top Boxes)              -0.3%     +0.4%      +12.3%
  ----------------------------------------- --------- ---------- ----------

Chapter 3 explains the methods and pitfalls of such a statistical
assessment. Using typical assumptions, one would conclude that an
observed correlation coefficient with a magnitude of 32 percent or
higher is unlikely to occur (less than five percent probability) in a
sample size of 28 (the total number of receivers tested for this report)
if there is no correlation in the overall population. Similarly, with a
sample size of 23 (the number of DTVs---excluding set-top boxes---tested
for this report), a correlation coefficient magnitude of 35 percent or
higher is unlikely to occur if there is no correlation in the overall
population. Thus, we would conclude that an observed correlation is
statistically significant only if its magnitude exceeds the appropriate
one of these thresholds.[^16]

None of the price/performance correlations found here come even close to
the threshold for statistical significance. Thus, the measurements of
minimum signal at TOV show no statistically significant correlation of
performance with price.

![](media/image2.wmf){width="6.497916666666667in"
height="4.254166666666666in"}

[]{#__RefHeading___Toc118693136 .anchor}Figure 4‑2. Measured Minimum
Signal Level at TOV on Three Channels

![](media/image3.wmf){width="6.497916666666667in"
height="4.267361111111111in"}

[]{#__RefHeading___Toc118693137 .anchor}Figure 4‑3. Measured Minimum
Signal Level at TOV on Channel 3 (Low VHF)

![](media/image4.wmf){width="6.497916666666667in"
height="4.2868055555555555in"}

[]{#__RefHeading___Toc118693138 .anchor}Figure 4‑4. Measured Minimum
Signal Level at TOV on Channel 10 (High VHF)

![](media/image5.wmf){width="6.497916666666667in"
height="4.2868055555555555in"}

[]{#__RefHeading___Toc118693139 .anchor}Figure 4‑5. Measured Minimum
Signal Level at TOV on Channel 30 (UHF)

![](media/image6.wmf){width="6.497916666666667in"
height="4.222222222222222in"}

[]{#__RefHeading___Toc118693140 .anchor}Figure 4‑6. Measured Minimum
Signal Level at TOV Versus Channel for Receiver G2

![](media/image7.wmf){width="6.497916666666667in"
height="4.222222222222222in"}

[]{#__RefHeading___Toc118693141 .anchor}Figure 4‑7. Measured Minimum
Signal Level at TOV Versus Frequency for Receiver G2

#  INFERRED NOISE FIGURE

The minimum signal level at TOV, presented in Chapter 4, can be viewed
as the combined effect of two properties of the DTV receiver: the
internal noise created by the receiver's input circuitry and the CNR
required to produce a clean picture. Separating the measurement into
those two basic terms provides a better understanding of the differences
in performance between DTV receivers. It should be noted that this
breakout is strictly valid only when reception sensitivity is limited by
the receiver's amplifier noise, which we anticipate to be true for most
receivers; however, if other factors limit reception sensitivity, the
"inferred" receiver noise calculations in this chapter reflect those
other performance limitations rather than actual receiver noise.[^17]

The internal noise created by a receiver is often expressed in terms of
noise figure. The noise figure of a receiver is the effective amount of
noise created by the input circuitry of the receiver, measured relative
to a physical limit on noise known as thermal noise and referenced to
the input of the receiver. While noise figure cannot be directly
measured externally, the effective noise figure can be inferred from the
required CNR measurements of Chapter 3 in conjunction with the minimum
signal level at TOV, as measured in Chapter 4.

Figure 5-1(a) illustrates measurement of required CNR (i.e., white noise
threshold). The vertical line represents a range of signal and noise
amplitudes that could be applied to the antenna terminal of a TV
receiver. With external white noise added at a level well above the
internal noise of the receiver, signal levels in the lower, red portion
of the line will result in no TV picture. Signals in the yellow range
will produce a picture degraded by demodulation errors. Signals in the
green range, with signal level exceeding the noise level by an amount
greater than the required CNR, will produce a picture free of
reception-related defects. (The carrier-to-noise [ratio]{.underline}
(CNR), becomes a difference rather than a ratio, because of the
logarithmic scaling implied by measurements in decibels.)

Figure 5-1(b) illustrates measurement of minimum signal at TOV, the
minimum signal level required to achieve a clear picture absent any
external noise. Assuming that the TV reception is limited by the
receiver's broadband internal noise, this minimum signal level can be
viewed as the sum (in dB) of two parameters---the internally generated
noise level of the DTV receiver and the amount by which the signal must
exceed that noise level, i.e., the required CNR. The noise level of the
receiver can be expressed as the sum (in dB) of the noise figure of the
receiver and the thermal noise at some reference temperature. Thus, we
have

*Minimum Signal at TOV (dBm) = Thermal Noise (dBm) + Noise Figure (dB) +
Required CNR (dB)*

Thermal noise is a function only of reference temperature and
measurement bandwidth and is given by

*Thermal Noise (dBm) = 10 log(k T B) + 10 log(1000 mW/W)*

where

*k = Boltzmann's constant = 1.38065 x 10^-23^ joules/°K*

*T = reference temperature in degrees Kelvin (290°K for this
report)*[^18]

*B = the measurement bandwidth = 6,000,000 Hz for a television channel*

*10 log(1000 mW/W) provides the conversion from dBWatts to dBmilliwatts*

Using the above values, thermal noise = -106.2 dBm.

If the noise generated internally by the DTV receiver is similar to
white Gaussian noise, then the required CNR in Figure 5-1(a) is the same
as that in Figure 5-1(b); consequently, noise figure of the receiver can
be computed as\
\
*Noise Figure (dB) = Minimum Signal at TOV (dBm) -- Required CNR (dB) --
Thermal Noise (dBm)*

## Results

The noise figures for all tested receivers on the three tested channels
have been computed as above and are shown in Figure 5-2. Individual
results for TV channels 3, 10, and 30 are shown in Figures 5-3, 5-4, and
5-5, respectively. The general format of the plots is as described in
Chapter 3 in the section titled, "Format of the Bar Graph Data", except
that, in the case of Figure 5-2, there are three bars per DTV
receiver---representing the three channels tested. The reader should
note the differences in vertical scales among the four graphs.

Note that in performing the noise figure calculation, the required CNR
is assumed to be constant across the TV channels for the reasons
discussed in the "Effect of TV Channel" section of Chapter 3. Thus, the
CNR measurements on channel 30 are applied to channels 3 and 10, as
well.

### Nominal Noise Figure and Variation Among Samples

Table 5-1 shows the statistical properties of the noise figure across
all tested receivers.

[]{#__RefHeading___Toc118693186 .anchor}Table 5‑9. Statistics of
Receiver Noise Figure

  --------------------------------------------- -------- -------- --------
  **NOISE FIGURE**                              **Chan   **Chan   **Chan
                                                3**      10**     30**

  Median across all receivers (dB)              8.8      7.6      6.9

  Median re OET-69 planning factors             -1.2     -2.4     -0.1

  Deviations of receivers from median                             

  \--Best performing receiver (dB)              -2.5     -1.3     -1.3

  \--Worst performing receiver (dB)             12.2     4.5      2.6

  \--89^th^ percentile receiver (dB)            4.5      3.3      1.2

  Standard deviation (dB)                       3.6      1.6      0.9

  Total span from worst to best receiver (dB)   14.7     5.7      3.9
  --------------------------------------------- -------- -------- --------

The median noise figure across all measured receivers was found to
decrease with channel---with the noise on channel 30 being 1.9 dB lower
than that on channel 3. The median noise figures were 1.2 to 2.4 dB
better than those shown in the OET-69 planning factors for the VHF bands
(10 dB) and essentially matched the planning factor for the UHF band
(7 dB).

On channel 3, only 21 percent of the tested receivers performed more
poorly in noise figure than the value modeled in OET-69 by an amount
exceeding 1-dB---the approximate tolerance of the measurements.[^19] On
channels 10 and 30, the numbers are 7 percent and 18 percent,
respectively.

The variations among receivers were large on channel 3---with a 3.6 dB
standard deviation and two receivers performing at levels 10.3 and
12.2 dB worse than the median. More attention to tuner design for those
two receivers might significantly improve performance in weak signal
conditions. 89 percent of the receivers (all but three) were no more
than 4.5 dB above (worse than) the median noise figure.

Variations were relatively small on channels 10 and 30. Standard
deviation across all receivers was 1.6 dB on channel 10 and 0.9 dB on
channel 30. The worst performers differed from the median by 4.5 and 2.6
dB, respectively, on channels 10 and 30, and 89 percent of the receivers
(all but three) were no more than 3.3 dB above (worse than) the median
noise figure on channel 10 and no more than 1.2 dB above the median
noise figure on channel 30.

### Variation With Product Type and Price

#### Magnitude of Observed Variations With Product Type and Price {#magnitude-of-observed-variations-with-product-type-and-price-2 .unnumbered}

As can be seen in Table 5-2, the observed variations in receiver noise
figure with product type and price categories were very small (category
medians differing from overall median by less than 1 dB) for channels 10
and 30 and were somewhat larger for channel 3. On channel 3, median
noise figure of set-top boxes was 1.7 dB worse than the overall median
of all receivers. The best median noise figure---1.4 dB better than the
overall median---occurred in the low-price DTV category. Such
differences are likely to influence performance only in locations where
the signal margin is very small.

[]{#__RefHeading___Toc118693187 .anchor}Table 5‑10. Product-Type/Price
Variations of Receiver Noise Figure

  ----------------------------------------------- -------- -------- --------
  **NOISE FIGURE**                                **Chan   **Chan   **Chan
                                                  3**      10**     30**

  Median of Set-Top Boxes re Overall Median (dB)  1.7      0.1      0.6

  Median of Low-Price DTVs re Overall Median (dB) -1.4     -0.1     0.0

  Median of Medium-Price DTVs re Overall Median   0.0      0.4      -0.1
  (dB)                                                              

  Median of High-Price DTVs re Overall Median     -0.8     -0.3     0.0
  (dB)                                                              
  ----------------------------------------------- -------- -------- --------

#### Statistical Significance of Observed Variations With Product Type and Price {#statistical-significance-of-observed-variations-with-product-type-and-price-2 .unnumbered}

Table 5-3 shows the Pearson's correlation coefficient between the noise
figure and the price of each DTV receiver. Given the similarity of
results with those for minimum signal at TOV, the reader is referred to
Chapter 4 for a discussion of the interpretation of these results. The
bottom line is that there is no statistically significant correlation of
noise figure with price of the receivers..

[]{#__RefHeading___Toc118693188 .anchor}Table 5‑11. Correlation
Coefficient of Receiver Noise Figure with Price

  ----------------------------------------- -------- ---------- ----------
  **Pearson's Correlation Coefficient of    **Chan   **Chan     **Chan
  Noise Figure with Price**                 3**      10**       30**

  All Tested Receivers                      -14%     -4%        +6%

  DTVs Only (no Set-Top Boxes)              -1%      -1%        +11%
  ----------------------------------------- -------- ---------- ----------

### Relative Variations in Noise Figure and Required CNR

Figure 5-6 shows the required CNR for each receiver as a function of
noise figure on each of the three tested channels. Contour lines can be
used to read the combined effect of the two parameters on minimum signal
at TOV. It is clear from the plot that most of the variation in receive
sensitivity (i.e., minimum signal level at TOV) of the DTV receivers is
due to variations in receiver noise figures rather than variations in
the CNR required by the demodulator. In fact, based on standard
deviations of the parameters, variability in noise figure among the
receivers is 4.2 times as high as the variability in required CNR on
channel 30, where the noise figure variations are smallest. On channels
10 and 3, respectively, the noise figure shows 7 and 16 times the
variability of required CNR.

