[Elecraft] K3 dbV in 2.38

[Alan Bloom]

> Into a linear load, and I presume we have one here[A], there is no 
> difference between dB relative to a voltage, using the 20 log10, 
> voltage, formula and dB relative to the power corresponding to that 
> voltage using the 10 log10. power, formula.

That's only true if the source and load impedance are equal.  For
example, if an amplifier has a high-impedance input and a near-zero-ohm
output, then the power gain (in dB) is almost infinite even if the
voltage gain (in dB) is small.

That's probably why Elecraft chose the dBV notation to mean "deciBels of
voltage gain" even though it might be confused with the official
meaning, "deciBels relative to 1.0 volt".

Al N1AL


On Wed, 2008-09-17 at 00:03, David Woolley (E.L) wrote:
> Lyle Johnson wrote:
> 
> > 
> > We have a total of three characters available, and we wanted to express 
> > that this was a dB value, and it was voltage based.  So we used dBV.
> 
> Into a linear load, and I presume we have one here[A], there is no 
> difference between dB relative to a voltage, using the 20 log10, 
> voltage, formula and dB relative to the power corresponding to that 
> voltage using the 10 log10. power, formula.  The difference between 10 
> and 20 is to account for the need to square the voltage to get the power.
> 
> In this case the units should be bare dB.  You will still have problems 
> because of the large number of people who don't know the definition of a 
> dB and are only used to seeing dB's relative to some defined standard.
> 
> 
> [A] strictly speaking the load at any one stage could be non-linear, as 
> long as the total system, through to the air outside the speaker 
> believes in a linear way.