Decibels
Posted: Sat Jul 17, 2004 10:40 am
Decibels (dB) are commonly used to describe gain or loss in circuits. The number of decibels is found from:
Gain in dB = 10*log(gain factor) or
[img]http://www.hdtvprimer.com/ANTENNAS/decibels.gif[/img]
In some situations this is more complicated than using gain or loss factors. But in many situations, decibels are simpler. For example, suppose 10 feet of cable loses 1 dB of signal. To figure the loss in a longer cable, just add 1 dB for every 10 feet. In general, decibels let you add or subtract instead of multiply or divide. There are some special numbers you might want to memorize:
20 dB = gain factor of 100
10 dB = gain factor of 10
3 dB = gain factor of 2 (actually 1.995)
0 dB = no gain or loss
-1 dB = a 20% loss of signal
-3 dB = a 50% loss of signal
-10 dB = a 90% loss of signal
Gain in dB = 10*log(gain factor) or
[img]http://www.hdtvprimer.com/ANTENNAS/decibels.gif[/img]
In some situations this is more complicated than using gain or loss factors. But in many situations, decibels are simpler. For example, suppose 10 feet of cable loses 1 dB of signal. To figure the loss in a longer cable, just add 1 dB for every 10 feet. In general, decibels let you add or subtract instead of multiply or divide. There are some special numbers you might want to memorize:
20 dB = gain factor of 100
10 dB = gain factor of 10
3 dB = gain factor of 2 (actually 1.995)
0 dB = no gain or loss
-1 dB = a 20% loss of signal
-3 dB = a 50% loss of signal
-10 dB = a 90% loss of signal