![](media/image8.wmf){width="2.410416666666667in"
height="3.803472222222222in"}
![](media/image9.wmf){width="2.0284722222222222in"
height="3.797222222222222in"}

\(a\) Required CNR (b) Minimum Signal at TOV

[]{#__RefHeading___Toc118693142 .anchor}Figure 5‑8. Relationship between
Minimum Signal at TOV and Required CNR

![](media/image10.wmf){width="6.497916666666667in"
height="4.293055555555555in"}

[]{#__RefHeading___Toc118693143 .anchor}Figure 5‑9. Noise Figure on
Three Channels

![](media/image11.wmf){width="6.497916666666667in"
height="4.2868055555555555in"}

[]{#__RefHeading___Toc118693144 .anchor}Figure 5‑10. Noise Figure on
Channel 3 (Low VHF)

![](media/image12.wmf){width="6.497916666666667in"
height="4.2347222222222225in"}

[]{#__RefHeading___Toc118693145 .anchor}Figure 5‑11. Noise Figure on
Channel 10 (High VHF)

![](media/image13.wmf){width="6.497916666666667in"
height="4.228472222222222in"}

[]{#__RefHeading___Toc118693146 .anchor}Figure 5‑12. Noise Figure on
Channel 30 (UHF)

![](media/image14.wmf){width="6.497916666666667in"
height="4.2347222222222225in"}

[]{#__RefHeading___Toc118693147 .anchor}Figure 5‑13. Required CNR Versus
Noise Figure

#  PERFORMANCE AGAINST MULTIPATH USING FIELD CAPTURES

Chapters 3 through 5 dealt with over-the-air reception performance of
the DTV receivers with a signal that is [un]{.underline}impaired by
multipath. Chapter 6 addresses the issue of multipath by determining the
ability of each receiver to process broadcast DTV signals that were
received and recorded on actual television antennas at various locations
in New York City and Washington, DC.

The selected digital RF recordings, also called "captures" or "field
ensembles", were 47 of the 50 captures recommended by the ATSC for DTV
receiver testing.[^20] ATSC's characterization of the 50 captures is
worth noting.

> *"Most of the field ensembles contain data captured at sites where
> reception was difficult. The field ensembles are clearly not meant to
> represent the statistics of overall reception conditions but rather to
> serve as examples of difficulties that are commonly experienced in the
> field."*[^21]

Three of the 50-recommended captures were excluded from testing with the
consumer DTV receivers because they contain no video content and
therefore require specially instrumented receivers for testing; however,
extrapolation of instrumented receiver test results for those three
captures to the consumer receivers is discussed later in this chapter.
The remaining 47 captures break down as follows:

1.  sites characterized as urban (19), suburban (12), rural (2), and
    various other categories that overlap these designations (14);

2.  single-family homes (18), townhouses (8), and apartments (21);

3.  indoor antennas (39) and outdoor log-periodic antennas (8)

Each of the captures was recorded in the year 2000 by the Advanced
Television Test Center (ATTC) or the Association for Maximum Service
Television (MSTV) using specialized digital capture equipment. Each
capture has duration of either 23 or 25 seconds. An RF player allows the
recorded signal to be translated to any standard TV broadcast channel
and played back as a repeating loop.

Appendix B lists the captures and summarizes some of the test results.

## Measurement Method

The test configuration was essentially the same as that described in
Chapter 3, for the white-noise threshold measurements, except that no
noise was injected. The nine-way splitter allowed the signal to be
simultaneously applied to as many as eight DTV receivers and a vector
signal analyzer. All 47 selected RF captures were played through each
group of receivers. Performance is reported in this chapter as the
number of captures successfully played by a receiver for two different
criteria of success. As a consistency check, receiver D3 was included in
each group of eight receivers that were tested; the numbers of captures
played successfully on receiver D3 on the various tests were consistent
within one count.

Signal attenuators were adjusted to provide a nominal input of -30 dBm
at the receiver antenna ports. The attenuator was not separately
adjusted for each capture file; consequently, the actual injected level
within the channel bandwidth of 6 MHz.varied from -38 to -28 dBm based
on the level recorded in each capture. All but four of the captures
played at an in-channel level within 2 dB of the nominal.

Successful playback of a capture was defined in terms of the number of
video error bursts observed during a single playback loop after the loop
had played at least three times. (In many cases the performance was
monitored over several loops and, if the results varied, a median value
was chosen.) A video error burst lasting more than one second was
counted based on the approximate duration in seconds. Thus, an error
burst lasting three seconds was counted as three errors. Errors
occurring during or immediately after the loop-restart time were not
counted, nor were errors associated with known defects (dropped symbols)
in eight of the captures, as documented by the ATSC.[^22]

The testing was performed on channel 30. It should be noted that with
many of the DTV receivers, simply tuning to channel 30 was not
sufficient to ensure successful acquisition of the TV signal---even with
one of the easier captures. The original source material for the
captures was recorded from eight different DTV broadcast stations in two
cities. Because of the facts that multiple programs can be broadcast on
a single channel and that most DTV channels are associated with an
equivalent analog channel number that is used in selecting the station
(PSIP requirements),[^23] many of the receivers were "confused" by
changing broadcast stations from playback of one capture to playback of
the next, even though the RF channel remained constant. As a result,
various methods such as rescanning the channels were necessary to get
many of the receivers to operate after changing between captures that
originated on different TV channels. To save time in the process, the
captures were sorted by originating broadcast station before testing,
and were further sorted to allow the more benign captures from a given
broadcast station to be played first, in order to lock the receivers
onto each new broadcast station.

Further details on the measurement procedure are contained in Appendix
A.

## Results

Figure 6-1 shows the results of testing each DTV receiver with each of
the 47 RF captures. The general format of the plot is as described in
Chapter 3 in the section titled, "Format of the Bar Graph Data", but
with a few differences. The blue (lower) portion of each bar represents
the number of captures that played without a visible error during a
single loop of the capture. The upper portion of each bar adds the
captures that played with no more than two visible errors during a
single loop of capture.

It should be noted that, unlike the plots presented in earlier chapters
of this report, increased performance in this plot is represented by
taller bars. Also, in addition to the four category groupings of DTV
receivers, Figure 6‑1 includes an additional bar on the right, labeled
2000REF. This receiver was retained from field testing in the year 2000
and was included in the RF capture testing presented here. Further
discussion of this receiver is provided later in this chapter as well as
in Chapter 7.

### Nominal Performance and Variation Among Samples

Unlike the results of other testing presented in this report, the
results of testing against the RF captures are heavily clustered into
two major performance tiers. The upper-tier (better) performers
successfully played about 29 captures without error and about 37
captures with two or fewer errors. The lower-tier performers
successfully played about 7 captures without error and about 9 with two
or fewer errors. Neglecting receivers D1 and L2, all results fall within
±2 captures of one of these nominal results, as shown in Table 6‑1.
Receivers D1 and, perhaps, L2, appear to represent an additional
performance tier slightly above the lower tier; this tier will be
designated as "lower tier+".[^24]

The upper-tier performers represent a quantum leap in ability to handle
the most difficult multipath conditions. The receivers that tested in
this tier are known to include the latest generation of demodulator
chips from at least two of the major DTV chip developers.

[]{#__RefHeading___Toc118693189 .anchor}Table 6‑12. Number of Captures
Successfully Played By Each Performance Tier

  ------------- ----------- -------------------- -------------------------
                Number of   Number of Captures   Number of Captures Played
                Consumer    Played with No       with No More Than 2
                Receivers   Errors               Errors

  Lower Tier    16          7 ±2                 9 +2/-1

  Lower Tier+   2           8 and 12             14 and 16

  Upper Tier    10          29 ±2                37 ±2
  ------------- ----------- -------------------- -------------------------

It should be noted that some of the RF captures may contain recording
flaws---other than the dropped symbols discussed earlier---that could
prevent error-free demodulation regardless of how advanced the
demodulator technology may be. For example, four of the captures for
which no tested receiver achieved demodulation free of visual errors
were identified by the ATSC as having possible non-linearities caused by
high-level adjacent channels overdriving the recording system. These or
other potential flaws may preclude a 100% success rate on the 47
captures from ever being achieved by any demodulator; consequently, we
view the multipath-performance data based on these captures to be useful
for purposes of comparing receivers, but not as an absolute measure of
performance.

### Extrapolation to the Three Captures Lacking Video Content

Three of the ATSC-recommended RF captures lacked video content and could
not, therefore, be tested with the consumer DTV receivers; however, they
were tested with a five-year-old instrumented DTV receiver, labeled
"2000REF" in Figure 6‑1. That receiver provides visual and audible
indications when segment errors[^25] occur during demodulation of the
DTV signal.

Tests were performed first using three captures [with]{.underline} video
content (labeled as numbers 27, 29, and 45 in Appendix B). These
captures exhibited 4, 1, and 2 visual errors, respectively, with the
2000REF receiver. Results showed a one-to-one correspondence of segment
error bursts with observed video error bursts for these captures.[^26]

Tests of the 2000REF receiver with the captures having no video content
(labeled 22, 24, and 44 in Appendix B) showed no segment errors. The
absence of segment errors indicates that the 2000REF receiver would have
exhibited no visible errors on these captures had there been video
content to observe. Given that this five-year-old receiver---now
obsolete by two demodulator generations---is among the worst performing
of the tested receivers in terms of multipath performance (per
Figure 6‑1), it is considered likely that all of the tested consumer
receivers would have exhibited no visual errors for these three captures
had there been video content to observe. Consequently, if one wanted to
extrapolate performance against the entire set of 50 ATSC-recommended RF
captures from the tests of the 47 with video content, it is likely that
three zero-error successes should be added to the results for each
receiver.

### Variation With Product Type and Price

Interestingly, both upper-tier and lower-tier performers appear in all
three price categories of DTVs. This suggests that performance is not a
function of price---at least in the DTV category.

On the other hand, none of the set-top boxes---the least expensive way
to receive a digital broadcast if you connect it to an existing
television---perform at the upper tier level.

Some understanding of these results can be achieved by looking at the
introduction date of each tested receiver to the U.S. market.
Introduction dates (by month and year) for 25 of the 28 receivers tested
for this report were provided by the manufacturers; the remaining three
were determined by a web search. Though introduction dates are not
reported here in order to avoid possible date-based linking of
individual product models with the receiver designations used in this
report, the following observations are relevant.

1.  All ten upper-tier performers were introduced in or
    [after]{.underline} March, 2005.

2.  The set-top boxes---all of which performed at the lower tier or
    "lower tier+"---were introduced in or [before]{.underline} November,
    2004.

3.  Of the lower-tier or lower-tier+ integrated DTVs (i.e., excluding
    set-top boxes), two were released in the latter part of 2004 and the
    remaining eleven were introduced between March and July, 2005.

Since the set-top box models available on the market at the time of the
reported tests were 2004 or earlier models,[^27] their lower-tier or
"lower-tier+" performance reflects the lack of availability of the newer
generation of DTV demodulator chips at the time of product design.

Among the DTVs, it is clear that introduction dates in or after March
2005 are consistent with feasibility of including of the newer
technology. Among the tested DTVs that were introduced in or after March
2005, 48 percent performed at the upper tier level. It is probable that
some of the products introduced in this time frame carried over
tuner/demodulator designs from a previous generation.

One would expect that, as future models are released, the newer
generation demodulator technology will migrate to an increasing extent
into all DTV product categories, including set-top boxes, and that, at
some point in the near future, the improved technology will be contained
in all newly introduced receivers. In the meantime, there is little
publicly available information to assist those consumers who live in
locations characterized by challenging multipath conditions in selecting
DTV receivers that achieve the upper tier of performance.

