Probe – WDST FM Example
In the example below we show Longley-Rice and FCC method coverage of WDST, an FM radio station licensed in upstate New York. The map provides a good comparison between the two coverage prediction methods.
In the map below we have predicted the Longley-Rice signal and the FCC signal out to the 40 dBu signal level. However, since this station is protected basically to its 60 dBu coverage contour, it is likely that interference will be received beyond the 60 dBu that will influence coverage. The coverage depicted on this map and the one above are mapped using gradient shading, where one color blends to another depending on the strength of the signal at any given location.
In the example below we show the conventional FCC F(50-50) 40,50 and 60 dBu contours. We also list the stations that may interfere with the desired signal within those coverage contours. Just a glance can show you that there is a difference between the predicted coverage and predicted interference-free coverage. Note that in this study the desired WDST signal was compared with the undesired signals within a 100 km circle around the transmitter. Areas where the predicted undesired signal was higher than the U/D ratio permitted by the FCC for the frequency relationship involved are colored. Each color represents a location where a given undesired transmitter signal is greater than it should be for WDST to be interference free.
Below you will find the tabulated population report for the map study shown above. The report lists the housing units, population and area where interference may be defined to be caused. Also, the report details the masking provided by other stations over the interference areas. “Unique interference” is that caused by a station that is not masked by interference from another station. Similar methodology is employed for doing television interference analysis using the FCC’s OET-69 criteria.
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WDST (261) Woodstock, NY FM Interference Study Interference considered within 100.0 km from the reference transmitter and within 100.0 km from each possible interferer Signal Resolution: 2 km Study Date: 2/7/2002 FM Database Date: 02-07-02 D/U Ratios Used: Co: 20.0 dB First Adj: 6.0 dB Second Adj: -40.0 dB Third Adj: -40.0 dB Population Database: US Census Percentages calculated using a baseline population of 1,395,498. Stations which cause interference: Call Letters H Units Population % Area (sq. km) WEZNFM (260) 110914 297567 21.323 2647.01 WRCH (263) 8861 23303 1.670 233.53 WCATFM (260) 2680 5593 0.401 162.92 WWFX (261) 889 1176 0.084 83.41 WMNB (261) 212063 496426 35.573 3220.10 WHTZ (262) 99196 275054 19.710 1618.13 WRVE (258) 173426 409059 29.313 1217.04 WBAI (258) 9176 23872 1.711 73.61 WJUX (259) 8852 14917 1.069 438.13 WDHI (262) 31500 62794 4.500 1083.59 WKBE (262) 173624 411088 29.458 1050.23 WHUD (264) 48256 133202 9.545 682.71 WODEFM (260) 4272 10467 0.750 209.25 WQFN (261) 29099 66092 4.736 1435.67 Masking Summary: Total Interference Unique Interference Call Letters Population % Population % WEZNFM (260) 297567 21.323 69304 4.966 WRCH (263) 23303 1.670 0 0.000 WCATFM (260) 5593 0.401 0 0.000 WWFX (261) 1176 0.084 34 0.002 WMNB (261) 496426 35.573 61913 4.437 WHTZ (262) 275054 19.710 38066 2.728 WRVE (258) 409059 29.313 271 0.019 WBAI (258) 23872 1.711 0 0.000 WJUX (259) 14917 1.069 201 0.014 WDHI (262) 62794 4.500 6231 0.447 WKBE (262) 411088 29.458 4 0.000 WHUD (264) 133202 9.545 1147 0.082 WODEFM (260) 10467 0.750 0 0.000 WQFN (261) 66092 4.736 11474 0.822 Stations considered which do not cause interference: WBGK (259) WIII (260) WBGJ (262) WCDW (263) WKVU (264) WUSR (258) WLEV (264) WVAY (264) ------------------------------------------------------------------------ Call Letters City State Dist Bear WEZNFM (260) Bridgeport CT 105.1 138.4 WRCH (263) New Britain CT 103.5 107.5 WCATFM (260) Athol MA 164.3 65.3 WWFX (261) Southbridge MA 178.7 80.9 WMNB (261) North Adams MA 111.2 44.7 WHTZ (262) Newark NJ 137.9 178.9 WRVE (258) Schenectady NY 71.9 1.5 WBAI (258) New York NY 137.9 178.9 WJUX (259) Monticello NY 63.7 245.8 WBGK (259) Newport Village NY 152.5 327.3 WIII (260) Cortland NY 187.1 290.4 WDHI (262) Delhi NY 80.4 302.7 WBGJ (262) Sylvan Beach NY 199.8 315.5 WKBE (262) Warrensburg NY 160.2 7.5 WCDW (263) Conklin NY 139.6 273.4 WHUD (264) Peekskill NY 73.1 171.8 WKVU (264) Utica NY 151.3 320.7 WUSR (258) Scranton PA 154.8 247.1 WODEFM (260) Easton PA 174.1 215.6 WQFN (261) Forest City PA 125.5 249.9 WLEV (264) Allentown PA 198.1 217.4 WVAY (264) Wilmington VT 140.4 39.6 ------------------------------------------------------------------------ Totals for WDST (261) Calculation Area Population: 2,933,868 ( 31425.3 sq. km ) Not Affected by Terrain Loss: 1,395,498 ( 14461.6 sq. km ) Interfered Population: 904,333 ( 7960.8 sq. km ) Interference Free: 491,165 ( 6500.7 sq. km ) Percent Interference: 64.80 Terrain Blocked Population: 1,538,370 ( 16963.7 sq. km)