A radio path occupies an ellipsoidal region called a Fresnel zone,
not just the optical line between antennas. Objects inside the Fresnel zone can
cause diffraction loss and multipath fading.
Fresnel radius is calculated from r = √( λ d1d2
/ (d1 + d2) ), where λ is wavelength, d1
is distance from Antenna #1, and d2 is distance from Antenna #2.
The plot uses a chord between the two antenna-site ground points. Earth curvature
is drawn above that chord. Antennas and obstruction are drawn upward from the curved
Earth surface. The Fresnel boundaries are the LOS path plus and minus the selected
Fresnel-zone radius.
Disclaimer: These calculations are believed to be accurate, but you must validate
all results for critical applications. RF Cafe's calculators are entirely unique
code - not "borrowed" from somebody else's work.
Wavelength
0.124914 m / 0.4098 ft
Obstruction distance from Antenna #2
80.0000 mi
Earth center chord height
1667.065 ft
Chord angle
1.447229°
LOS height at obstruction
633.083 ft AGL
FZ1 at obstruction
Upper: 819.152, Lower: 447.014 ft AGL, Lower clearance: -302.986 ft
FZ2 at obstruction
Upper: 744.725, Lower: 521.442 ft AGL, Lower clearance: -228.558 ft
Dist. from Ant. #1 (mi)
Earth Bulge (ft)
LOS AGL (ft)
FZ1 Radius (ft)
FZ1 Upper AGL (ft)
FZ1 Lower AGL (ft)
FZ1 Lower Above Obs. (ft)
FZ2 Radius (ft)
FZ2 Upper AGL (ft)
FZ2 Lower AGL (ft)
FZ2 Lower Above Obs. (ft)
0.0000
0.000
1500.000
0.000
1500.000
1500.000
750.000
0.000
1500.000
1500.000
750.000
2.0000
130.696
1389.304
65.124
1454.428
1324.179
574.179
39.075
1428.378
1350.229
600.229
4.0000
256.058
1283.942
91.155
1375.096
1192.787
442.787
54.693
1338.635
1229.249
479.249
6.0000
376.086
1183.914
110.472
1294.386
1073.442
323.442
66.283
1250.197
1117.630
367.630
8.0000
490.779
1089.221
126.198
1215.419
963.022
213.022
75.719
1164.939
1013.502
263.502
10.0000
600.138
999.862
139.552
1139.413
860.310
110.310
83.731
1083.593
916.130
166.130
12.0000
704.163
915.837
151.163
1067.000
764.674
14.674
90.698
1006.535
825.139
75.139
14.0000
802.853
837.147
161.409
998.556
675.738
-74.262
96.845
933.992
740.301
-9.699
16.0000
896.209
763.791
170.535
934.326
593.256
-156.744
102.321
866.112
661.470
-88.530
18.0000
984.230
695.770
178.714
874.483
517.056
-232.944
107.228
802.998
588.542
-161.458
20.0000 *
1066.917
633.083
186.069
819.152
447.014
-302.986
111.641
744.725
521.442
-228.558
22.0000
1144.269
575.731
192.696
768.427
383.035
-366.965
115.618
691.349
460.113
-289.887
24.0000
1216.287
523.713
198.667
722.381
325.046
-424.954
119.200
642.914
404.513
-345.487
26.0000
1282.970
477.030
204.041
681.071
272.990
-477.010
122.424
599.455
354.606
-395.394
28.0000
1344.318
435.682
208.862
644.544
226.820
-523.180
125.317
560.999
310.365
-439.635
30.0000
1400.332
399.668
213.169
612.837
186.499
-563.501
127.901
527.569
271.767
-478.233
32.0000
1451.011
368.989
216.992
585.981
151.997
-598.003
130.195
499.184
238.794
-511.206
34.0000
1496.356
343.644
220.356
564.000
123.288
-626.712
132.214
475.858
211.430
-538.570
36.0000
1536.366
323.634
223.283
546.917
100.351
-649.649
133.970
457.604
189.664
-560.336
38.0000
1571.041
308.959
225.789
534.747
83.170
-666.830
135.473
444.432
173.486
-576.514
40.0000