### Relationship Between Multipath Performance and White Noise Threshold

There is some reason to expect that improvements in multipath
performance---which is achieved in part by increasing the number of taps
in the demodulator's equalizer circuit---might come at the expense of
poorer white noise threshold, because, even in the absence of multipath,
the additional taps could be expected to add noise that is related to
carrier amplitude. (Since an automatic gain control would be expected to
provide sufficient gain to amplify the input signal---whatever its
level---to a fixed level for processing by the demodulator, one would
expect that the tap noise generated after this variable amplification
would be at a fixed level relative to the DTV signal rather than at a
fixed level relative to the antenna input---hence the impact would
appear as a degradation to required CNR \[white noise threshold\] rather
than an increase in noise figure.)

Figure 6-2, shows the measurements of white noise threshold (from
Chapter 3) plotted against multipath performance as measured by the
number of RF captures (out of 47) that were successfully played without
error. The lower tier of multipath performers (presumably containing
earlier generation 8‑VSB decoders) had a median CNR threshold of 15.3
dB,[^28] which is slightly worse than the 15.19 dB threshold achieved by
the ACATS Grand Alliance prototype receiver.[^29] Until the most recent
VSB decoder generation came to market, the trend of the earlier VSB
decoder improvements was a very slight worsening of the CNR at threshold
as a tradeoff for improved multipath performance. The 15.1 dB median CNR
threshold for the upper tier of multipath performers suggests that this
trend is over. In fact, the seven best-performing receivers in terms of
white noise threshold are in the upper tier of multipath performance.

![](media/image15.wmf){width="6.497916666666667in"
height="4.247916666666667in"}

[]{#__RefHeading___Toc118693148 .anchor}Figure 6‑14. Performance Against
47 RF Captures

![](media/image16.wmf){width="6.497916666666667in"
height="4.209027777777778in"}

[]{#__RefHeading___Toc118693149 .anchor}Figure 6‑15. White Noise
Threshold Versus Multipath Performance

#  INFERRED PERFORMANCE AGAINST REPRESENTATIVE MULTIPATH CONDITIONS

The measurements presented in the previous chapter show that DTV
receivers on the market at the time of these tests differ markedly in
their ability to handle certain difficult multipath conditions. In order
to understand the impact of these differences, one would also like to
know how prevalent are the types of multipath conditions that
differentiate receiver performance. If those conditions occur only
rarely, then the performance differences will not be of consequence to
most consumers; on the other hand, if they occur frequently, then the
performance differences between "upper tier" and "lower tier" performers
will radically affect many consumers.

Although an investigation of the frequency of occurrence of various
multipath conditions is beyond the scope of this report, some of the
measured data presented in Chapter 6 can be combined with results from a
year-2000 FCC field investigation to provide at least a partial answer.

## Multipath Capability Based on Year-2000 Field Tests

In 2001, the FCC Laboratory reported the results of year-2000 field
tests of DTV coverage in Washington, DC and of DTV receiver
performance.[^30] In that study, the performance of six DTV receivers
was evaluated at 60 locations for reception of two broadcast UHF DTV
stations (channels 34 and 48). Nine of the locations were specifically
selected for high-multipath conditions; however, 51 locations---referred
to as "coverage sites", were selected in ways that can be expected to
yield more representative results. It is these 51 sites that are of
interest for the current analysis.

Of the 51 coverage sites, 38 were located at five-mile intervals along
radials from the broadcast antenna of digital channel 48 in Washington,
DC. The other 13 coverage sites were chosen from sites randomly selected
from within a box 17.5 miles on a side, centered on the same broadcast
antenna.[^31]

At each site, reception performance measurements were made using at
least two antenna systems:

1.  a log-periodic, outdoor-type antenna on a 30-ft. mast, and

2.  one of two indoor-type antennas on a 7-ft. tripod located outdoors.

The tripod-mounted antenna measurements were intended to indicate
reception performance that could be expected with an antenna located
indoors to the extent that could easily be determined given that access
to homes or other buildings at randomly selected sites is not generally
available. Though the antenna was not located indoors, the height and
antenna type were consistent with indoor use. In general, a bow tie
antenna was used as the "indoor-type" antenna. If the bow tie failed to
achieve reception, a small, indoor, UHF log-periodic antenna ("Silver
Sensor") was tried.

The tests included six DTV receivers, one of which was an instrumented
prototype receiver to be used as a reference. Initially, the reference
receiver was a [second]{.underline}-generation Zenith ProDemodulator.
After two thirds of the testing was complete (on July 17, 2000), that
receiver was replaced with a [third]{.underline}-generation Zenith
ProDemodulator. The third generation included an equalizer with longer
ghost cancellation times and slightly improved pre-ghost performance at
the expense of slightly degraded white noise performance, relative to
the second generation.

That same third-generation receiver was tested this year, along with the
28 current-generation consumer receivers, to determine performance
against the 47 RF captures, as described in Chapter 6. The result for
the third generation reference receiver is shown as the right-most bar
(labeled "2000REF") of Figure 6-1. In the current tests, that
receiver---with equalizer technology now two generations behind the
latest technology---tied for either the worst or second worst
performance (depending on whether counting the zero-error data or the
two-error data) when included with the current crop of receivers that
were tested. Given that the third generation was used for only one third
of the year-2000 tests and that a second generation receiver---with
inferior equalizer technology---was used for two thirds of those tests,
one can assume that the reported field test results for the "reference
receiver" from those earlier tests correspond to receiver with multipath
performance at or below the level shown by the "2000REF" bar in
Figure 6‑1.

In the year-2000 tests, all but one of the 51 sites exhibited field
strengths judged to be large enough for theoretical DTV reception.[^32]
Using the mast-mounted, outdoor-type antenna, the reference receiver
received channel 34 with no visible picture errors in all 50 of those
sites and received channel 48 without visible errors in 49 of the 50
sites. Thus, the reference receiver successfully handled multipath
conditions in 99 percent of the test-site/broadcast-station combinations
with the mast-mounted antenna. When using the tripod-mounted indoor-type
antennas (including the Silver Sensor, when needed), the reference
receiver handled 85 percent of the test-site/broadcast-station
combinations without visible picture errors.

Thus, receivers performing at or below the level of the 2000REF receiver
shown in Figure 6‑1 were able to successfully handle 99 percent of the
multipath situations in the "coverage tests" when using a mast-mounted
outdoor antenna. Though the tests involved only one metropolitan area
and the sample size was too small to consider these numbers
statistically accurate, the sites selected are expected to be far more
representative of randomly selected real world conditions than the
ATSC-recommended sites, which were chosen because of their difficult
multipath conditions. Given that the 2000REF results show performance at
or below almost all of the lower-tier performers in the Figure 6-1, one
can reasonably assume that, even lower-tier multipath performance (as
defined in Chapter 6) is adequate to handle the vast majority of
reception conditions (at least in the Washington, DC area) when the
receiver is paired with a good outdoor, mast-mounted antenna.

Similarly, receivers performing at or below the level of the 2000REF
receiver shown in Figure 6‑1 were able to successfully handle 85 percent
of the multipath situations in the "coverage tests" when using a
indoor-type antenna at a 7-foot height (but located outdoors). It
appears likely, then, that multipath performance at the lower tier of
Figure 6-1 may be adequate for most locations in conjunction with an
indoor antenna, but that improved multipath performance (e.g., the upper
tier of Figure 6‑1) might offer benefits in many locations.

## Impact of Representative Multipath on Required CNR

The year-2000 field tests also offer some insight into the impact of
multipath on required CNR for a receiver.

Those tests included measurements of required CNR at each site. The
required CNR was determined by adding white Gaussian noise to an
amplified version of the signal received from the antenna and adjusting
the noise level until the threshold of visibility (TOV) was observed.

Though the precision of the measurements was limited by the use of
one-dB steps in adjusting the noise level, the median required CNR
across all of the coverage sites provides an indication of the required
CNR in real world multipath conditions. In general it was found that the
newer generation receivers performed better---i.e., had a lower required
CNR---that older generation receivers. When used with the mast-mounted
antenna, the newest generation receiver that was used throughout the
test period for the 2001 report (a "third generation" receiver
identified as receiver 5 in that report) exhibited a median required CNR
of 15.9 dB across all "coverage sites" tested for one of the received
broadcast stations and 16.0 dB for the other. With the tripod-mounted
antennas, the corresponding numbers were 17.0 and 16.6 dB.

Absent better information, a required CNR of 16.0 dB may be a reasonable
estimate of reception performance in typical multipath conditions if an
outdoor antenna is used.

#  SUMMARY AND CONCLUSIONS

The laboratory-based measurements performed for this report emulated two
types of over-the-air reception conditions for DTV receivers:

> \(1\) Unimpaired signal (i.e., no multipath) \[Chapters 3 -- 5\], and
>
> \(2\) Signal impaired by multipath (ghosts) \[Chapter 6\]---focussing
> on particularly difficult multipath conditions.

The unimpaired signal measurements can be used to quantitatively predict
receiver performance under benign reception conditions---i.e., with
little multipath. The multipath tests provide a basis for comparing the
ability of different DTV receivers to handle difficult multipath
conditions---without directly addressing the frequency of occurrence of
those multipath conditions.

The linkage developed in Chapter 7 between the new, laboratory-based
measurements performed for this report and earlier FCC field-test data
provides a basis for anchoring the multipath results to representative,
real-world reception conditions.

The purpose of this report has been to provide an empirical basis for
answering three questions that derive from study requirements imposed by
Congress as part of SHVERA \[Chapter 1\]. Those questions are as
follows.

> \(1\) Is there is a wide variation in the ability of reasonably-priced
> consumer digital television sets to receive over-the-air signals, such
> that at a given signal strength some may be able to display
> high-quality pictures while others cannot?
>
> \(2\) Is such variation related to the price of the television set?
>
> \(3\) Should such variation be factored into setting a standard for
> determining whether a household is unserved by an adequate digital
> signal?

In addressing these questions, separate answers will be provided for
benign signal conditions (little multipath) and difficult multipath
conditions. The third question will be addressed by comparing measured
results to the receiver performance planning factors in OET-69.

The benign signal case will be evaluated in terms of the measured values
of minimum signal at the threshold of visibility of errors (TOV) for the
receivers. This specifies the ability of a DTV receiver to operate with
a weak signal---absent significant multipath or interference. To provide
a better understanding of differences among receivers, the discussion
will also delve into two receiver parameters that combine to determine
the minimum signal at TOV. These are:

1.  the white noise threshold (required carrier-to-noise ratio \[CNR\]);
    and

2.  the effective noise figure of the receiver.

The first of these characteristics is a demodulator characteristic that
is independent of which TV channel contains the signal of interest. The
second is a measure of the internally generated electronic noise of the
receiver; it [does]{.underline} vary with TV channel. In reporting
channel-dependent data, results are presented for the low-VHF, high-VHF,
and UHF bands, which were represented in the measurements by TV channels
3, 10, and 30.

## Variation in Reception Performance

### For Benign Signal Conditions

In the low-VHF band, the variation in reception performance among the
tested DTV receivers was moderately high. The minimum signal level at
TOV exhibited a 3.7‑dB standard deviation among the receivers. 89
percent of the receivers exhibited performance within 5.1 dB of the
median performance, but two (seven percent) same-brand receivers were
significantly worse than the median---by 10.6 and 12.5 dB. Omitting
those two receivers from the data set would reduce the standard
deviation to 2.3 dB.

In the high-VHF and the UHF bands, the variation in reception
performance among the tested receivers was small. In the high-VHF band,
the minimum signal level at TOV exhibited a 1.6‑dB standard deviation;
89 percent of the receivers exhibited performance within 3.1 dB of the
median, and the poorest performing receiver exhibited a performance
level 4.3 dB worse than the median. In the UHF band, the minimum signal
level at TOV exhibited a 0.9‑dB standard deviation; 89 percent of the
receivers exhibited performance no worse than 1.3 dB poorer than the
median, and the poorest performing receiver exhibited a performance
level 2.5 dB worse than the median.

