Specifications

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Linear Audio / Video / Data Solutions
72 Application Diagrams
Frequently Asked Questions About
DTV-Compatible Amplifiers
Q. Can I use Linear’s amplifiers to distribute DTV?
A. Yes, Linear’s DA series amplifies all video signals between
54 MHz and 1 GHz. Television, including DTV, is broadcast
between 55 MHz and 800 MHz. Our new generation of
amplifiers increases headroom to reduce distortion and
accommodates digital signals. In addition, they offer more
robust power and greater EMI rejection.
Q. When do I use a bi-directional (BID) amplifier and
when do I use a high headroom (HHR) amplifier?
A. Either amplifier can be used with DTV. The BID amplifier
has a 5–42 MHz return path designed for cable modems
and interactive cable boxes (pay-per-view). Use the HHR
amplifier for installations where an antenna is being used.
Q. When is Linear going to make a DTV modulator?
A. A modulator is not needed for “off-the-air” DTV.
Modulators are only used to distribute local video sources.
Currently, there are no video sources that provide the
ATSC (DTV) data stream. When DVD players or VCRs that
generate HDTV signals become available, we will design a
solution to distribute them.
Q. How do NTSC and DTV differ?
A. NTSC and DTV differ in picture format, lines of
resolution, modulation methods when transmitted,
and audio encoding.
NTSC is an analog RF transmission with a picture format
of 4:3. The resolution rate is 525 lines with 480 lines of
active interlaced material. Interlaced means that the 480
lines are divided into two fields; even numbered lines are
transmitted during field one and odd numbered lines are
transmitted during field two. Each field is drawn on the
screen every 60th of a second, this is known as 480i. The
audio is transmitted using MTS stereo and Dolby
Pro Logic
®
.
DTV or ATSC is a digital video standard and is transmitted
using 8VSB modulation. There are 18 variations on the
standard, with many having an aspect ratio of 16:9. All
DTV tuners are compatible with all 18 standards. The
three main standards include 480p, 720p, and 1080i. The
480p and 720p are progressive formats, which allows
the entire picture to be drawn in a single pass. The 1080i
is interlaced and, like NTSC, is drawn in two passes of
two separate fields. Only the 720p and, 1080i displayed
in a 16:9 format are considered to be true HDTV. 480p
is considered standard television (SDTV). The audio is
encoded using Dolby Digital, offering up to 5:1 channels of
digital sound.
50
100
150
200
250
300
350
400 450
500 550
600
650
700 750
800
2–6
UHF
ULTRA bandSUPER
band
23–36
HYPER
band
7–13
14–22 37– 64
65–125
Amplifiers
7–13
14–69
54 MHz–1 GHz
OFF-AIR
BAND
CHANNEL
NUMBER
FREQUENCY
MHz
CABLE
BAND
CHANNEL
NUMBER
VHF
low
MID
band
VHF
high
14–69
VHF
high
7–13
2–6
VHF
low
2–6