Some Commonly Asked Questions
                      About EMC Measurement Units:

Units:

          E or V = Volts  (can use either, as per convention standards)
          R = Ohms (impedence/resitance)
          P = Power (Watts, dBm, mW, or W)
          dB = decibel ratio (log10) - all log's will be to base 10
          W = Watts = (E.E)/R
          u = micro = 10E-6 (for all units - E, R, P, or V)
          m = milli = 10E-3 (for all units - E, R, P, or V)
          dBm = decibel ratio of Watts  W to one milliwatt
                   = 10log10 (W/mW)
          dBuV = decibel ratio of Volts to one microvolt
                   = 20log10 {V/uV} or, for example, {E/uV}

Conversions for  50 ohm systems:

    1. To convert dBm  to dBuV add 107 dB:         dBuV = dBm + 107 dB
    2. To conver dBuV to dBm subtract 107 dB:     dBm = dBuV - 107 dB

Proof:
                 Remember, 0 dBm = 1 mW (milliwatt) = 0.001 Watts

        1.0         E = Square Root of (W x R) - assume R = 50 Ohms
                    Note: for dBm our reference will be  1 mW
        2.0         E  = Square Root (1mW* x  50 ohms) = 0.224 Volts
        3.0         dBuV = 20 log10 (0.224 Volts/1uV*) = 107 dBuV
        4.0          Therefore, 107 dBuV = 0 dBm in a 50 W system
        5.0         Using this as the scale factor:  dBm + 107 dB = dBuV
                                  *  Must be entered in Watts (0.001 or 1x10-3 W = 1 mW)
                                  * Must be entered in Volts (0.000001 or 1x10E-6 V = 1uV)
 
Caution:

One common mistake observed in using conversions is in summing or subtracting  powers.
Powers (Watts) can be added, voltages and log10 values cannot be added or subtracted.

As an example, in  case of a  50 Ohm system:

                        5 mW  =  7  dBm  = 114  dBuV  =  501.2 mV
                +      8 mW  =  9  dBm  = 116  dBuV  =  631.0 mV
                      13 mW  = 11 dBm  = 118  dBuV  =  794.3 mV

Where,  uV  stands  for  micro  Volts
          mV  stands  for  milli  Volts
 
Radiated Measurement Units:

                        uV/m = microvolts per meter = Field Strength
                        dBuV/m = decibel ratio referenced to a microvolt per meter = Field Strength
                        AF = Antenna Factor = losses associated with the receive antenna
                        CL = Cable Loss = signal loss within the transmission line/cable

    Field strength measurements are normally measured and calculated as follows:
          FS(dBuV/m) = Indicated Signal Level(dBuV)+AF(dB)+CL(dB)

Field strengths in microvolts per meter (mV/m) can be calculated by taking the inverse log of the field strength measured in dBuV/m. As an example:
 
                         FS(uV/m) = 10 raised  to  the  power  of {(dBuV/m)/20}

    where,

 FS = Field Strength in decibels above a microvolt per meter or in microvolts per meter
 Indicated Signal Level = signal level observed on the receiver (spectrum analyzer)
                    Note: usually read in dBuV, or in dBm and converted to dBuV.
AF = Antenna Factor (signal loss) in dB
CL = Cable Loss (signal loss) in dB

