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NTSC & DTV Comparison• NTSC was fully analog
• Amplitude Modulation (with vestigial sideband) for visual content• Upper sideband used for majority of picture information – not suppressed carrier• Lower sideband – most of content removed, but some (vestige) left – thus VSB
• (Reason was high quality filtering had not been developed that early)• Frequency Modulation for aural content• 25 KHz deviation (FM broadcast is 75 KHz deviation)• Stereo developed in 1980s (BTSC)• Aural carrier typically 10% of visual carrier amplitude (average vs. peak)• Most receivers used inter-carrier demodulation of the aural carrier – used the
precise 4.5 MHz difference between visual and aural carriers. That required that there always be some amount of the visual carrier present, or the audio would buzz.
• ATSC is fully digital• Amplitude Modulation for all content• 8 levels of Amplitude Modulation – 8VSB• Video, audio, PSIP, other data all multiplexed into one stream• 10.76 megabaud; gross bit rate of 32Mb/s; net bit rate of 19.39 Mb/s• 19.39 Mb/s transmitted within one 6 MHz RF channel• http://www.arrl.org/files/file/Technology/TV_Channels/8_Bit_VSB.pdf
NTSC & DTV Comparison316 KW ERP
31.6 KW ERP
NTSC & DTV Comparison
55 KW ERP (average)
NTSC & DTV Comparison
KERA-TV Channel 13Physical Ch 14, Virtual Ch 13
Physical Channels vs. Virtual Channels• The RF channel may or may not be the same as the
virtual channel• Most stations kept their original analog channel
number as their virtual channel for branding continuity
• This is because PSIP (Program and System Information Protocol) makes it irrelevant to the viewer
• DTV receivers will scan the channels and generate a table that associates virtual channels with physical channels
Studio End
Transmitter End
Dallas/Fort Worth DTV StationsStation Vir. Chan RF. Chan Freq Programs Streams
KDTN 2 43 647 2.1 1
KDFW 4 35 599 4.1 1
KXAS 5 41 635 5.1, 5.2 2
WFAA 8 8 183 8.1, 8.2, 8.3 3
KTVT 11 19 503 11.1, 11.2 2
KERA 13 14 473 13.1, 13.2 2
KPFW-LD 18 18 497 18.1, 18.2, 18.3, 18.4 4
KBOP-LD 20 20 509 20.1, 20.2, 20.3, 20.4 4
KTXA 21 29 563 21.1, 21.2 2
KUVN 23 23 527 23.1, 23.2, 23.3, 23.4 4
K25FW 25 25 539 25.1 1
KODF-LD 26 27 551 26.1, 26.2, 26.3, 26.4 4
KDFI 27 36 605 27.1, 27.2, 27.3 3
Station Vir. Chan RF. Chan Freq Programs Streams
KHPK-LD 28 28 557 28.1, 28.2, 28.3, 28.4 4
KMPX 29 30 569 29.1 1
KWDA-LD 30 21 515
30.1, 30.2, 30.3, 30.4, 30.5, 30.6,.30.7,.30.8, 30.9 9
K31GL-LD 31 31 57531.1, 31.2, 31.3, 31.4, 31.5 5
KDAF 33 32 581 33.1, 33.2, 33.3 3
KJJM-LD 34 34 59334.1, 34.2, 34.3, 34.4, 34.5 5
KXTX 39 40 629 39.1, 39.2 2
KLEG-CD 44 44 653 44.1, 44.2, 44.3, 44.4 4
KTXD 47 46 66547.1, 47.2, 47.3, 47.4, 47.5 5
KST 49 48 677 49.1, 49.2, 49.3 3
KATA-CD 50 50 689 50.1, 50.2, 50.3, 50.4 4
KHFD-LD 51 51 69551.1, 51.2, 51.3, 51.4, 51.5, 51.6, 51.7, 51.8 8
KFWD 52 9 189 52.1 1
KAZD 55 39 62355.1, 55.2, 55.3, 55.4, 55.5, 55.6, 55.7 7
KDTX 58 45 65958.1, 58.2, 58.3, 58.4, 58.5 5
KPXD 68 42 641
68.1, 68.2, 68.3, 68.4, (68.11-68.21 encrypted) 4
Chan. 17 – Dielectric TFU-20EBT47 ft long, 10,600 lbs
Transmission Details• ERP – 1,000 KW• Antenna Gain – 17.5 (12.43 dB) – Omnidirectional• Antenna Input Power – 57.14 kW• Transmission Line – 1,500 ft of 8-3/16” rigid coax
• Loss in the transmission line – 1.21 dB – 18.35 kW (75.7% efficiency)• Transmitter Power Output – 75.49 kW• Would require a three IOT transmitter, each IOT at 30 kW rating, water cooled• The IOT operates at about 25 kVDC, 3 amps• Transmitter efficiency in the 30% range• New solid state transmitters achieve >60% efficiency. 50 VDC, water cooled.
WFAA History• WFAA Radio (AM) signed on June, 1922 (Working For All Alike)• Moved to 570 KC (not KHz back then) in 1938• Shared 570 and 820 with WBAP until 1970• WFAA-FM started October 1946. • WFAA-TV started as KBTV-TV in September, 1949 (Dumont network)• A. H. Belo purchased KBTV from oilman Tom Potter for $575K in March,
1950 and changed the call letters to WFAA-TV.• First VHF DTV station in the nation, and first DTV station in Texas –
February 27, 1998• Analog shut-down June 12, 2009• 2013, Belo sold all TV stations to Gannett. 2015, Gannett Broadcast
changed its name to TEGNA.
January 4, 1987
Thanks for inviting me!
