Editing Heterodyne (section)

===Analog videotape recording===
<!-- [[Color under]] redirects here. Please fix it if the name of this section changes :) -->
Many analog [[videotape]] systems rely on a downconverted color subcarrier to record color information in their limited bandwidth. These systems are referred to as "heterodyne systems" or "color-under systems". For instance, for [[NTSC]] video systems, the [[VHS]] (and [[S-VHS]]) recording system converts the color subcarrier from the NTSC standard 3.58&nbsp;MHz to ~629&nbsp;kHz.<ref name = lionlamb>[http://www.lionlmb.org/quad/format.html#12incomposite Videotape formats using {{convert|1/2|in|mm|adj=mid|-wide}} tape] {{Webarchive|url=https://web.archive.org/web/20060616104342/http://lionlmb.org/quad/format.html#12incomposite |date=June 16, 2006 }} ; Retrieved 2007-01-01</ref> [[PAL]] VHS color subcarrier is similarly downconverted (but from 4.43&nbsp;MHz). The now-obsolete 3/4" [[U-matic]] systems use a heterodyned ~688&nbsp;kHz subcarrier for NTSC recordings (as does [[Sony]]'s [[Betamax]], which is at its basis a 1/2″ consumer version of U-matic), while PAL U-matic decks came in two mutually incompatible varieties, with different subcarrier frequencies, known as Hi-Band and Low-Band. Other videotape formats with heterodyne color systems include [[Video-8]] and [[Hi8]].<ref name = poynton>{{cite book|first=Poynton |last=Charles |author-link=Charles Poynton |title=Digital Video and HDTV: Algorithms and Interfaces |year=2003 |publisher=Morgan Kaufmann Publishers |location=San Francisco |pages=582–3 |isbn=978-1-55860-792-7 |url=https://books.google.com/books?id=ra1lcAwgvq4C}}</ref>

The heterodyne system in these cases is used to convert quadrature phase-encoded and amplitude modulated sine waves from the broadcast frequencies to frequencies recordable in less than 1&nbsp;MHz bandwidth. On playback, the recorded color information is heterodyned back to the standard subcarrier frequencies for display on televisions and for interchange with other standard video equipment.

Some U-matic (3/4″) decks feature 7-pin mini-[[DIN connector]]s to allow dubbing of tapes without conversion, as do some industrial VHS, S-VHS, and Hi8 recorders.