Unit Equivalent Cross-reference for 50 Ohm Systems
Unit Equivalent Cross-reference for 50 Ohm Systems            
dBm dBw dBuV Vrms dBuA Arms W
-100 -130 6.9897 2.24E-06 -26.9897 4.47E-08 1E-13
-99 -129 7.9897 2.51E-06 -25.9897 5.02E-08 1.26E-13
-98 -128 8.9897 2.82E-06 -24.9897 5.63E-08 1.58E-13
-97 -127 9.9897 3.16E-06 -23.9897 6.32E-08 2E-13
-96 -126 10.9897 3.54E-06 -22.9897 7.09E-08 2.51E-13
-95 -125 11.9897 3.98E-06 -21.9897 7.95E-08 3.16E-13
-94 -124 12.9897 4.46E-06 -20.9897 8.92E-08 3.98E-13
-93 -123 13.9897 5.01E-06 -19.9897 1E-07 5.01E-13
-92 -122 14.9897 5.62E-06 -18.9897 1.12E-07 6.31E-13
-91 -121 15.9897 6.3E-06 -17.9897 1.26E-07 7.94E-13
-90 -120 16.9897 7.07E-06 -16.9897 1.41E-07 1E-12
-89 -119 17.9897 7.93E-06 -15.9897 1.59E-07 1.26E-12
-88 -118 18.9897 8.9E-06 -14.9897 1.78E-07 1.58E-12
-87 -117 19.9897 9.99E-06 -13.9897 2E-07 2E-12
-86 -116 20.9897 1.12E-05 -12.9897 2.24E-07 2.51E-12
-85 -115 21.9897 1.26E-05 -11.9897 2.51E-07 3.16E-12
-84 -114 22.9897 1.41E-05 -10.9897 2.82E-07 3.98E-12
-83 -113 23.9897 1.58E-05 -9.9897 3.17E-07 5.01E-12
-82 -112 24.9897 1.78E-05 -8.9897 3.55E-07 6.31E-12
-81 -111 25.9897 1.99E-05 -7.9897 3.99E-07 7.94E-12
-80 -110 26.9897 2.24E-05 -6.9897 4.47E-07 1E-11
-79 -109 27.9897 2.51E-05 -5.9897 5.02E-07 1.26E-11
-78 -108 28.9897 2.82E-05 -4.9897 5.63E-07 1.58E-11
-77 -107 29.9897 3.16E-05 -3.9897 6.32E-07 2E-11
-76 -106 30.9897 3.54E-05 -2.9897 7.09E-07 2.51E-11
-75 -105 31.9897 3.98E-05 -1.9897 7.95E-07 3.16E-11
-74 -104 32.9897 4.46E-05 -0.9897 8.92E-07 3.98E-11
-73 -103 33.9897 5.01E-05 0.0103 1E-06 5.01E-11
-72 -102 34.9897 5.62E-05 1.0103 1.12E-06 6.31E-11
-71 -101 35.9897 6.3E-05 2.0103 1.26E-06 7.94E-11
-70 -100 36.9897 7.07E-05 3.0103 1.41E-06 1E-10
-69 -99 37.9897 7.93E-05 4.0103 1.59E-06 1.26E-10
-68 -98 38.9897 8.9E-05 5.0103 1.78E-06 1.58E-10
-67 -97 39.9897 9.99E-05 6.0103 2E-06 2E-10
-66 -96 40.9897 0.000112 7.0103 2.24E-06 2.51E-10
-65 -95 41.9897 0.000126 8.0103 2.51E-06 3.16E-10
-64 -94 42.9897 0.000141 9.0103 2.82E-06 3.98E-10
-63 -93 43.9897 0.000158 10.0103 3.17E-06 5.01E-10
-62 -92 44.9897 0.000178 11.0103 3.55E-06 6.31E-10
-61 -91 45.9897 0.000199 12.0103 3.99E-06 7.94E-10
-60 -90 46.9897 0.000224 13.0103 4.47E-06 1E-09
-59 -89 47.9897 0.000251 14.0103 5.02E-06 1.26E-09
-58 -88 48.9897 0.000282 15.0103 5.63E-06 1.58E-09
-57 -87 49.9897 0.000316 16.0103 6.32E-06 2E-09
-56 -86 50.9897 0.000354 17.0103 7.09E-06 2.51E-09
-55 -85 51.9897 0.000398 18.0103 7.95E-06 3.16E-09
-54 -84 52.9897 0.000446 19.0103 8.92E-06 3.98E-09
-53 -83 53.9897 0.000501 20.0103 1E-05 5.01E-09
