What is
Db The decibel (dB) is a unit ratio, the ratio of the power of a signal applied to an input power obtained at the output.
Such a relationship can be a gain if the existing power output is greater than that applied at the input or diminished if the output power is less than that applied at the input, that simple.
Decibels should be implemented on the basis of power but in BF (low frequency) signals to be amplified only in tension, it is more convenient to use as a base value TENSION.
example, if you want to measure the gain of an amplifier stage of BF, it is preferred to compare the voltage at the input to the output obtained.
example, if applied to the input of a pleamplificador a signal of 2.5 millivolts and obtain an output voltage of 14 mV we can say that this step gets a voltage gain equal to 14: 2.5 = 5.6 times , if we check the standards tables in a voltage gain of 5.6 equals 15 db.
In AF (high frequency) to work with known impedance values \u200b\u200b(50 or 75 Ohms) is advantageous in power calculation.
If you have an RF amplifier (RF) with a gain of 8 dB, looking at the standard tables we see that the power gain is of 6.31 times, therefore if we apply 3 watts entry in its output will 6.31 x 3 = 18.93 Watts.
If you have an antenna with a gain of 12 dB, looking at the tables we see that applying to a transmitter that will increase 15.85 times the radiation, so you can see the great difference in the power of a transmitter radiated power the same transmitter with antennas of different gains.
If we apply the same antenna of 12 dB at a receiver is also increased in 15.85 times the power captured.
The Db are useful for calculating gain or attenuation.
80cm offset antenna for receiving satellite in KU band adapted for radio relay transmitter to 1,600 MHz, 25 dB gain of approximately
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