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. -- To reply via email subtract one hundred and four