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> Math Question, dBW
Audiotek
Posted: November 03, 2011 02:26 am
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I'm having a blank.

The input to a power amplifier is 0.1W and the output is 20W. What is the gain of the amplifier in dB? I have the answer but I'm missing a step tongue.gif
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Audiotek
Posted: November 03, 2011 04:05 am
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I'm having issues with the log

http://www.satcom.co.uk/print.asp?article=10
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GPG
Posted: November 03, 2011 04:46 am
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20/.1 = 200
10log200 = 23dB
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Audiotek
Posted: November 03, 2011 12:09 pm
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Great thanks
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GPG
Posted: November 03, 2011 11:26 pm
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You don't even need a calculator for ths.
log 100 = 2, log 2 = .3 add and multiply by 10
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Colt45
Posted: November 04, 2011 09:54 am
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You arent asking for dBW...

anyway, you can do it the moron way

a ten fold increase is +10dB (exactly)
a two fold increase is +3dB (close, its a portion of a percent out)

so .1 -> 1 -> 10 -> 20
is +10 +10 +3
= 23dB


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GPG
Posted: November 04, 2011 11:12 am
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I resent beiing called a moron. I knew that he wanted dB power gain and the method outlined above resembles your "moron" method.
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Colt45
Posted: November 05, 2011 02:06 am
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I call it moron way because that's how I do it wink.gif
With it you don't need logs, and it doesn't work for everything, more of an approximation technique.


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Sch3mat1c
Posted: November 05, 2011 07:07 pm
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Not at all moronic really, Fermi and Feynman were famous for approximating calculations mentally. I try but I'm certainly slow, usually getting a couple of the most significant digits while searching for a calculator (when one isn't immediately to hand).

Tim


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Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.
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