World Library  
Flag as Inappropriate
Email this Article

Residual carrier

Article Id: WHEBN0024970806
Reproduction Date:

Title: Residual carrier  
Author: World Heritage Encyclopedia
Language: English
Subject: White clipper, Output power of an analog TV transmitter, PAL-S, Distortionmeter, Television lines
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Residual carrier

In analogue TV technology, residual carrier is the ratio of carrier level which is modulated by the maximum video signal to the unmodulated carrier level.

Video signal

Video signal (VF) or more formally composite video signal (CVS) is the signal which carries the video information as well as some auxiliary signals for synchronizing. In all systems 0-300 mV level is reserved for auxiliary signals and 300-1000 mV is reserved for video information. In monochrome TV, 300 mV (or sometimes 350 mV) corresponds to black and 1000 mV corresponds to white.( In color TV depending on the system used, superimposed color subcarrier may have slightly higher values. )

Modulation

The signal modulates a carrier by amplitude modulation, where an increase in the video modulating signal produces a decrease in the carrier amplitude, called "negative modulation". When there is no modulating signal, the carrier has the full level and when there is a modulating video frequency (VF) signal the level of IF is lower. Since the level when transmitting a black scene is lower than the white level, the level of carrier when transmitting black is higher than the level of carrier when transmitting white.

Carrier modulated by 1 Volt VF. (1 volt corresponds to white.) In this illustration, the carrier frequency is much lower than would practically be used, relative to the video signal frequency.

The modulators are set[1] to yield 10% or 12.5% of carrier level when modulated by 1 V signal (which corresponds to white scene) This percentage is known as residual carrier.

An example of the modulated carrier is shown in the accompanying figure. In this figure, the level of the modulating VF signal is 1 volt (white level). 1 V. yields residual carrier (10%) . Short duration full carrier (100%) is the sync pulse and the 73% is so called back porch (black level). The duration of the signal is approximately 100 ┬Ás.

See also

References and notes

  1. ^ Broadcast Engineers'Handbook
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.