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T8A10

SIGNALS AND EMISSIONS · Basic characteristics of FM and SSB; Bandwidth of various modulation modes: CW, SSB, FM, fast-scan TV; Choice of emission type: selection of USB vs LSB, use of SSB for weak signal work, use of FM for VHF packet and repeaters

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What is the approximate bandwidth of AM fast-scan TV transmissions?

  1. AMore than 10 MHz
  2. BAbout 6 MHz
  3. CAbout 3 MHz
  4. DAbout 1 MHz
Why Amateur fast-scan TV uses the same analog NTSC format as old broadcast television, so it occupies a standard 6 MHz channel: a vestigial-sideband video carrier plus a separate FM audio subcarrier about 4.5 MHz above it. That much bandwidth will not fit in any HF or VHF band segment, which is why fast-scan TV is used on 70 cm and higher. For comparison, FM voice is about 10-15 kHz and SSB voice about 3 kHz, so TV is hundreds of times wider.
Watch out The choice of about 3 MHz is roughly the video portion alone if you forget the guard space and sound subcarrier; more than 10 MHz is wider than any allocated broadcast TV channel.
ATV = a broadcast TV channel = 6 MHz, so it only fits on 70 cm and up.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of T8A

  1. T8A01 Which of the following is a form of amplitude modulation?
  2. T8A02 What type of modulation is commonly used for VHF packet radio transmissions?
  3. T8A03 Which type of voice mode is often used for long-distance (weak signal) contacts on the VHF and UHF bands?
  4. T8A04 Which type of modulation is commonly used for VHF and UHF voice repeaters?
  5. T8A05 Which of the following signal types has the narrowest bandwidth?
  6. T8A06 Which sideband is normally used for 10-meter HF, VHF, and UHF single-sideband communications?
  7. T8A07 What is one characteristic of single sideband (SSB) compared to FM?
  8. T8A08 What is the approximate bandwidth of a typical single sideband (SSB) voice signal?
  9. T8A09 What is the approximate bandwidth of an FM voice signal on VHF repeaters?
  10. T8A10 What is the approximate bandwidth of AM fast-scan TV transmissions?
  11. T8A11 What is the approximate bandwidth required to transmit a CW signal?
  12. T8A12 Which of the following is a disadvantage of FM compared with single sideband?
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