Most of the variation in reception performance among the tested
receivers was due to differences in receiver noise figure rather than in
required CNR. The noise figure variations were larger than the
required-CNR variations by factors ranging from 4.2, in the UHF band, to
16, in the low-VHF band.

### For Difficult Multipath Conditions

Independent of band, there was a wide variation in ability of the
receivers to handle difficult multipath conditions; however, linkage of
the current results with earlier field test results suggest that the
observed performance differences are of no consequence in the vast
majority of reception locations, if an outdoor, mast-mounted antenna is
used. When an indoor antenna is used, the linkage suggests that the
observed performance differences would be significant in many, but
probably not most, locations.

In tests against RF captures recorded from antennas at sites
specifically selected for their challenging multipath conditions, the
multipath-handling capability of the receivers fell primarily into two
tiers of performance. The upper (better-performing) tier included ten
receivers. The lower tier included 16 receivers. Two receivers fell in
between the two tiers, but closer to the lower tier. The upper-tier
receivers were able to handle about four times as many of the RF
captures as the lower tier.

The FCC's year-2000 field tests at 51 sites that were selected without
regard to multipath---and thus more likely to be representative of the
typical range of common reception conditions than the RF captures---can
be used to put the current multipath test results in perspective. A
now-obsolete instrumented receiver left over from those earlier field
tests was retested this year against the RF captures and was found to
perform at the bottom of the lower performance tier. But, in the year
2000 field tests that now-inferior receiver successfully handled
multipath in 99% of the combinations of site and broadcast station,[^33]
when a mast-mounted outdoor antenna was used. The success rate dropped
to 85 percent when an indoor-type antenna was used,[^34] indicating an
increased likelihood that better multipath performance in the receiver
would have helped.

## Price-Dependence of Reception Performance

### For Benign Multipath Conditions

In assessing the price-dependence of receiver performance, one must
consider two things:

\(1\) whether an observed variation of performance with price among the
tested receivers is statistically significant---i.e., whether it
represents a real trend among DTV receivers currently on the market or
whether it is a statistical artifact of the particular selection of
receivers that were tested; and,

\(2\) whether an observed variation of performance with price is of
sufficient magnitude to significantly affect television performance.

In the low-VHF band, though the variability in performance among the
receivers was moderately high, the variability among the price
categories was small, and no statistically significant price-dependence
of that variation was found. In fact, the median performance of the
low-cost TVs was slightly better than that of either the mid-priced or
high-priced TVs. The median performance of the tested set-top boxes was
poorer than that of the integrated DTVs by 2.3 dB, though it must be
noted that these were older designs (2004 and earlier models that were
still on the market at the time of this report) than the DTVs.

In the high-VHF and the UHF bands, the variation in reception
performance with price was judged to be both small and not statistically
significant. The median performance of the high-cost TVs differed from
that of the low-cost TVs by less that 0.2 dB. Set top boxes exhibited
median performance 0.6 dB and 0.7 dB worse than the median of all TVs in
the low-VHF and UHF bands, respectively.

### For Difficult Multipath Conditions

The tested receivers fell into two distinct tiers of multipath-handling
capability---the upper tier representing a significant performance
improvement associated with at least two companies' newest generation of
demodulator chips.

Given that both tiers of performance appeared in all three price ranges
of DTV receivers, there appears to be no inherent price dependence among
the DTVs; however, there was a complete absence of upper-tier performers
among the tested set-top boxes. This absence is attributed to the older
designs of the set-top box products---all of which were introduced in
the year 2004 or earlier. Among the tested receivers, none that were
introduced before March 2005 were found to exhibit upper-tier
performance, whereas 48 percent of those introduced in or after that
month performed at the upper tier level.

## Reception Performance Relative to OET-69

### For Benign Multipath Conditions

The results show no clear need to adjust planning factors in OET-69 for
application to SHVERA. Table 8‑1 shows that, for benign multipath
conditions, the poorest performing receiver category---*set-top
boxes*---exhibited median performance (as indicated by minimum signal at
TOV) closely matching predictions based on current OET-69 planning
factors, with median performance exceeding the OET-69 predictions by 1.7
dB in high VHF and falling below OET-69 performance levels by less than
1 dB in low VHF and UHF. The median low-cost DTV performance matched
OET-69 in the UHF band and was better than OET-69 by about 2 dB in the
VHF bands. It should be noted that the tolerance on these measurements
is about ±1 dB.

\[It is also noted that, in terms of minimum signal at TOV, the overall
median performance of the tested receivers (-82.2, -83.2, and -83.9 dBm,
in low VHF, high VHF, and UHF, respectively) matches, within measurement
accuracy, the minimum performance standard of -83 dBm recommended by the
ATSC.[^35]\]

[]{#__RefHeading___Toc118693190 .anchor}Table 8‑13. Net Performance for
Unimpaired Signal Relative to OET-69 Model

  --------------- ----------------- ------------------- ------------------
  **Band**        **Median of All   **Median Low-Cost   **Median Set-Top
                  Test Samples**    DTV**               Box**

  **Low VHF       1.2 dB better     2.3 dB better       0.7 dB worse
  (Ch.3)**                                              

  **High VHF      2.2 dB better     2.4 dB better       1.7 dB better
  (Ch.10)**                                             

  **UHF (Ch.30)** 0.1 dB worse      0.1 dB better       0.8 dB worse
  --------------- ----------------- ------------------- ------------------

A breakdown of the results by individual planning factors is shown in
Table 8-2. Median required carrier-to-noise ratios (CNRs) closely match
the OET-69 value, as does the system noise figure in UHF. The median VHF
noise figures of the tested receivers were better than the OET‑69
values, with the exception of the set-top box median in low VHF, which
was only 0.5 dB above (worse than) the OET‑69 value.

[]{#__RefHeading___Toc118693191 .anchor}Table 8‑14. Planning Factor
Measurements with Unimpaired Signal

  ----------------------- ------------ -------------- ----------- -----------
  **Planning Factor**     **OET-69**   **Overall      **Median\   **Median\
                                       Median of Test Low-Cost    Set-Top
                                       Samples**      DTV**       Box**

  **Required              15.2[^36]    15.3           15.3        15.4
  Carrier-to-Noise Ratio                                          
  (dB)**                                                          

  **System Noise Figure   10.0         8.8            7.4         10.5
  (dB) in Low VHF**                                               

  **System Noise Figure   10.0         7.6            7.5         7.8
  (dB) in High VHF**                                              

  **System Noise Figure   7.0          6.9            6.9         7.5
  (dB) in UHF**                                                   
  ----------------------- ------------ -------------- ----------- -----------

Note: for all parameters, lower values correspond to better performance

### Adjustment for Multipath

The required CNRs presented above were measured for an unimpaired
signal. In the presence of significant multipath, it is known that
higher CNRs are required. We have performed no measurements of this
effect on the current generation of receivers; however, field tests from
the year 2000 yielded a value of 16 dB for the median required CNR
across 50 test sites using the then newest generation of DTV receiver
hardware and an outdoor, mast-mounted antenna. This is only 0.7 dB above
the median measured value from the receiver tests using a benign signal.
If the net performance data of Table 8‑1 were degraded by 0.7 dB to
reflect this value for required CNR, it can be seen that the results
would still closely match OET-69 predictions.

### Overall Conclusion Regarding Adjustment to Planning Factors 

While adjustments to the OET-69 planning factors could be made based on
the test results presented in this report in combination with results
from the year-2000 field tests, the overall effect on performance
predictions would be small. Combining the 16-dB required CNR value, as
discussed above, with the overall median noise figures would yield more
optimistic predictions that the current OET-69 by 0.4 dB and 1.6 dB,
respectively, in the low-VHF and high VHF bands, and less optimistic
predictions by 0.7 dB in the UHF band. Given the tolerances on the
measurements, such adjustments to the existing methodology are not
recommended.

#######  TEST CONFIGURATIONS, ISSUES, AND PROCEDURES

## Test Configurations

This appendix provides additional information regarding test
configurations, procedures, and issues that arose during the testing.

### General Information on the Test Configurations

All test and measurement setups maintained a 50-ohm impedance
throughout, except at the signal source and the consumer TV inputs,
which were each specified to be nominally 75 ohms. (An older,
instrumented reference receiver identified as 2000REF in this report had
a 50 ohm input impedance.) The 75‑ohm devices were matched to the rest
of the test setup through minimum-loss impedance-matching pads, except
that, in the test setup that employed a splitter, an impedance-matching
transformer was used at the signal source to reduce losses.

Attenuation pads were used throughout each test configuration to reduce
the effects of any impedance mismatches at places where such mismatches
were considered likely or would be expected to have a significant
impact. A 50-to-75-ohm impedance-matching pad used at the input of each
consumer DTV receiver served both as an impedance-matching device and as
a 5.8-dB attenuator to attenuate reflections due to deviations of the TV
antenna inputs from the nominal 75-ohm value.[^37]

### Splitter Test Configuration

Figure A-1 shows a block diagram of the "splitter test configuration",
which was used for tests of white noise threshold and multipath
performance.

An RF player (Sencore RFP-910) playing the "Hawaii_ReferenceA" file
supplied with the player was used as the ATSC 8-VSB signal source, for
reasons discussed in the "Test Issues" section of this appendix.
Amplifiers for the signal operated at RMS levels that were more than
17-dB below the specified 1-dB compression points in order to ensure
linearity.

For the white noise tests, noise was supplied by a noise generator,
which was then externally filtered to roll off the noise beyond 700
MHz---well above the tested frequencies.

Both signal and noise levels were adjusted using step attenuators that
could provide 0 to 81 dB of attenuation in 0.1‑dB steps.

Signal and noise were combined using a directional coupler, then divided
nine ways by means of two cascaded layers of three-way splitters, each
specified to have a minimum isolation of 14 dB between inputs. The
splitters were followed by 25-foot long, well-shielded, low-loss cables,
each of which drove either an impedance-matching pad (nominally 5.8‑dB
power attenuation) for connection to a consumer TV receiver or a 50-ohm
attenuator pad (nominally 6‑dB attenuation) for connection to measuring
instruments or to the instrumented receiver. The nine outputs---at the
output of the final pads---are designated by port numbers Pt1, ... Pt9
when the final pad is an impedance-matching pad, as when driving a
consumer DTV. An "a" is suffixed onto the port numbers when the final
pad is a 50-ohm pad, as when driving a measurement instrument (vector
signal analyzer or spectrum analyzer) or an instrumented receiver having
a 50-ohm input impedance. Port Pt5a was always used as the measurement
port.

The splitter arrangement allowed the signal and noise to be
simultaneously delivered to as many as eight TVs and to a vector signal
analyzer used for measurements. Any amplitude mismatch between the
various ports, though small, was not of concern because the signal
levels for multipath testing were not critical and because white noise
threshold tests involve the ratio of two measurements (signal and noise)
that were made on the same port and using the same amplitude range of
the spectrum analyzer to eliminate the effect of small errors in
absolute measured levels.

### Minimum Signal Test Configuration

Figure A-2 is a block diagram of the configuration used for measuring
minimum signal at TOV.

An RF player (Sencore RFP-910) playing the "Hawaii_ReferenceA" file
supplied with the player was used as the ATSC 8-VSB signal source, for
reasons discussed in the "Test Issues" section of this appendix.

Because minimum input signal at TOV is an absolute measurement rather
than a ratio, a signal splitter was not used for these tests. The
25-foot low-loss coaxial cable carrying the signal was connected through
a 10 dB attenuator and an impedance matching pad (50 to 75 ohms, 5.8 dB
power attenuation) to the TV input. After signal level was adjusted to
achieve TOV on the TV, the cable and 10-dB pad---but not the impedance
matching pad---were moved to the vector signal analyzer input for the
signal level measurement, which then had to be corrected for measured
loss of the impedance matching pad.

