[Elecraft] DSP - 4 questions

[Bill Coleman]

On 5/8/03 8:32 PM, Lyle Johnson at wa7gxd@fidalgo.net wrote:

>Your ears may be much better than mine. I don't hear any increase in noise
>floor, nor do I measure one. If I use the sig gen, the weakest signal I can
>discern is no different with DSP or without.  The quality of the signal and
>its apparent signal-to-noise ratio does change though, in most cases in
>definite favor of having the DSP.

This is good news. 

It is something to be sufficiently concerned enough to try and measure. I 
believe the original W9GR DSP used only an 8-bit CODEC, which caused a 
significant addition of quantization noise. 

Telephone CODECs are compandored (A-law or mu-law) to an equivalent of 
14-bits. Perhaps 16 bits is sufficient for radio, so long as it follows 
the major selective element and the AGC. For rigs with IF DSPs providing 
all the selectivity, dynamic range is the achillies heel -- hence the 20 
to 24-bit CODECs.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901