[Elecraft] AM with FM filter

[Don Wilhelm]

Joe and all,

BUT, doing it mathematically can produce an ideal waveform.  That is 
something difficult to accomplish with analog components which have 
inherent non-linearity and harmonic generation that is absent in the 
pure mathematical treatment.  The downside of doing it mathematically is 
in the conversion from the continuous analog stream to the "number soup" 
that must occur and then back again to analog.

The one opposing argument is that the digital treatment has finite bin 
sizes and moves stepwise from one bin to an adjacent bin - analog covers 
the same ground in a continuous manner with no steps.
The more bits in the ADC (or DAC), the closer the digital can be to an 
analog signal, but there still will be stepwise changes in the (number 
represented by the amplitude) in any digital transformation - digital 
smoothing helps a great deal, but is never perfect.

Which is better depends on the listener's ears - most listeners cannot 
determine the difference.  Consider the "better" audio quality of CDs as 
opposed to vinyl disks (I know there are some that will differ and 
consider the analog "better", but digital can preserve the full dynamic 
range and impulses where the analog can squash the peaks).  Also give 
consideration to the fact that MP3s have been touted by some as "more 
Hi-Fi" than CD quality! (Yes, I have seen those claims).  That is 
perception alone - a compressed signal cannot carry the full information 
of the original content no matter what the advertizing hype may 
indicate.  Many such things are only in the ears and mind of the 
listener - same goes with analog modulation vs. digitally generated 
signals - (yes, even CW is a form of modulation although not usually 
thought of as such).

73,
Don W3FPR

On 11/7/2011 10:16 PM, Joe Subich, W4TV wrote:
> It's still nothing more than doing mathematically what was previously
> done in circuitry.
>