## Calibration and Signal Quality Tests on Test Setups

### Impedance-Matching Devices

The power loss of 14 identical minimum-loss impedance-matching pads
(Trilithic model ZM-57) and two impedance-matching transformers
(Trilithic ZMT-57) were measured as a function of frequency. The devices
were labeled with individual numbers for identification; designations
were MLP#1 through MLP#14 for the minimum-loss impedance-matching pads
and TT#1 and TT#2 for the transformers.

The losses of the individual impedance matching devices were determined
from loss measurements performed on back-to-back pairs of
impedance-matching devices. These measurements were performed by
measuring signal levels versus frequency for a tracking generator signal
and for that signal as attenuated by a back-to-back pair of
impedance-matching devices (50 ohms to 75 ohms to 50 ohms) to determine
the loss versus frequency for each tested pair of devices. (Loss was
computed by subtracting the measured output level versus frequency of
the tested devices from the output level versus frequency of the
tracking generator, measured with the same spectrum analyzer settings
\[including input attenuation and reference level\] in order to ensure
that loss measurements were accurate.) The measured combinations
included MLP#13 with each of the other devices and MLP#14 with each of
the other devices. The difference between losses of MLP#13 and MLP#14
was computed as the difference between average loss of the combinations
of MLP#13 with MLP#1 through MLP#12 and average loss of the combinations
of MLP#14 with MLP#1 through MLP#12. The loss of MLP#13 combined with
MLP#14 determined the sum of losses of MLP#13 and MLP#14. Combining this
information allowed computation of the individual losses of MLP#13 and
MLP#14. The loss of each of the other devices could then be computed by
subtracting the loss of MLP#13 from the measured loss of the combination
of that device with MLP#13, or by performing a similar calculation based
on MLP#14; in fact, both computations were performed and the results
averaged to determine the loss of those devices.

The unit-to-unit variation of the loss of the impedance matching pads at
channel-30 frequencies was of interest because of their use in the
splitter test setup. The pads were found to be quite well matched---with
samples ranging from 5.79 to 5.84 dB at the frequency of TV channel 30.

All of the pads and both transformers were found to be flat to within
0.02 dB across the 6‑MHz bandwidths of each tested channel (3, 10, and
30).

TV-channel-specific measurements of absolute loss of one impedance
matching pad (MLP#12) were used in determining minimum signal at TOV
because the actual signal level measurement did not include the loss of
that pad. Those losses were 5.70, 5.73, and 5.82 dB, respectively, on
channels 3, 10, and 30.

The frequency-dependent measurements of the loss of one
impedance-matching transformer (TT#1) were used in determining the
frequency response of the splitter test configuration to the 50-ohm
outputs (Pt5a and Pt8a).

### Splitter Test Configuration

Because of the complexity of the splitter test configuration, which
included amplifiers, a noise generator, a directional coupler, and
splitters that were not a part of the simpler minimum-signal test
configuration, additional tests were performed to verify its
performance. The tests evaluated the frequency response (including the
potential effect of errors in input impedance of the TVs), port-to-port
matching, signal and noise spectral characteristics, and signal quality.

#### Frequency Response and Effect of Mismatched Loads {#frequency-response-and-effect-of-mismatched-loads .unnumbered}

The splitter test configuration (Figure A-1) provided nine identical
output ports, each of which could be configured for connection to a
75-ohm device (the antenna port of a consumer DTV) or to a 50-ohm device
(vector signal analyzer, spectrum analyzer, or an instrumented reference
receiver having 50 ohms input impedance). Configuration of each port was
performed by connection of either an impedance-matching pad (50 to 75
ohms, 5.8 dB nominal power attenuation) or a 50-ohm pad (6 dB ±0.5 dB)
at the final output of the port (end of the 25-foot low loss cable). The
ports were designated Pt1, ... Pt9 when matched to 75 ohms. A suffix "a"
was added to the designation of ports matched to 50 ohms. Only two ports
were ever configured for 50 ohms during the reported tests: the fifth
port (Pt 5a), which always served as the measurement port; and the eight
port (designated Pt8a, when so configured), which was used to connect to
the instrumented, 50-ohm input receiver designated 2000REF for one set
of tests.

Figure A-3 shows the frequency response of the entire test setup from
the output of the ATSC signal source (PtA in Figure A-1) to each of the
final output ports. For port 8, separate results are shown for the Pt8
and Pt8a configurations. During the measurements, all ports except that
being measured were terminated in the appropriate impedance---either 50
or 75 ohms. The response of each port was flat to well within 0.1 dB
(maximum -- minimum) across the 6-MHz bandwidth of TV channel 30. The
gain of each 75-ohm port matched that of the measurement port (Pt5a)
within 0.2 dB.

A test was also performed to determine whether frequency response on one
port would be significantly affected by impedance mismatches on other
ports, since consumer TVs may not have carefully controlled input
impedance. Figure A-4 shows three frequency response plots measured on
Port Pt5a under three different load conditions for the other eight
ports: ideal terminations (75 ohms), actual TVs (tuned to channel 30),
and open circuits. With TV's as loads the frequency response across
channel 30 remained flat to well within 0.1 dB. With open circuits on
all eight ports, flatness degraded somewhat, but was still well within
0.2 dB across channel 30.

All of the above tests were performed by using a spectrum analyzer and
tracking generator, as shown in Figure A-5. In all cases the tracking
generator signal (connected through an attenuator pad to stabilize the
impedance) was injected at PtB in Figure A-1 so that a 50-ohm source
could be used. For frequency response tests of 75-ohm ports, the losses
in TT#1, the impedance-matching transformer that normally connected the
75-ohm ATSC source to PtB, were included by using TT#1 to match the
impedance of the selected port to the 50-ohm input of the spectrum
analyzer. For frequency response tests of 50-ohm ports, TT#1 was omitted
from the measurement, but its losses as a function of frequency
(measured separately) were included in the computed frequency response.
In all cases, the tracking generator signal---as attenuated by the 10-dB
pad shown in Figure A-5---was measured by the spectrum analyzer as a
reference in the frequency response calculations. All measurements were
performed with the same spectrum analyzer settings (including input
attenuation and reference level) in order to ensure accuracy of the
computed frequency response function.)

#### Signal Spectrum, Noise Spectrum, and Signal Quality {#signal-spectrum-noise-spectrum-and-signal-quality .unnumbered}

Spectrum and modulation error ratio measurements indicate that a high
quality test signal and spectrally flat noise were delivered to the
output ports of the test setup.

Figure A-6 shows spectra of the injected signal and noise as measured at
Pt5a during playback of the "Hawaii_ReferenceA" file from the RF capture
player at a CNR of 15 dB. The spectra were measured with a 30‑kHz
resolution bandwidth, 300‑kHz video bandwidth, RMS detection, and
trace-averaging (in linear power units) of 8192 traces. (This averaging
was performed across multiple loops of the test signal). The noise
spectrum is flat across the 6‑MHz bandwidth of TV channel 30 to within
0.34 dB (maximum -- minimum) for the spectrum as shown and to within
0.11 dB when a 500‑kHz smoothing width is applied to average out some of
the randomness of the measurement. Similarly, the signal spectrum is
flat across the 4.76‑MHz wide "head" (i.e., flat part) of the ATSC
signal to within 0.59 dB for the spectrum as shown and 0.38 dB when
500‑kHz smoothing is applied.

Modulation error ratio (MER) measured by the vector signal analyzer
during the tests of required CNR was a respectable 33 to 35 dB without
including any equalization in the vector analyzer and 37 dB with
equalization.

#### Other Checks {#other-checks .unnumbered}

A test was performed to ensure that any impedance mismatch at PtC in
Figure A-1 would not affect the level of injected noise from the noise
generator through the resulting variations in impedance at the signal
input to the directional coupler as the signal step attenuator was
varied. The noise level step attenuator was adjusted to achieve -70 dBm
noise level at Pt5a. Amplifier A2 was then replaced by a short circuit
at PtC and the noise level at Pt5a was measured for two different
settings of the signal attenuator---0 dB and 81 dB. The measured
variation in noise power was only 0.01 dB.

To ensure that amplifier A2 (Figure A-1) was not operated in a
non-linear region that might affect signal quality, the signal level at
the output of A2 was measured during playback of the "Hawaii_ReferenceA"
file. The measured level was 17.5 dB below the 1-dB compression point of
the amplifier.

Signal-to-noise ratio of the signal path (excluding any noise generated
by the RF player) was measured to ensure that amplifier noise (from A1
and A2 in Figure A‑1) did not significantly affect results. SNR in a
6‑MHz bandwidth was found to be 64 dB on channel 30.

## Test Issues

A few observations regarding issues that arose during the test program
may be of value to others who perform DTV receiver performance testing.

### Multipath Performance Testing Using the RF Player

After we had tested 16 DTV receivers against each of the 47 RF captures,
visiting engineers from a DTV chipset developer (ATI Research) observed
video errors on one of the TVs during playback of a few captures. Though
all tested TVs were able to play some of the captures with no visible
errors, the visiting engineers suggested that the errors observed on
some specific captures indicated that the FCC's RF player was not
functioning properly. This conclusion was based on two factors: (1) they
had tested a TV with the same technology at their labs and found it had
produced no visible errors on those specific captures; (2) they reported
having had problems with several of their own RF capture players that
produced visible errors which went away after calibration and repair of
the player.

Based on these observations, we sent our RF player back to the
manufacturer for repair and calibration; the manufacturer indicated that
our problem had been caused by a ground plane error on one of the cards.
After they replaced that card and recalibrated the unit, the difference
was dramatic. A TV that had successfully handled only 10 of the captures
with no visible errors before the repair was able to handle 31 of the
captures without visible errors after the repair. We subsequently
discarded all previous results and repeated all testing.

As an additional confirmation of performance of our RF player---in
conjunction with our entire splitter-based test setup, ATI allowed us to
test two DTV samples (subsequently identified as "upper tier" performers
in Chapter 6) at their laboratories using their equipment. The net test
results (number of captures played with no visible errors and number
played with no more than two visible errors) at the FCC using our test
setup with our repaired RF player matched those that we performed at ATI
for one of the TVs. For the other TV, the tests at the FCC showed three
more captures producing two or fewer errors (including zero errors), but
showed two fewer captures producing no errors. Given the variability in
results that sometimes occur between playback loops along with the
subjective judgment in identifying visual errors, these differences were
considered acceptable.

### RF Source for Measurements of White Noise Threshold and of Minimum Signal

Our plan had been to use the RF player as an ATSC source only when
performing multipath testing. An ATSC signal generator was to be used
for testing of white noise threshold and of minimum signal at TOV.

In initial tests of 16 DTV receivers using the signal generator as a
source, the white noise threshold of the best tested receiver was found
to be 15.25 dB. This was slightly higher than the 14.9 to 15.0 dB that
had been expected for the better-performing receivers; consequently, the
generator was sent back to its manufacturer for calibration and
checkout. Upon its return, retesting of that best performing receiver
yielded a white noise threshold 16.0 dB---indicating degraded signal
quality.

After the poor result with the signal generator, white noise threshold
was measured again, but this time using the RF player and a
laboratory-recorded DTV signal file designated "Hawaii_ReferenceA" as
the signal source. The measured white noise threshold of that same
receiver was then found to be 14.94 dB. Based on these results, the ATSC
signal generator was replaced by the RF player, which was then used for
all testing reported herein. (Previous test results were discarded and
all tests were repeated.)

### Getting DTV Receivers to Recognize a DTV Signal

The channel-selection "intelligence" of many DTVs combined with certain
artificialities of laboratory-based testing to create some challenges.