1600.382
299.618
227.887
527.505
71.731
-678.269
136.732
436.350
162.886
-587.114
42.0000
1624.388
295.612
229.590
525.202
66.022
-683.978
137.754
433.366
157.858
-592.142
44.0000
1643.059
296.941
230.906
527.846
66.035
-683.965
138.543
435.484
158.397
-591.603
46.0000
1656.396
303.604
231.841
535.445
71.763
-678.237
139.105
442.708
164.499
-585.501
48.0000
1664.398
315.602
232.400
548.002
83.202
-666.798
139.440
455.042
176.162
-573.838
50.0000
1667.065
332.935
232.586
565.521
100.348
-649.652
139.552
472.486
193.383
-556.617
52.0000
1664.398
355.602
232.400
588.002
123.202
-626.798
139.440
495.042
216.162
-533.838
54.0000
1656.396
383.604
231.841
615.445
151.763
-598.237
139.105
522.708
244.499
-505.501
56.0000
1643.059
416.941
230.906
647.846
186.035
-563.965
138.543
555.484
278.397
-471.603
58.0000
1624.388
455.612
229.590
685.202
226.022
-523.978
137.754
593.366
317.858
-432.142
60.0000
1600.382
499.618
227.887
727.505
271.731
-478.269
136.732
636.350
362.886
-387.114
62.0000
1571.041
548.959
225.789
774.747
323.170
-426.830
135.473
684.432
413.486
-336.514
64.0000
1536.366
603.634
223.283
826.917
380.351
-369.649
133.970
737.604
469.664
-280.336
66.0000
1496.356
663.644
220.356
884.000
443.288
-306.712
132.214
795.858
531.430
-218.570
68.0000
1451.011
728.989
216.992
945.981
511.997
-238.003
130.195
859.184
598.794
-151.206
70.0000
1400.332
799.668
213.169
1012.837
586.499
-163.501
127.901
927.569
671.767
-78.233
72.0000
1344.318
875.682
208.862
1084.544
666.820
-83.180
125.317
1000.999
750.365
0.365
74.0000
1282.970
957.030
204.041
1161.071
752.990
2.990
122.424
1079.455
834.606
84.606
76.0000
1216.287
1043.713
198.667
1242.381
845.046
95.046
119.200
1162.914
924.513
174.513
78.0000
1144.269
1135.731
192.696
1328.427
943.035
193.035
115.618
1251.349
1020.113
270.113
80.0000
1066.917
1233.083
186.069
1419.152
1047.014
297.014
111.641
1344.725
1121.442
371.442
82.0000
984.230
1335.770
178.714
1514.483
1157.056
407.056
107.228
1442.998
1228.542
478.542
84.0000
896.209
1443.791
170.535
1614.326
1273.256
523.256
102.321
1546.112
1341.470
591.470
86.0000
802.853
1557.147
161.409
1718.556
1395.738
645.738
96.845
1653.992
1460.301
710.301
88.0000
704.163
1675.837
151.163
1827.000
1524.674
774.674
90.698
1766.535
1585.139
835.139
90.0000
600.138
1799.862
139.552
1939.413
1660.310
910.310
83.731
1883.593
1716.130
966.130
92.0000
490.779
1929.221
126.198
2055.419
1803.022
1053.022
75.719
2004.939
1853.502
1103.502
94.0000
376.086
2063.914
110.472
2174.386
1953.442
1203.442
66.283
2130.197
1997.630
1247.630
96.0000
256.058
2203.942
91.155
2295.096
2112.787
1362.787
54.693
2258.635
2149.249
1399.249
98.0000
130.696
2349.304
65.124
2414.428
2284.179
1534.179
39.075
2388.378
2310.229
1560.229
100.0000
0.000
2500.000
0.000
2500.000
2500.000
1750.000
0.000
2500.000
2500.000
1750.000
* Row at entered obstruction distance. “Above Obs.” compares the lower Fresnel boundary with the entered obstruction AGL height.
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in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide
me with ready access to commonly needed formulas and reference material while performing
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