How to Use Decibels (dB & dBm) for Strong & Weak Signal Strength in Communication Systems.
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How to Use Decibel, dB & dBm to Represent a Strong or Weak Signal in a Communication System.
When we express numbers in deciBel (dB), the student always has an idea that we either “add” or “subtract” (modify) the strength of the signal in a communication system.
However, we do not really change the numerical value of the number, but we just used different forms to represent the number.
Example
10,000 cm = 100 m = 0.1 km
Why we need to express number in Decibel?
Signals in communication have extremely wide ranges (Very very small or very very big numbers) in magnitudes which make graphical representation and relative comparison between signals very difficult.
Example
An input signal having a power level of Si = 1 x 10-12 (0.000000000001) watts and an output signal power level of So = 0.001 watts
Ratio of So /Si is equal to 109 which is 1000000000
It is very cumbersome to operate with such big numbers and is also very prone to arithmetical errors!
The decibel scale is used to solve these problems.
It is a relative power measurement. Which means comparison between these 2 terms.
Advantages of using decibel scale
Less prone to arithmetical errors with very big/ small numbers and easier relative comparison between signals
Easier calculation when comes to multistage system
dBW = absolute power level of a signal referenced to a power level of 1W.
dBm = absolute power level of a signal referenced to a power level of 1mW.
dBV= absolute voltage level of a signal referenced to a voltage level of 1V.
dBmV= absolutevoltage level of a signal referenced to a voltage level of 1mV.
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