page_title: Amateur television
section_title: Transmission characteristics
hierarchical_section_title: Amateur television / Transmission characteristics
caption_attribution_description: English: A simulation of severe phase errors in PAL color decoding shown applied to a PM5544 test pattern. In this example the chroma delay line has been disabled, making the phase errors cause Hanover bars. The outermost columns of the test pattern contain color signals that do not alternate phase between lines unlike a normal PAL signal; if the phase is correct those signals will have complementary color from line to line, and cancel out if a delay line is present.
context_page_description: Amateur television is the transmission of broadcast quality video and audio over the wide range of frequencies of radio waves allocated for radio amateur use. ATV is used for non-commercial experimentation, pleasure, and public service events. Ham TV stations were on the air in many cities before commercial television stations came on the air. Various transmission standards are used, these include the broadcast transmission standards of NTSC in North America and Japan, and PAL or SECAM elsewhere, utilizing the full refresh rates of those standards. ATV includes the study of building of such transmitters and receivers, and the study of radio propagation of signals travelling between transmitting and receiving stations.
  ATV is an extension of amateur radio. It is also called HAM TV or fast-scan TV, as opposed to slow-scan television.
context_section_description: Typically frequency modulated TV is used on frequencies above 1,240 MHz (1.24 GHz), where there is enough bandwidth for such wideband transmissions. This is often used as a repeater's input frequency, with output being standard VSB on the four channels listed above.
  In a nutshell
  below 1.24 GHz: Vestigial Sideband
  above 1.24 GHz: FM, PSK etc...
  The quality of transmission is expressed as a "p level"; "p" standing for "picture". P levels range from zero to five, increasing as the picture becomes more viewable. P-0 signifies a state in which sync bars are visible, but the picture is too snowy to be seen; this occurs at a minimum signal strength of 3 dB. Each level represents an increase of 6 dB over the previous; P-5 is 30 dB above P-0 and represents a perfectly clear picture.
caption: Typical fast scan test card showing "Hanover bars" (colour banding) effect in Pal S (simple) signal mode of transmission.
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