SPAN = 2 MHz / Div VERT = 10 db / div
90% of the transmitted power
(enhanced area) should fall within 5.39 MHz
HDTV Primer
THE FCC GIVES YOU THE RIGHT TO INSTALL A TV ANTENNA OR SATELLITE DISH (Click Here)
What is HDTV?
HDTV is high-resolution Digital Television (DTV) combined with Dolby Digital surround sound (AC-3) that allows you to FEEL THE SOUND. This combination creates a vastly superior image with state of the art sound. HDTV requires new production and transmission equipment for the Broadcaster, as well as new equipment for reception by the consumer.
The higher resolution picture is the main selling point for HDTV. Imagine 720 or 1080 lines of resolution compared to the 525 interlaced lines of the 50+ year old NTSC standard still used in the U.S. by some broadcasters, and also for older VHS tape players, older camcorders, etc. Basically, the pixel count is about 211,000 for NTSC, compared to over 2,000,000 pixels for HDTV.
Plasma and LCD television receivers reproduce about 33% of the total colors that the eye can see. Laser and LED TVs are technically superior, and produces virtually all of the total color bandwidth that the human eye can see. LED TV is clearer and more brilliant, and draws a fraction of the electricity required by older Plasma and LCD technology.
The lowest resolution computer monitor has increased from typically 640 x 480 in 1984, to 800 x 600 in 1990, to 1024 x 768 in 2000, and even higher today, with a much higher refresh rate. Television is following the same path, with refresh rates of 240 or 600 per second becoming common.
The horizontal resolution for a state of the art NTSC color TV is typically 400 dots or less, but you're lucky to see 330, and even less with a VHS Tape (about 240 horizontal lines).
NTSC (old TV broadcast standard) takes the simultaneous output of the RED, GREEN, and BLUE video information from an NTSC Studio Television Camera (which has bandwidth of between 5 to 6 MHz of information for each of the 3 primary colors, and serializes it by encoding it into an NTSC format for transmission to your TV. It is then "decoded" by your TV, and the result is applied in parallel to the proper RED, GREEN, and BLUE dots (or stripes) to reproduce the color picture. The problem with NTSC is that only the GREEN video channel provides the "detail" for the picture (Y, or luminance information). Unfortunately, the Y channel is limited to a bandwidth of around 3 MHz., and the color information is "added" (in very low resolution) as subcarrier information (R minus Y, or B minus Y) that is only 500 KHz wide (from 3.7 MHz to 4.2 MHz), with a "Pilot" (reference lock) Frequency (burst) of 3.579545 MHz.
HDTV has about 5 times more detail per pixel than NTSC. HDTV starts off with typically 30 MHz Bandwidth for each RED, GREEN, and BLUE video channel, and each channel contributes and provides a Y (luminance) channel with excellent detail, plus the R-Y, and B-Y lower bandwidth signals (1/2 the bandwidth of the Y Channel, contain many times more information than the old analog NTSC color encoding. While "black" may be represented in NTSC as "0 IRE [above setup], it is represented as HEX200 (data value) in a chroma channel at baseband (If R-Y / B-Y component drops to "zero," the picture will appear GREEN).
The 2 most common of the 18 different 1996 FCC approved DTV formats are:
NOTE: The higher the frame rate, the clearer the picture is for moving subjects. Still images appear sharper with higher pixel formats, and lower frame rates.
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720p: 1280 x 720 pixels progressive scan, 829,000 displayable pixels per frame - used by ABC and FOX - TV Networks- .
- 1080i: 1920 x 1080 pixels interlaced scan - used by CBS, NBC, and PBS - TV Networks
NOTE2: A cost-effective way to receive DTV signals is to use your computer with WinTV's DTV Tuner, but the HiPIX - 200 card also allows you to RECORD Digital TV Programs on your computer.
| An HDTV antenna system is very critical.
Do NOT use a 300 ohm antenna wire.
Replace it with a AVOID USING AN ANTENNA WITH A BUILT-IN YOU MUST TERMINATE ALL UNUSED RF AND VIDEO |
The HDTV signal coming into your house starts off with an MPEG encoder, a device that generates only the difference information between two sequential video frames.
At the network, Standard Definition video data is generated using a data stream of 270 Mb/s., while an HDTV Data Stream is 1.485 Gigabits /s. This can be compressed to 45 Mb/s to accommodate the bandwidth limitation of Ku Band Satellites, for program distribution to the affiliate station in your city.
Your local station receives this data stream, and processes it into an HDTV signal for distribution on its channel by converting it with an MPEG-2 encoder with a data rate output of 19.39 Mb/s.
The HDTV encoder circuit then takes this signal and adds framing information, and randomizes the data to smooth it out over the transmitted bandwidth. Next the data stream is subjected to more encoding which breaks the stream into packets. Then the signal is further broken up into a series of "words" that incorporate error correction.
A series of sync signals is then mixed with the data stream-- segment sync, field sync, and the ATSC Pilot. The resulting signal is applied to an 8-VSB modulator (8 Level Vestigal Side Band), which provides the finished HDTV baseband signal.
The HDTV Baseband Signal is then sent by a microwave Studio-Transmitter Link (STL) or Fiber Optic Link (FOL), from the Studio to the Transmitter Site. The HDTV Baseband Signal is then up-converted to the desired TV Channel, amplified to a much higher power level, and transmitted VIA the Station's Antenna.
A good HDTV transmit system will have an envelope with 90% of the transmitted power contained within 5.39 MHz of its 6 MHz wide TV Channel. The ATSC Pilot can be readily seen as a spike on a spectrum analyzer in the top left corner of the transmitted envelope. The ATSC Pilot is responsible for about 7% of the total power of a transmitted HDTV signal.
Due to the nature of Digital Transmission (no carrier, et), HDTV reportedly needs less than 1/10th the transmitter power of an NTSC station for a 99% market coverage. An interesting note is that the HDTV modulation process tries to distribute the data evenly over the 5.39 MHz bandwidth , but power peaks can sometimes exceed 4 TIMES the average power output, using 8-VSB Modulation!
"Re-Clocking DAs" can prevent cliff effects at the data level, in complex digital video distribution systems (similar to a proc amp in an analog video system).
Detailed HDTV Encoding Information from ZENITH™
Detailed 8-VSB Transmission & HDTV Encoding from HARRIS™
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Arcing across Power Line insulators and components can generate Radio Frequency "noise" that cause digitally broadcast pictures to freeze or pixelate.