On 19/01/2016 22:33, Jim Brown wrote: > On Tue,1/19/2016 1:57 PM, Bill Somerville wrote: >> >those Xonar numbers don't sound like dB figures, at least that's what I >> >assume since 70dB would be unrealistically high. > dB with no reference is simply the 10x the log of the ratio of two power > levels. If the impedance is the same, it is 20x the log of the ratio of > two voltage levels. 70 dB could, for example, be the voltage gain of an > amplifier. > > dBv is an actual voltage referenced to 1 volt, independent of impedance. > dBu is an actual voltage referenced to 0.78 volt, independent of > impedance. dBmw is actual power referenced to 1 mw, and includes the > impedance of the circuit. dBuV is the voltage referenced to 1 microvolt. Hi Jim,
all perfectly correct but not normally relevant in the discrete and finite digital domain. 0dB is normally taken as the output of the digital source i.e. a digital synthesiser or most commonly an ADC. Any gain or attenuation from that 0dB level equates to a loss of resolution with the exception that a stream that, for example, never reaches half the linear digital amplitude could be amplified by 3dB (multiplied by two) without losing any information. This is why 0dB is a good setting for an intermediate stage n a digital system because it represents passing the data unchanged. 73 Bill G4WJS. ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