-52 -82 54.9897 0.000562 21.0103 1.12E-05 6.31E-09
-51 -81 55.9897 0.00063 22.0103 1.26E-05 7.94E-09
-50 -80 56.9897 0.000707 23.0103 1.41E-05 1E-08
-49 -79 57.9897 0.000793 24.0103 1.59E-05 1.26E-08
-48 -78 58.9897 0.00089 25.0103 1.78E-05 1.58E-08
-47 -77 59.9897 0.000999 26.0103 2E-05 2E-08
-46 -76 60.9897 0.001121 27.0103 2.24E-05 2.51E-08
-45 -75 61.9897 0.001257 28.0103 2.51E-05 3.16E-08
-44 -74 62.9897 0.001411 29.0103 2.82E-05 3.98E-08
-43 -73 63.9897 0.001583 30.0103 3.17E-05 5.01E-08
-42 -72 64.9897 0.001776 31.0103 3.55E-05 6.31E-08
-41 -71 65.9897 0.001993 32.0103 3.99E-05 7.94E-08
-40 -70 66.9897 0.002236 33.0103 4.47E-05 1E-07
-39 -69 67.9897 0.002509 34.0103 5.02E-05 1.26E-07
-38 -68 68.9897 0.002815 35.0103 5.63E-05 1.58E-07
-37 -67 69.9897 0.003159 36.0103 6.32E-05 2E-07
-36 -66 70.9897 0.003544 37.0103 7.09E-05 2.51E-07
-35 -65 71.9897 0.003976 38.0103 7.95E-05 3.16E-07
-34 -64 72.9897 0.004462 39.0103 8.92E-05 3.98E-07
-33 -63 73.9897 0.005006 40.0103 0.0001 5.01E-07
-32 -62 74.9897 0.005617 41.0103 0.000112 6.31E-07
-31 -61 75.9897 0.006302 42.0103 0.000126 7.94E-07
-30 -60 76.9897 0.007071 43.0103 0.000141 0.000001
-29 -59 77.9897 0.007934 44.0103 0.000159 1.26E-06
-28 -58 78.9897 0.008902 45.0103 0.000178 1.58E-06
-27 -57 79.9897 0.009988 46.0103 0.0002 2E-06
-26 -56 80.9897 0.011207 47.0103 0.000224 2.51E-06
-25 -55 81.9897 0.012574 48.0103 0.000251 3.16E-06
-24 -54 82.9897 0.014109 49.0103 0.000282 3.98E-06
-23 -53 83.9897 0.01583 50.0103 0.000317 5.01E-06
-22 -52 84.9897 0.017762 51.0103 0.000355 6.31E-06
-21 -51 85.9897 0.019929 52.0103 0.000399 7.94E-06
-20 -50 86.9897 0.022361 53.0103 0.000447 0.00001
-19 -49 87.9897 0.025089 54.0103 0.000502 1.26E-05
-18 -48 88.9897 0.02815 55.0103 0.000563 1.58E-05
-17 -47 89.9897 0.031585 56.0103 0.000632 2E-05
-16 -46 90.9897 0.035439 57.0103 0.000709 2.51E-05
-15 -45 91.9897 0.039764 58.0103 0.000795 3.16E-05
-14 -44 92.9897 0.044615 59.0103 0.000892 3.98E-05
-13 -43 93.9897 0.050059 60.0103 0.001001 5.01E-05
-12 -42 94.9897 0.056167 61.0103 0.001123 6.31E-05
-11 -41 95.9897 0.063021 62.0103 0.00126 7.94E-05
-10 -40 96.9897 0.070711 63.0103 0.001414 0.0001
-9 -39 97.9897 0.079339 64.0103 0.001587 0.000126
-8 -38 98.9897 0.089019 65.0103 0.00178 0.000158
-7 -37 99.9897 0.099881 66.0103 0.001998 0.0002
-6 -36 100.9897 0.112069 67.0103 0.002241 0.000251
-5 -35 101.9897 0.125743 68.0103 0.002515 0.000316
-4 -34 102.9897 0.141086 69.0103 0.002822 0.000398
-3 -33 103.9897 0.158301 70.0103 0.003166 0.000501
-2 -32 104.9897 0.177617 71.0103 0.003552 0.000631
