dB Ruler
dB Ruler, developed by Temcom and sponsored by Livingston
Getting started : Choose conversion mode (dB, dbm, vswr or V/m W/m²) by clicking to the selector arrow. Enter the value to convert in the field corresponding, then press the key ' = ', the two other values will be dispalyed in their respective fields. You can enter the value to convert in the form of calculation (1.3+ 5.6 + 25.8; 30/9; ....) or of scientific representation (1e9; ....). The "Clear" key erases the three displays.
The value of the ''Ohm'' display is preset to 50 ohms, can be modified by entering another value. (Only necessary for conversions dBm  W > V and dBV  dBm  dBµA W/m²  V/m)
For V/m <   > W/m² conversion, the reference is set automatically 376.73 ohms (free space impedance) and to the previous value for other modes. The reference impedance can be modified by clicking in the display and entering the requested value.
The dB is the logarithlmic expression of a ratio between two power levels. 1 dB = a tenth of one Bel.
1 Bel corresponds to ratio of 10 = 10 ^{1}.
If the power ratio between output /input of a device is 100 (= 10^{2}) the the gain is 2 Bel or 20 dB.
Bel = log(P_{2}/P_{1})
As the power follows a square low function of the voltage, the voltage calculation for
Bel = 2 log (U_{2}/U_{1}) ... condition : input and output impedance has to bethe same!
The dBm corresponds to the dB referred to 1 mW ( 30 dBm = 10^{3 } mW = 1000 mW and the dBV is referred to 1V (+40 dBV = 10^{4/2} = 100V)... 100 times (10^{2}) more voltage results in 10.000 fois (10^{4}) more power.
10^{0,301} = 2 ; 0,301 Bel (approx 3 dB) corresponds to a gain of 2 ; and 10^{0,301} Bel to 0,5...... (half the power)... 6 dB (two times 3 dB) = 4 times the power and 2 times the voltage.
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