With analog television, to receive a signal on a given TV channel you
simply select that channel. With DTV, there is another layer involved
channel selection. To simplify the DTV transition for the consumer, a
DTV signal includes coding that tells the TV the channel number of the
analog station that is associated with that DTV signal. In Washington,
DC, for example, the DTV broadcast on channel 48 includes information
linking it to an analog broadcast on channel 4. A TV viewer not aware of
the digital broadcast on channel 48 can tune to a channel he or she may
already view---channel 4---and the digital television will automatically
set its tuner to channel 48 to select the digital broadcast containing
the same programming as the viewer would have seen on analog channel 4.

To facilitate this extra layer in channel selection, DTVs include a
channel scan function that is used on initial setup of the TV. The
function causes the tuner to sequence through all TV channels searching
for analog and digital signals. It creates a mapping from the analog
channel numbers to the digital ones and may also identify available
sub-channels on each DTV broadcast, since the DTV transmission system
enables transmission of more than one program within a single RF TV
channel. Many of the TVs will not allow a DTV signal to be received
unless it has been identified by such a scan.

The laboratory tests described in this report created two types of
anomalies---one associated with the tests of minimum signal at TOV and
the other associated with multipath testing using the RF captures.

The minimum signal tests were performed on channels 3, 10, and 30. The
available equipment allowed creation of the signal on only one channel
at a time; consequently, any channel scan identified only one channel,
and when the channel was changed for the next set of tests, the channel
scan had to be repeated.

For the multipath testing, a less obvious problem occurred. All testing
was performed on channel 30, so one might expect that a single channel
scan on each TV would enable testing with all 47 captures. While this
worked for some TVs, it did not for others. The original source material
for the captures was recorded from eight DTV channels in two cities.
Many of the receivers were "confused" by changing broadcast stations
(from one capture to the next), even though the RF channel remained
constant. Many would not allow selection of the signal as channel 30;
instead, the signal had to be tuned indirectly by selecting the channel
number of the analog broadcast associated with the recorded digital
broadcast---which could only occur after a channel scan.

Thus, each time that an RF capture was loaded, if it originated from a
different broadcast station from the last, steps had to be taken to
ensure that each TV recognized the new signal. The necessary steps
varied among the TVs. Some immediately displayed the new video. For
others, simply pressing the channel up or down button caused the signal
to be selected. For TVs requiring a new channel scan, some allowed the
user to select a single channel number to rescan (channel 30 in this
case), while other required a more time consuming rescan of all
channels. For some TVs, even a complete rescan was not sufficient to
lock in the new signal; unplugging the TV from its power source followed
by a channel rescan was usually sufficient in those cases.

To save time in the multipath testing process, the captures were sorted
by originating broadcast station before testing. This reduced the number
of transitions between broadcast sources so that fewer channel scans
would be necessary. To further assist in testing, the captures were
sorted---within each originating channel group---to allow the more
benign captures from a given broadcast station to be played first in
order to lock the receivers onto each new broadcast station using a
signal for which success would be likely. It was found, however, that
during subsequent testing with captures exhibiting more challenging
multipath conditions, some TVs would change channels---or even turn
off---during the period when no recognizable signal was received.
Consequently, it was often necessary to return to an easier capture from
the same broadcast source at various times during the testing to ensure
that the TVs were still locked on to that broadcast.

## Procedures

Test procedures applicable to the DTV measurements conducted for this
report are shown below.

### General

The following procedures apply to all measurements.

1.  Warmup

    1.  Allow all test equipment (signal and noise sources, amplifiers,
        measurement equipment) to warm up for a minimum of 2 hours
        before testing.

    2.  Allow all TVs to warm up at least one hour before testing

2.  Test equipment calibration

    1.  Before each measurement sequence using the spectrum analyzer,
        perform a full alignment---including RF alignment requiring an
        external cable connection to the built in calibrated source.
        (Spectrum analyzer is used only for measurements of test
        configuration parameters such as frequency response and output
        spectrum.)

    2.  Before each measurement sequence using the vector signal
        analyzer, invoke the "single cal" function to calibrate the
        instrument.

3.  Measurement of applied signal and noise levels

    1.  Use averaging times of approximately 21 seconds (1200 averages
        on vector signal analyzer) when measuring signal levels and
        ensure that the averaging interval begins just after the start
        of a playback loop on the RF player and ends before completion
        of that loop in order to avoid averaging across the loop
        restart.

    2.  For measurements of noise levels, use averaging times ≥ 21
        seconds.

4.  Identifying visual errors in video

    1.  Allow the RF player to play the selected signal through at least
        three complete loops before making observations.

    2.  Do not count errors occurring at each loop restart of the RF
        player

    3.  Do not count errors associated with known recording defects due
        to dropped symbols (Appendix B)

    4.  Horizontal streaks occupying a single scan line are judged to be
        defects in video source material prior to conversion to MPEG
        format for broadcast and are not counted.

    5.  For an error burst lasting longer than one second, count the
        number of errors as the approximate duration of the burst in
        seconds.

### White Noise Threshold Tests

Note that all measurements are performed using the vector signal
analyzer (VSA), and all attenuator settings and measurements are entered
into a spreadsheet that performs the required computations.

1.  Connect equipment as shown in Figure A-1

2.  VSA setup

    1.  Run DTV measurement software[^38]

    2.  Set number of averages to 2000

    3.  Set broadcast channel 30

    4.  Execute "single cal"

    5.  Set amplitude range to -50 dBm (most sensitive range)

3.  RF player setup

    1.  Load "Hawaii_ReferenceA" file

    2.  Set output channel to 30

    3.  Set output level to -30 dBm

4.  Noise generator setup

    1.  Set the internal noise attenuator to 0 dB

5.  Measure VSA self noise by connecting a 50-ohm termination to the VSA
    input and performing a "long average power" measurement. (This value
    will be subtracted---in linear power units---from all subsequent
    measurements.).

6.  Connect the VSA to Pt5a (Figure A-1)

7.  Measure modulation error ratio (MER) as an indication of signal
    quality

    1.  Set noise attenuator to 81 dB

    2.  Set signal attenuator to point at which VSA indicates occasional
        clipping (typically 24 dB attenuation) in order to maximize
        signal to VSA-noise ratio

    3.  Measure MER four times and average the results. The measurements
        are performed without any equalization in the VSA.

8.  Set and measure injected noise level

    1.  Set signal attenuator to 81 dB

    2.  Adjust noise attenuator to the 0.1-dB step that most closely
        yields a "long average power" reading of -70 dBm

    3.  Measure the "long average power" twice. (Actual injected noise
        power will be computed by averaging these two measurements with
        two similar measurements performed after the TV tests and
        subtracting---in linear power units---the VSA self noise. Though
        the correction for VSA self noise is performed in the
        spreadsheet, the correction is essentially negligible because
        VSA self noise is about 27 dB below the injected noise level.)

9.  Set signal to a high level and take whatever steps are necessary to
    ensure that all connected TVs are tuned to the signal and producing
    a picture.

10. TV tests. Repeat for each of the connected TVs (typically eight).
    Include receiver D3 in each test sequence as a consistency check.

    1.  Adjust signal level upward as necessary to obtain a picture

    2.  Adjust signal level downward until picture either drops out or
        exhibits a high visual error rate

    3.  Adjust signal level upward in 0.1‑steps to achieve the lowest
        signal level that produces a picture that is free of visual
        errors for 10 seconds. Record this attenuator setting.

    4.  Adjust signal level upward in 0.1‑steps as needed to achieve the
        lowest signal level that produces a picture that is free of
        visual errors for 60 seconds. Record this attenuator setting.

        1.  As a consistency check, the spreadsheet computes difference
            between attenuator setting in previous step and current
            attenuator setting. This difference is typically between 0
            and 0.2 dB.

    5.  Perform "long average power" measurement as described below.
        This measurement represents the total of the injected signal
        level, the injected noise level (typically about 15 dB below the
        injected signal level), and the VSA self noise (typically about
        42 dB below the injected signal level).

        1.  The measurement should be initiated near the end of a
            playback loop, so that---following the initial operations
            performed when "long average power" is selected---the actual
            long integration will begin just after the start of the RF
            playback loop. The reading of average power should be taken
            just before the end of that playback loop.

        2.  As a consistency check, the spreadsheet calculates the sum
            of the signal attenuator setting and the measured power
            level. This sum should be nearly constant across all TV
            measurements.

        3.  Spreadsheet calculates injected signal level by
            subtracting---in linear power units---the injected noise
            level and the VSA self noise from the measured power. The
            injected noise level subtraction typically results in a
            correction slightly larger than 0.1 dB. The VSA self noise
            correction is negligible.

        4.  Injected signal-to-noise ratio (SNR), termed the
            carrier-to-noise ratio (CNR) in this report, is computed. (A
            subsequent adjustment is made for TV self-noise---based on
            measurements of minimum signal at TOV; however, this
            correction is essentially negligible.)

    6.  Confirm that the measured level is sufficient for relocking on
        to the DTV signal.

        1.  Reduce signal level by 20 dB for 20 seconds. Return to
            previous level and verify that the TV recaptures the signal.

    7.  Repeat steps for other TVs

11. Measure injected noise level

    1.  Set signal attenuator to 81 dB

    2.  Measure the "long average power" twice for use as described
        following 1^st^ measurements of injected noise level.

Because both the injected noise power measurement and the injected
signal measurement were performed using the same vector signal analyzer
on the same amplitude range, the CNR is expected to be quite accurate,
since it doesn't depend on the absolute calibration accuracy of the
measuring instrument.

Additional information on the testing is included in the "Measurement
Method" section of Chapter 3.

### Minimum Signal Tests

Note that all measurements are performed using the vector signal
analyzer (VSA), and all attenuator settings and measurements are entered
into a spreadsheet that performs the required computations. The tests
are performed for TV channels 3, 10, and 30.

12. Connect equipment as shown in Figure A-2.

13. VSA setup

    1.  Run DTV measurement software[^39]

    2.  Set number of averages to 1200

    3.  Set selected broadcast channel

    4.  Execute "single cal"

    5.  Set amplitude range to -50 dBm (most sensitive range)

14. RF player setup

    1.  Load "Hawaii_ReferenceA" file

    2.  Set output channel to selected channel

    3.  Set output level to -30 dBm

15. Measure VSA self noise three times by connecting a 50-ohm
    termination to the VSA input and performing a "long average power"
    measurements. (The average of these measurements will be
    subtracted---in linear power units---from all subsequent
    measurements.)

16. TV tests. Repeat for each of TV to be tested (typically eight).
    Include receiver D3 in each test sequence as a consistency check.

    1.  Connect output of the test setup through impedance-matching pad
        MLP#12, as shown by the solid lines on the right side of Figure
        A-2.

    2.  Set signal to a high level and take whatever steps are necessary
        to ensure that TV is tuned to the signal and producing a
        picture.

    3.  Adjust signal level downward until picture either drops out or
        exhibits a high visual error rate

    4.  Adjust signal level upward in 0.1‑steps to achieve the lowest
        signal level that produces a picture that is free of visual
        errors for 10 seconds. Record this attenuator setting.

    5.  Adjust signal level upward in 0.1‑steps as needed to achieve the
        lowest signal level that produces a picture that is free of
        visual errors for 60 seconds. Record this attenuator setting.

        1.  As a consistency check, the spreadsheet computes difference
            between attenuator setting in previous step and current
            attenuator setting. This difference is typically between 0
            and 0.2 dB.

    6.  Perform "long average power" measurement as described below.

        1.  The measurement should be initiated near the end of a
            playback loop, so that---following initial operations
            performed when "long average power" is selected---the actual
            long integration will begin just after the start of the RF
            playback loop. Confirm that the integration ends before
            completion of the playback loop.

        2.  As a consistency check, the spreadsheet calculates the sum
            of the signal attenuator setting and the measured power
            level. This sum should be nearly constant across all TV
            measurements.