-1 -31 105.9897 0.19929 72.0103 0.003986 0.000794
0 -30 106.9897 0.223607 73.0103 0.004472 0.001
1 -29 107.9897 0.250891 74.0103 0.005018 0.001259
2 -28 108.9897 0.281504 75.0103 0.00563 0.001585
3 -27 109.9897 0.315853 76.0103 0.006317 0.001995
4 -26 110.9897 0.354393 77.0103 0.007088 0.002512
5 -25 111.9897 0.397635 78.0103 0.007953 0.003162
6 -24 112.9897 0.446154 79.0103 0.008923 0.003981
7 -23 113.9897 0.500593 80.0103 0.010012 0.005012
8 -22 114.9897 0.561675 81.0103 0.011233 0.00631
9 -21 115.9897 0.63021 82.0103 0.012604 0.007943
10 -20 116.9897 0.707107 83.0103 0.014142 0.01
11 -19 117.9897 0.793387 84.0103 0.015868 0.012589
12 -18 118.9897 0.890195 85.0103 0.017804 0.015849
13 -17 119.9897 0.998815 86.0103 0.019976 0.019953
14 -16 120.9897 1.120689 87.0103 0.022414 0.025119
15 -15 121.9897 1.257433 88.0103 0.025149 0.031623
16 -14 122.9897 1.410864 89.0103 0.028217 0.039811
17 -13 123.9897 1.583015 90.0103 0.03166 0.050119
18 -12 124.9897 1.776172 91.0103 0.035523 0.063096
19 -11 125.9897 1.992898 92.0103 0.039858 0.079433
20 -10 126.9897 2.236068 93.0103 0.044721 0.1
21 -9 127.9897 2.50891 94.0103 0.050178 0.125893
22 -8 128.9897 2.815043 95.0103 0.056301 0.158489
23 -7 129.9897 3.15853 96.0103 0.063171 0.199526
24 -6 130.9897 3.543929 97.0103 0.070879 0.251189
25 -5 131.9897 3.976354 98.0103 0.079527 0.316228
26 -4 132.9897 4.461542 99.0103 0.089231 0.398107
27 -3 133.9897 5.005933 100.0103 0.100119 0.501187
28 -2 134.9897 5.616749 101.0103 0.112335 0.630957
29 -1 135.9897 6.302096 102.0103 0.126042 0.794328
30 0 136.9897 7.071068 103.0103 0.141421 1
31 1 137.9897 7.933869 104.0103 0.158677 1.258925
32 2 138.9897 8.901947 105.0103 0.178039 1.584893
33 3 139.9897 9.988149 106.0103 0.199763 1.995262
34 4 140.9897 11.20689 107.0103 0.224138 2.511886
35 5 141.9897 12.57433 108.0103 0.251487 3.162278
36 6 142.9897 14.10864 109.0103 0.282173 3.981072
37 7 143.9897 15.83015 110.0103 0.316603 5.011872
38 8 144.9897 17.76172 111.0103 0.355234 6.309573
39 9 145.9897 19.92898 112.0103 0.39858 7.943282
40 10 146.9897 22.36068 113.0103 0.447214 10
41 11 147.9897 25.0891 114.0103 0.501782 12.58925
42 12 148.9897 28.15043 115.0103 0.563009 15.84893
43 13 149.9897 31.5853 116.0103 0.631706 19.95262
44 14 150.9897 35.43929 117.0103 0.708786 25.11886
45 15 151.9897 39.76354 118.0103 0.795271 31.62278
46 16 152.9897 44.61542 119.0103 0.892308 39.81072
47 17 153.9897 50.05933 120.0103 1.001187 50.11872
48 18 154.9897 56.16749 121.0103 1.12335 63.09573
49 19 155.9897 63.02096 122.0103 1.260419 79.43282
50 20 156.9897 70.71068 123.0103 1.414214 100
