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MathGroup Archive 2005

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Re: something like dB

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56629] Re: something like dB
  • From: Bill Rowe <readnewsciv at earthlink.net>
  • Date: Sat, 30 Apr 2005 01:28:36 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

On 4/29/05 at 3:20 AM, djmp at earthlink.net (David Park) wrote:

>It is only sloppyness to say that something is x dB. (Maybe I'll
>hear differently from other responders.) In any case, if you use
>0.0 dB then the 0.0 will be retained, but if you write exact 0
>anything Mathematica always returns 0.

No, it isn't just sloppyness to use dB. For example, it is perfectly logical to talk of an attenuation or gain of say 3 dB which would mean for attenuation half of the input power is lost. Linear amplifiers increase power by a fixed ratio for a given setting and attenuators decrease power by a fixed ratio. 

This is made even more useful by measuring power levels in units like dBm. Here the m tells me the power level is referenced to 1 mW. So, 0 dBm would be 1 mW of power. And with an input of 0 dBm and an amplifer with a gain of 30 dB, I can easily determine the output power is 30 dBm or equivalently 1 Watt.
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