        3.  Spreadsheet calculates injected signal level by
            subtracting---in linear power units---the VSA self noise
            from the measured power (a correction that is typically less
            than 0.1 dB) and then subtracting (in dB) the power loss of
            impedance-matching pad MLP#12 for the specific TV channel
            tested.

    7.  Repeat steps for other TVs

Additional information on the testing is included in the "Measurement
Method" section of Chapter 4.

### Multipath Tests (RF Captures)

Note that in-band injected signal power (6-MHz bandwidth centered at
channel 30) was measured at Pt5a (Figure A‑1) using the vector signal
analyzer (VSA) for each of the 47 RF captures during tests of the first
group of eight receivers. These measurements were not repeated for
subsequent receivers because small variations in absolute signal level
applied to the receivers were not expected to affect the results.

17. Connect equipment as shown in Figure A-1

18. VSA setup

    1.  Run DTV measurement software[^40]

    2.  Set number of averages to 2000

    3.  Set broadcast channel 30

    4.  Execute "single cal"

    5.  Set amplitude range to -20 dBm

19. RF player setup

    1.  Set output channel to 30

    2.  Set output level to -30 dBm

20. Signal and noise attenuators

    1.  Set signal attenuator to 0 dB. This was found to provide a
        median in-band signal power of ‑29.7 dBm across the 47 RF
        captures. This is 53 dB above the minimum signal level at TOV
        for typical receivers; consequently, any variations in absolute
        level among the captures was not expected to affect the test
        results.

    2.  Set the noise attenuator to 81 dB to effectively eliminate
        injected noise.

21. Measure modulation error ratio (MER) as an indication of signal
    quality.

    1.  Load "Hawaii_ReferenceA" file

    2.  In the first series of tests, MER was measured twice with
        internal equalizer off. The average of the measurements was 35.5
        dB.

22. Tests for a given capture\
    (Note that captures are loaded and tested sequentially in groups for
    which the originating TV broadcast channel is the same. Within each
    group, captures that are deemed to be easier to acquire---due to
    benign multipath conditions---are loaded first to increase the
    likelihood of a successful channel scan on each TV.)

    1.  Load the selected RF capture

    2.  Ensure signal acquisition for all TVs, to the extent possible

        1.  If this capture corresponds to a different broadcast TV
            channel than the last capture, take whatever steps are
            necessary to ensure that all connected TVs are tuned to the
            signal and have an opportunity to produce a picture. This
            may include channel scans or disconnecting power. To improve
            probability of success, the first capture loaded should have
            as benign multipath conditions as possible.

        2.  If this capture corresponds to the same broadcast TV channel
            as the last, then check to see that all TVs have acquired
            the signal (i.e., are producing a TV picture). If not, try
            channel scans or returning to a more benign capture from the
            same broadcast channel to achieve acquisition.

    3.  Wait for at least three full playback loops to be completed
        before judging TV receiver performance.

    4.  TV tests. Repeat for each of the connected TVs (typically
        eight). Include receiver D3 in each test sequence as a
        consistency check.

        1.  Observe video on the selected TV and count the number of
            video errors observed during a single playback loop. If
            performance is monitored over several loops and, if the
            results vary, select the median number of errors as the
            value to record. A video error burst lasting more than one
            second is counted based on the approximate duration in
            seconds. Thus, an error burst lasting three seconds is
            counted as three errors. Errors occurring during or
            immediately after the loop-restart time are not counted, nor
            are errors associated with known defects (dropped symbols)
            in eight of the captures, as documented by the ATSC.[^41]

        2.  Repeat for next TV

    5.  Repeat for next RF capture

Additional information on the testing is included in the "Measurement
Method" section of Chapter 4.

## Equipment

Table A-1 identifies the equipment used for the tests that were
conducted for this report.

[]{#__RefHeading___Toc118693192 .anchor}Table A‑1. Equipment List

+--------+-------+-----------+-----------+-------+-------------------+
| **     | **MO  | **EQ      | **S/N**   | **CAL | **USE**           |
| MAKE** | DEL** | UIPMENT** |           | D     |                   |
|        |       |           |           | ATE** |                   |
+--------+-------+-----------+-----------+-------+-------------------+
| S      | R     | RF Player | 007, Run  | 8/    | ATSC source for   |
| encore | FP910 |           | 11A       | 10/05 | all tests         |
+--------+-------+-----------+-----------+-------+-------------------+
| A      | 8     | Vector    | U         | 9/    | CNR measurements  |
| gilent | 9441A | Signal    | S40514809 | 17/04 | before 8/30/05;   |
|        |       | Analyzer  | /U        |       |                   |
|        |       |           | S39313048 |       | amplitude of      |
|        |       |           |           |       | injected captures |
|        |       |           |           |       | before 8/30/05    |
+--------+-------+-----------+-----------+-------+-------------------+
| A      | 8     | Vector    | U         | 8     | CNR measurements  |
| gilent | 9441A | Signal    | S40514815 | /8/05 | after 8/30/05;    |
|        |       | Analyzer  | /U        |       |                   |
|        |       |           | S39313021 |       | All minimum       |
|        |       |           |           |       | signal            |
|        |       |           |           |       | measurements      |
+--------+-------+-----------+-----------+-------+-------------------+
| A      | E     | Spectrum  | U         | 10/   | Calibration of    |
| gilent | 7405A | Analyzer  | S41160406 | 27/04 | minimum-loss      |
|        |       |           |           |       | i                 |
|        |       |           |           |       | mpedance-matching |
|        |       |           |           |       | pads (6/7/05)     |
+--------+-------+-----------+-----------+-------+-------------------+
| A      | E     | Spectrum  | U         | 8/    | Frequency         |
| gilent | 7405A | Analyzer  | S41160425 | 16/05 | response of       |
|        |       |           |           |       | splitter test     |
|        |       |           |           |       | configuration     |
+--------+-------+-----------+-----------+-------+-------------------+
| Noi    | UFX   | Noise     | P292-0135 | \*\*  | Noise source for  |
| se/Com | -7110 | Generator |           |       | white-noise       |
|        |       |           |           |       | threshold tests   |
+--------+-------+-----------+-----------+-------+-------------------+

Notes:\
\*\* Last factory calibration was 8/21/01, but for the reported tests,
output was calibrated by means of Agilent E7405A spectrum analyzer at
the time of each test.

![](media/image17.wmf){width="5.9944444444444445in"
height="3.3756944444444446in"}

[]{#__RefHeading___Toc118693155 .anchor}Figure A‑1. Block Diagram of
Test Configuration for Required CNR and RF Capture Tests

![](media/image18.wmf){width="5.997916666666667in"
height="1.7006944444444445in"}

[]{#__RefHeading___Toc118693156 .anchor}Figure A‑2. Block Diagram of
Test Configuration for Minimum Signal at TOV

![](media/image19.wmf){width="6.497916666666667in"
height="4.261111111111111in"}

[]{#__RefHeading___Toc118693157 .anchor}Figure A‑3. Frequency Response
of Each Port

![](media/image20.wmf){width="6.497916666666667in"
height="4.267361111111111in"}

[]{#__RefHeading___Toc118693158 .anchor}Figure A‑4. Effect of Load
Impedance Mismatch

![](media/image21.wmf){width="4.550694444444445in"
height="1.0229166666666667in"}

[]{#__RefHeading___Toc118693159 .anchor}Figure A‑5. Calibration
Connection for Test Setup for Required CNR and RF Capture Tests

![](media/image22.wmf){width="6.497916666666667in"
height="4.4430555555555555in"}

[]{#__RefHeading___Toc118693160 .anchor}Figure A‑6. Spectra of Injected
Signal and Noise at 15-dB CNR

#######  SUMMARY OF RF FIELD CAPTURES

Table B-1 lists the 50 ATSC-recommended captures, some of their
characteristics, and the number of consumer DTV receivers (of 28) that
successfully demodulated each capture in tests for this report.

The three captures having no video content (e.g., grey or black screens)
were not tested, except with an instrumented receiver which is not
included in the tabulated results. In counting observed video errors,
errors coinciding with the locations of known symbol drops, as reported
by the ATSC, were not counted. Note that four of the captures on which
no tested receiver achieved demodulation free of visual errors were
identified by the ATSC as having possible non-linearities caused by
high-level adjacent channels overdriving the recording system.

Notes on Table B-1 (next page):

All captures have durations of 23 or 25 seconds

\* Site: HR = high rise apartment; SF = single family home; TH =
townhouse

Antenna: ID = indoors at 6-ft height; OD = outdoors at 30-ft height

\*\*Issues: DS = 48 dropped symbols at specified location; NL =
recording may contain nonlinearities due to strong adjacent channel

[]{#__RefHeading___Toc118693193 .anchor}Table B‑2. RF Field Captures

  ------ --------------------------- ------ ----------- ---------- ------------ ----------- -----------
  File   Original data capture       Chan   Site /      Distance   Known        \# of       \# of
  \#     filename                           Antenna\*   from Tx    Issues\*\*   Receivers   Receivers
                                                        (Miles)                 w/No Errors w/≤2 Errors