51 21 157.9897 79.33869 124.0103 1.586774 125.8925
52 22 158.9897 89.01947 125.0103 1.780389 158.4893
53 23 159.9897 99.88149 126.0103 1.99763 199.5262
54 24 160.9897 112.0689 127.0103 2.241377 251.1886
55 25 161.9897 125.7433 128.0103 2.514867 316.2278
56 26 162.9897 141.0864 129.0103 2.821727 398.1072
57 27 163.9897 158.3015 130.0103 3.16603 501.1872
58 28 164.9897 177.6172 131.0103 3.552344 630.9573
59 29 165.9897 199.2898 132.0103 3.985795 794.3282
60 30 166.9897 223.6068 133.0103 4.472136 1000
61 31 167.9897 250.891 134.0103 5.017819 1258.925
62 32 168.9897 281.5043 135.0103 5.630086 1584.893
63 33 169.9897 315.853 136.0103 6.31706 1995.262
64 34 170.9897 354.3929 137.0103 7.087858 2511.886
65 35 171.9897 397.6354 138.0103 7.952707 3162.278
66 36 172.9897 446.1542 139.0103 8.923084 3981.072
67 37 173.9897 500.5933 140.0103 10.01187 5011.872
68 38 174.9897 561.6749 141.0103 11.2335 6309.573
69 39 175.9897 630.2096 142.0103 12.60419 7943.282
70 40 176.9897 707.1068 143.0103 14.14214 10000
71 41 177.9897 793.3869 144.0103 15.86774 12589.25
72 42 178.9897 890.1947 145.0103 17.80389 15848.93
73 43 179.9897 998.8149 146.0103 19.9763 19952.62
74 44 180.9897 1120.689 147.0103 22.41377 25118.86
75 45 181.9897 1257.433 148.0103 25.14867 31622.78
76 46 182.9897 1410.864 149.0103 28.21727 39810.72
77 47 183.9897 1583.015 150.0103 31.6603 50118.72
78 48 184.9897 1776.172 151.0103 35.52344 63095.73
79 49 185.9897 1992.898 152.0103 39.85795 79432.82
80 50 186.9897 2236.068 153.0103 44.72136 100000
81 51 187.9897 2508.91 154.0103 50.17819 125892.5
82 52 188.9897 2815.043 155.0103 56.30086 158489.3
83 53 189.9897 3158.53 156.0103 63.1706 199526.2
84 54 190.9897 3543.929 157.0103 70.87858 251188.6
85 55 191.9897 3976.354 158.0103 79.52707 316227.8
86 56 192.9897 4461.542 159.0103 89.23084 398107.2
87 57 193.9897 5005.933 160.0103 100.1187 501187.2
88 58 194.9897 5616.749 161.0103 112.335 630957.3
89 59 195.9897 6302.096 162.0103 126.0419 794328.2
90 60 196.9897 7071.068 163.0103 141.4214 1000000
91 61 197.9897 7933.869 164.0103 158.6774 1258925
92 62 198.9897 8901.947 165.0103 178.0389 1584893
93 63 199.9897 9988.149 166.0103 199.763 1995262
94 64 200.9897 11206.89 167.0103 224.1377 2511886
95 65 201.9897 12574.33 168.0103 251.4867 3162278
96 66 202.9897 14108.64 169.0103 282.1727 3981072
97 67 203.9897 15830.15 170.0103 316.603 5011872
98 68 204.9897 17761.72 171.0103 355.2344 6309573
99 69 205.9897 19928.98 172.0103 398.5795 7943282
100 70 206.9897 22360.68 173.0103 447.2136 10000000


 
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