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E2B10

OPERATING PROCEDURES · Television practices: fast-scan television standards and techniques; slow scan television standards and techniques

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What aspect of an analog slow-scan television signal encodes the brightness of the picture?

  1. ATone frequency
  2. BTone amplitude
  3. CSync amplitude
  4. DSync frequency
Why Analog SSTV is an audio-frequency FM-style mode: each pixel's luminance is sent as a tone whose frequency varies between about 1500 Hz for black and 2300 Hz for white, with sync pulses at 1200 Hz. Because the information is in the frequency, the signal can be fed straight into an SSB transmitter and survives fading and level changes on the path. The receiving software measures the instantaneous tone frequency to rebuild each line of the picture.
Watch out Tone amplitude sounds plausible because brighter usually means stronger, but amplitude varies with propagation and audio gain, so it would make the picture brightness depend on band conditions; amplitude carries no picture data in SSTV.
SSTV is FM by ear: 1200 Hz sync, 1500 Hz black, 2300 Hz white. Higher pitch equals brighter pixel.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E2B

  1. E2B01 In digital television, what does a coding rate of 3/4 mean?
  2. E2B02 How many horizontal lines make up a fast-scan (NTSC) television frame?
  3. E2B03 How is an interlaced scanning pattern generated in a fast-scan (NTSC) television system?
  4. E2B04 How is color information sent in analog SSTV?
  5. E2B05 Which of the following describes the use of vestigial sideband in analog fast-scan TV transmissions?
  6. E2B06 What is vestigial sideband modulation?
  7. E2B07 Which types of modulation are used for amateur television DVB-T signals?
  8. E2B08 What technique allows commercial analog TV receivers to be used for fast-scan TV operations on the 70-centime…
  9. E2B09 What kind of receiver can be used to receive and decode SSTV using the Digital Radio Mondiale (DRM) protocol?
  10. E2B10 What aspect of an analog slow-scan television signal encodes the brightness of the picture?
  11. E2B11 What is the function of the vertical interval signaling (VIS) code sent as part of an SSTV transmission?
  12. E2B12 What signals SSTV receiving software to begin a new picture line?
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