  01     NYC_200_44_10272000_DBT1    44     HR / ID     2.0                     10          10

  02     NYC_200_44_10272000_LOOP1   44     HR / ID     2.0                     0           0

  03     NYC_200_44_10272000_MEGA1   44     HR / ID     2.0                     10          10

  04     NYC_200_44_10272000_RAB1    44     HR / ID     2.0                     10          10

  05     NYC_200_44_10272000_SSEN1   44     HR / ID     2.0                     10          10

  06     NYC_200_44_10272000_SSEN2   44     HR / ID     2.0                     10          10

  07     NYC_200_44_10272000_SSEN3   44     HR / ID     2.0                     0           0

  08     NYC_200_44_10272000_YAGI1   44     HR / ID     2.0                     13          13

  09     NYC_200_56_10272000_BWT1    56     HR / ID     2.0                     2           10

  10     NYC_200_56_10272000_DBT2    56     HR / ID     2.0                     10          10

  11     NYC_200_56_10272000_DSEN1   56     HR / ID     2.0                     10          10

  12     NYC_200_56_10272000_DSEN2   56     HR / ID     2.0                     1           14

  13     NYC_200_56_10272000_LOOP1   56     HR / ID     2.0                     10          10

  14     NYC_200_56_10272000_MEGA1   56     HR / ID     2.0                     11          11

  15     NYC_200_56_10272000_RAB1    56     HR / ID     2.0                     10          10

  16     NYC_200_56_10272000_SSEN1   56     HR / ID     2.0                     0           10

  17     NYC_200_56_10272000_YAG1    56     HR / ID     2.0                     10          10

  18     WAS_06_34_06092000_REF      34     SF / OD     10.8                    8           10

  19     WAS_23_34_06072000_OPT      34     SF / ID     16.7                    28          28

  20     WAS_23_48_06072000_OPT      48     SF / ID     15.5                    0           8

  21     WAS_3_27_06022000_REF       27     SF / OD     48.4                    9           13

  22     WAS_3_35_06022000_REF       35     SF / OD     51.9       No Video     NA          NA

  23     WAS_311_34_06052000_OPT     34     HR / ID     4.3        NL           0           0

  24     WAS_311_35_06052000_REF     35     HR / OD     3.9        No Video     NA          NA

  25     WAS_311_36_06052000_REF     36     HR / OD     4.7                     13          14

  26     WAS_311_39_06052000_OPT     39     HR / ID     4.3                     0           0

  27     WAS_311_48_06052000_REF     48     HR / OD     3.9                     2           11

  28     WAS_32_48_06012000_OPT      48     SF / ID     17.8       NL           0           0

  29     WAS_34_27_06082000_OPT      27     TH / ID     7.5                     7           27

  30     WAS_34_35_06082000_OPT      35     TH / ID     9.6        NL           11          13

  31     WAS_34_48_06082000_OPT      48     TH / ID     9.6                     7           11

  32     WAS_38_34_05312000_OPT      34     TH / ID     14.3       DS@15.0 sec  26          26

  33     WAS_38_34_05312000_REF      34     TH / OD     14.3       DS@15.1 sec  27          28

  34     WAS_38_36_05312000_OPT      36     TH / ID     14.3       DS@22.2 sec  24          24

  35     WAS_47_48_06132000_OPT      48     SF / ID     13.1       DS@13.8 sec  27          28

  36     WAS_49_34_06142000_OPT      34     SF / ID     20.2       Possible DS  0           0

  37     WAS_49_39_06142000_OPT      39     SF / ID     20.2       DS@24.9 sec  10          11

  38     WAS_51_35_05242000_REF      35     SF / OD     20.3                    8           8

  39     WAS_63_34_06212000_OPT      34     SF / ID     12.7                    0           9

  40     WAS_68_36_05232000_REF      36     SF / OD     17.7       NL           0           8

  41     WAS_75_35_06162000_OPT      35     SF / ID     10.0                    0           1

  42     WAS_75_36_06162000_OPT      36     SF / ID     10.9       NL           0           0

  43     WAS_75_39_06162000_OPT      39     SF / ID     10.5                    10          13

  44     WAS_80_35_06152000_OPT      35     TH / ID     9.9        No Video     NA          NA

  45     WAS_81_36_06192000_OPT      36     SF / ID     9.6                     12          27

  46     WAS_82_35_06202000_OPT      35     SF / ID     8.3        DS@17.2 sec  27          28

  47     WAS_83_36_06222000_OPT      36     TH / ID     3.5        DS@14.9 sec  2           5

  48     WAS_83_39_06222000_OPT      39     TH / ID     3.0        DS@12.2 sec  28          28

  49     WAS_86_36_07122000_OPT      36     SF / ID     33.3                    10          10

  50     WAS_86_48_07122000_REF      48     SF / OD     34.4                    1           5
  ------ --------------------------- ------ ----------- ---------- ------------ ----------- -----------

See notes on preceding page

[^1]: 8-level Vestigial Side Band (8-VSB) is the over-the-air digital
    television (DTV) transmission format recommended by the Advanced
    Television Systems Committee (ATSC) and adopted by the FCC as the
    U.S. standard for terrestrial DTV transmission.

[^2]: 8-level Vestigial Side Band (8-VSB) is the over-the-air digital
    television (DTV) transmission method recommended by the Advanced
    Television Systems Committee (ATSC) and adopted by the FCC as the
    U.S. standard for terrestrial DTV transmission.

[^3]: Citta, Richard, and Sgrignoli, Gary, "ATSC Transmission System:
    VSB Tutorial", Montreuz Symposium, June 12, 1997, p.8.

[^4]: Sgrignoli, Gary, "Interference Analysis of Co-Sited DTV and NTSC
    Translators", IEEE Transactions on Broadcasting, Vol. 51, No. 1,
    March 2005, p.3.

[^5]: Eilers, Carl, and Sgrignoli, Gary, "Digital Television
    Transmission Parameters\-- ATSC Compliance Factors", IEEE
    Transactions on Broadcasting, Vol. 45, No. 4, December 1999, p.12.

[^6]: Laud, Tim, Aitken, Mark; Bretl, Wayne; and Kwak, K. Y.,
    "Performance of 5th Generation 8-VSB Receivers", IEEE Transactions
    on Consumer Electronics, Vol. 50, No. 4, November 2004.

[^7]: "ATSC Recommended Practice: Receiver Performance Guidelines", ATSC
    Doc. A/74, Advanced Television Systems Committee, 17 June 2004,
    p.24.

[^8]: Final Technical Report, FCC Advisory Committee on Advanced
    Television Service's (ACATS), October 31, 1995, p.15 (Table 5.1).

[^9]: "ATSC Recommended Practice: Receiver Performance Guidelines", ATSC
    Doc. A/74, Advanced Television Systems Committee, 17 June 2004.

[^10]: The vector signal analyzer specification sheet states that
    relative accuracy in RF vector mode on a single range is the sum of
    frequency response and amplitude linearity. If we ignore the
    frequency response term because the measurements are made over the
    same frequency range, we are left with the amplitude linearity term,
    which is specified as "\<0.1 dB" for signal levels between 0 dB and
    -30 dB with respect to full scale---a condition that was met by both
    the signal and injected noise measurements. To this we add errors
    caused by the 0.1‑dB attenuator step size.

[^11]: Span does not match difference between worst and best due to
    rounding of all numbers to nearest 0.1 dB.

[^12]: As an additional check on equipment performance, measurements of
    injected broadband signal level and of injected broadband noise
    level---at levels typical of those used for white-noise threshold
    testing (-70 dBm for noise and -55 dBm for signal---both measured
    across the 6-MHz bandwidth of TV channel 30)---were performed using
    two instruments, the vector signal analyzer and a spectrum analyzer
    (Agilent E7405A). The spectrum analyzer measurements were made with
    the internal preamp on and the internal attenuation set to 0 dB. The
    spectrum analyzer overall amplitude accuracy is specified as "±(0.54
    dB + absolute frequency response)" with the absolute frequency
    response being specified as ±0.5 dB over the frequency range of
    interest. For both signal and noise, the spectrum analyzer
    measurements were 0.1 dB higher than the vector signal analyzer
    measurements---suggesting that both instruments (which were
    calibrated no more than two months before the measurements reported
    in this chapter) were likely performing well within the specified
    tolerances. (Note that self calibrations were also performed on both
    instruments before each set of measurements.)

[^13]: "*ATSC Recommended Practice: Receiver Performance Guidelines*",
    ATSC Doc. A/74, Advanced Television Systems Committee, 17 June 2004,
    p.11.

[^14]: See note for Table 1-1.

[^15]: Absolute measurement accuracy of the vector signal analyzer on
    the amplitude range that was used for the measurements was as ±1.5
    dB maximum and ±0.5 dB typical.

[^16]: As is explained in Chapter 3, the statistical assessment
    performed above is dependent upon a number of assumptions that are
    not strictly true for the case at hand. Arguably, the most
    questionable of these is the assumption that the performance of the
    each receiver sample is independent of the others. It is quite
    likely that some of the receiver samples share critical subsystems,
    which would violate the independence assumption. For example a given
    tuner or demodulator design may be used in more than one of the
    receivers. The effect of such a commonality between samples would be
    to decrease the effective number of degrees of freedom in the
    computed Pearson's correlation coefficient. Such a decrease would
    increase the magnitude of correlation that would have to be observed
    to have a given confidence level in the result. Taking this effect
    into account would further diminish any statistical significance of
    the results.

[^17]: Various receiver design anomalies could result in reception
    sensitivity being limited by factors other than receiver noise
    (noise figure). For example, if the AGC (automatic gain control)
    does not allow sufficient RF and IF gain to amplify a weak signal to
    the level necessary for demodulation, reception performance will be
    limited by gain rather than by amplifier noise. Similarly, receiver
    performance could also be limited by local oscillator phase noise or
    by leakage into the tuner of internally-generated interference
    sources such as impulse noise from digital circuits or narrowband
    (tonal) interference.

[^18]: The reference temperature is generally taken as the antenna
    temperature. 290°K = 17°C = 62°F results in a thermal noise level
    matching the -106.2 dB value used in OET‑69.

[^19]: Absolute measurement accuracy of the vector signal analyzer on
    the amplitude range that was used for the measurements was as ±1.5
    dB maximum and ±0.5 dB typical.

[^20]: *"ATSC Recommended Practice: Receiver Performance Guidelines"*,
    ATSC Doc. A/74, Advanced Television Systems Committee, 17 June 2004.

[^21]: Ibid., p. 15.

[^22]: See Table B-1 of this report or the "Quality of Capture" column
    of the continuation of Figure A-1 on p.28 of *"ATSC Recommended
    Practice: Receiver Performance Guidelines"*, ATSC Doc. A/74,
    Advanced Television Systems Committee, 17 June 2004.

[^23]: The Program and System Information Protocol (PSIP) includes a
    field for establishing this association. Further information is
    available in Advanced Television Systems Committee documents A/65B
    "*ATSC Standard: Program and System Information Protocol
    forTerrestrial Broadcast and Cable (Revision B)*" and A/69 "*ATSC
    Recommended Practice: Program and System Information Protocol
    Implementation Guidelines for Broadcasters" for more information*."

[^24]: Receiver D1 belongs in the "lower tier+" category because it
    performed above the range of performance for the lower tier both in
    terms of number of captures played with no errors and number of
    captures played with two or fewer errors. The case for placing
    receiver L2 in the "lower tier+" category rather than in the lower
    tier is weaker, since only one of its performance numbers (number of
    captures played with two or fewer errors) was above the lower tier
    range.

[^25]: With 8-VSB, each transmission segment consists of one MPEG
    packet. Thus, a segment error is equivalent to an MPEG packet error.

[^26]: In general, visual errors are expected to occur only when segment
    errors occur, but the reverse is not always true, depending on
    effectiveness of MPEG error concealment algorithms for the video
    content at the time of the errors.

[^27]: One of the tested set-top-box models was released to the market
    in August 2003. The other four were released between July and
    November 2004.

[^28]: 15.3 dB is the median value for those receivers identified as
    lower tier---not including those identified as "lower tier+". If the
    lower tier+ receivers are included, the median is 15.4 dB.

[^29]: "Final Technical Report", Federal Communications Commission
    Advisory Committee on Advanced Television Service (ACATS), October
    31, 1995, p.19.

[^30]: Inglis, William H. and Means, David L., *"A Study Of ATSC (8-VSB)
    DTV Coverage In Washington, DC,*

    *And Generational Changes In DTV Receiver Performance"*, Interim OET
    Report FCC/OET TRB-00-2, Technical Research Branch, Laboratory
    Division, Office of Engineering and Technology, Federal
    Communications Commission, April 9, 2001.

[^31]: More specifically, 200 sites were randomly selected within the
    17.5-mile box. The tested sites were selected from among
    these---focusing on sites located in Washington, DC and sites near
    the FCC Laboratory, in Columbia, MD.

[^32]: With the mast-mounted antenna, 51 sites were tested. With the
    tripod-mounted antennas, 50 sites were tested. In both cases, all
    but one site had sufficient field strength for theoretical DTV
    reception.

[^33]: Out of the 50 sites that had sufficient field strength for
    theoretical DTV reception.

[^34]: The indoor antenna was mounted at a 7-foot height, consistent
    with indoor antenna, but tests were performed outdoors.

[^35]: "ATSC Recommended Practice: Receiver Performance Guidelines",
    ATSC Doc. A/74, Advanced Television Systems Committee, 17 June 2004,
    p.11.

[^36]: See note for Table 1-1.

[^37]: The intent was both to minimize standing waves on the 25-foot,
    low-loss cables and to reduce the impact of RF energy reflected back
    from a poorly matched TV on signals delivered to other TVs through
    the splitter.

[^38]: \"Control Software for the HP89400 Vector Signal Analyzer for
    Measuring DTV and NTSC Signals\", VSA5.BAS, Version 5.02, Gary
    Sgrignoli

[^39]: \"Control Software for the HP89400 Vector Signal Analyzer for
    Measuring DTV and NTSC Signals\", VSA5.BAS, Version 5.02, Gary
    Sgrignoli

[^40]: \"Control Software for the HP89400 Vector Signal Analyzer for
    Measuring DTV and NTSC Signals\", VSA5.BAS, Version 5.02, Gary
    Sgrignoli

[^41]: See Table B-1 in Appendix B of this report, or the "Quality of
    Capture" column of the continuation of Figure A-1 on p.28 of *"ATSC
    Recommended Practice: Receiver Performance Guidelines"*, ATSC Doc.
    A/74, Advanced Television Systems Committee, 17 June 2004.