A fast-scan (NTSC) frame has 525 lines. To cut flicker it is sent as two fields: the first scans the odd-numbered lines, the second fills in the even-numbered lines. About 60 fields make 30 frames each second.
Drawn with 15 lines instead of 525. Same pattern.
Remember525 lines per frame. Interlace = odd lines, then even lines.
Vestigial sideband trims AM without losing the low video frequencies
Vestigial sideband is AM in which one complete sideband and a portion of the other are sent. That cuts bandwidth, while the low video frequencies near the carrier stay intact on both sides.
Video signal frequency runs outward from the carrier. VSB trims the lower sideband's far side.
Analog fast-scan on 70 cm works with ordinary TVs because the band overlaps channels shared with cable TV: a cable-ready set tunes it directly.
RememberVSB = one full sideband plus a stub of the other.
Coding rate is the data share. QPSK and QAM carry the bits.
Digital ATV adds forward error correction (FEC) bits so the receiver can repair errors. A coding rate of 3/4 means 3 of every 4 bits are data and 25% is FEC. DVB-T amateur TV is modulated with QPSK or QAM.
Coding rate = data bits out of all bits. Modulation = bits per symbol.
Remember3/4 = three data bits per one error-correction bit (25% FEC).
SSTV paints a picture with audio tones: pitch is brightness
Analog slow-scan TV is sent as audio tones, so an SSB radio can carry it. Tone frequency = brightness. Specific tones tell the software a new line starts. Color lines go one after another. The VIS code at the start identifies the SSTV mode.
Frequency, not amplitude, carries brightness. Specific tones mark the line start.
Digital SSTV in the DRM protocol is also an audio signal, so an SSB receiver can receive and decode it.
RememberPitch = brightness. Sync tone = new line. VIS = which mode.