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

                        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