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| adjacent-channel_interference [2023/09/20 18:52] – RabbitEars Webmaster | adjacent-channel_interference [2023/09/20 19:02] (current) – RabbitEars Webmaster |
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| In any event, when the FCC is trying to determine whether or not a station is allowed to exist on an adjacent channel, it does this analysis across a geographic area using the methodology in OET Bulletin No. 69, using the TVStudy software. The FCC breaks the coverage area of the impacted station into a grid, and each cell of the grid has a representative point where a calculation is done of the signals in question. If the undesired signal exceeds the threshold with respect to the desired signal, that cell is flagged as having interference. | In any event, when the FCC is trying to determine whether or not a station is allowed to exist on an adjacent channel, it does this analysis across a geographic area using the methodology in OET Bulletin No. 69, using the TVStudy software. The FCC breaks the coverage area of the impacted station into a grid, and each cell of the grid has a representative point where a calculation is done of the signals in question. If the undesired signal exceeds the threshold with respect to the desired signal, that cell is flagged as having interference. |
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| Above is a map I made back in 2018, which you can click to expand to its full size. I used unusual options in TVStudy to create a highly-detailed map, so while the FCC only permits a cell size down to 0.5 km on a side, I used 0.1 km on a side. The desired station here is WNCN on channel 8. The purple areas are those where WNCN is predicted to receive interference. You can see a pretty distinct interference area just south of Goldsboro; these are cells impacted specifically by adjacent-channel interference from WHFL-CD on channel 7. | Above is a map from 2018, which you can click to expand to its full size. Unusual options were used in TVStudy to create a highly-detailed map, so while the FCC only permits a cell size down to 0.5 km on a side, this map uses 0.1 km on a side. The desired station here is WNCN on channel 8. The purple areas are those where WNCN is predicted to receive interference. You can see a pretty distinct interference area just south of Goldsboro; these are cells impacted specifically by adjacent-channel interference from WHFL-CD on channel 7. |
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| Once the analysis of each cell is complete, the population of the flagged cells is added together and divided by the total prior interference-free population. If the impacted station is a full-service or Class A station, then that number cannot exceed 0.5%. If it's an LPTV or translator, it cannot exceed 2%. Stations can negotiate and sign an interference agreement to accept interference in excess of those values, but they can also opt not to negotiate and those FCC-set limits hold. | Once the analysis of each cell is complete, the population of the flagged cells is added together and divided by the total prior interference-free population. If the impacted station is a full-service or Class A station, then that number cannot exceed 0.5%. If it's an LPTV or translator, it cannot exceed 2%. Stations can negotiate and sign an interference agreement to accept interference in excess of those values, but they can also opt not to negotiate and those FCC-set limits hold. |
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