Helical scan

Helical scan
Helical recording method
Media typemagnetic tape
Usagerecording high-frequency signals

Helical scan is a method of recording high-frequency signals on magnetic tape, used in open-reel video tape recorders, video cassette recorders, digital audio tape recorders, and some computer tape drives.

With this technique, magnetic tape heads (or head chips) are placed on a rotating head drum.[1] which run the chips at high speed (or angular velocity). The tape is wrapped tightly around the drum. Either the drum[2] and/or the tape is tilted at an angle that allows the head chips to read the tape diagonally faster, so the linear speed of the tape may be slower than the speed of the head chips, which rotate at a higher speed allowing signals to be transmitted. high frequency, such as video, are recorded.[3][4][5] The diagonal tracks read or written using this method are known as helical tracks.[2]

The head drum of a Hi-Fi NTSC VHS VCR; three of the six heads face the reader. The helical path of the tape around the drum can clearly be seen.
The same head drum with the rotating portion elevated for clarity
The rotating portion of the head drum showing the rotary transformer and three of the six tape heads used in this particular VCR
  1. ^ "Rotary magnetic head drum with fluid bearing and with head chips mounted together in parallel".
  2. ^ a b Tozer, E. P. J. (November 12, 2012). Broadcast Engineer's Reference Book. CRC Press. ISBN 9781136024184 – via Google Books.
  3. ^ Capelo, Gregory; Brenner, Robert C. (June 26, 1998). VCR Troubleshooting and Repair. Newnes. ISBN 9780750699402 – via Google Books.
  4. ^ Daniel, Eric D.; Mee, C. Denis; Clark, Mark H. (August 31, 1998). Magnetic Recording: The First 100 Years. John Wiley & Sons. ISBN 9780780347090 – via Google Books.
  5. ^ Information, Reed Business (December 1, 1983). "New Scientist". Reed Business Information – via Google Books. {{cite web}}: |first= has generic name (help)

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