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    Sam Drazin
    Methods of avoiding TV stations when coordinating freqs
    Topic posted November 15, 2011 by Sam DrazinExpert, last edited November 26, 2013 by AdminProficient, tagged how-to 
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    Title:
    Methods of avoiding TV stations when coordinating freqs
    Description:

    Overview

    TV stations make up yet another series of obstacles to work around when coordinating frequencies. Depending on your geographic location, you may be heavily impacted by the transmission of one or more TV stations. This page will briefly discuss several methods of avoiding TV stations when performing Frequency Coordination.

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    Avoiding TV Channels

    To avoid active TV channels in your vicinity, you might use any of the methods explained in the Creating Exclusions page to block off certain portions of the spectrum from use. In general, however, the most accurate depiction of your RF environment will be captured by running a live scan, and generating exclusions based off of that data.

    The TV database is a static file which calculates your proximity from local TV stations, and blocks out entire TV channels if they are close enough to present an issue. Using the TV Exclusions approach is often overly conservative, as many TV stations are very low power, or blocked by natural/man-made obstructions (mountain ranges, tall buildings, etc) such that they would not present any material interference.

    For this reason, it is recommended to always perform a live scan with a wide-band antenna system placed to optimally cover your area of wireless usage.

    Using the TV Exclusions database is an acceptable fallback plan if accurate scans cannot be taken of the RF environment in whcih you plan to operate your wireless equipment. When scanning is an option, however, there is no need to use TV exclusions. Scan data taken recently from the precise environment in which your gear will operate is the most accurate source of the present RF environment (assuming your hardware and antenna rig is functional and well-tuned).

    This being said, scan data is, by definition, time-dependent. You might take a scan of a venue and see no strong signals, and an hour later, become inundated with broadcast and ENG wireless systems and 2-way intercom communication that clutters your once-clear spectrum. To address this concern, use of the Frequency Plot should be made to constantly scan the spectrum.

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