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Links
Published in Skip Pizzi, Graham A. Jones, A Broadcast Engineering Tutorial for Non-Engineers, 2014
Microwave links can carry both analog and digital audio and video signals. ENG links for DTV are available using COFDM modulation (see Chapter 4) to provide a very robust signal. Although such links must be licensed to broadcasters, this does not in itself ensure interference-free operation, since several broadcasters may be licensed to use the same frequency in a given area. Therefore, there must be good coordination between all operators of ENG microwave equipment in a given geographical area so their microwave links do not interfere with one other. This process is called frequency coordination, and in the U.S. it is often provided by local members of the Society of Broadcast Engineers (SBE). It becomes particularly crucial when a location becomes the center of a national event or news story, and multiple broadcasters from the local area and elsewhere converge on a single site, each seeking spectrum for their contribution links back to their studios or production centers.
Satellites
Published in Mohammad Razani, Commercial Space Technologies and Applications, 2018
Frequency band allocation to communication satellites is a very complex and detailed process that takes place at ITU for global allocations and at the country’s or region’s organization that is so assigned to this task such as Federal Communications Commission (FCC) in USA. According to ITU, the world is divided into three radio regions as showed in the following figure. The frequency coordination is carried out globally in the WARC or regionally in the regional administrative radio conferences (RARC).
Study on Work Roll Vertical Vibration Under Periodic Spalling of the Oxide Film
Published in Tribology Transactions, 2022
Jinxing Cui, Yan Peng, Jin Wang, Dakun Hu
The rolling interface instability is induced by the periodic change of the friction coefficient, for which a low-frequency self-excited vibration of the system can easily occur, resulting in the rolling instability problem induced by resonance (8–10, 13, 18). As for the rolling force on the roll in the process of heavy load deformation, the load change caused by the change of friction coefficient is very small. In this study, a multiscale small-parameter perturbation method is used to analyze the preceding nonlinear dynamic equations (33). Suppose that where is the frequency coordination factor and is a small parameter. The system is regarded as an autonomous nonlinear system, and Eq. [16] can be written as The equation with a small-scale parameter can be written (33) The solution of Eq. [17] can be written as