[hpsdr] ADC Question

[Larry Gadallah]

On 24 July 2012 13:50, Alberto I2PHD <i2phd at weaksignals.com> wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
>
>  On 7/24/2012 9:40 PM, Bill Tracey wrote:
>
> In short, you have to rejigger the firmware to present 48/96/192 khz
> samples to the PC.  I have a suspicion it's may not be trivial to do
> a non integral decimation in the firmware.
>
>  Is there really such a constraint ? Why the software running on the PC
> must be fed with
> 48/96 or 192 kHz samples ? Aren't those rates an heritage from the sound
> card era ?
> Take for example Perseus.  Its DDC sends to the PC rates of 125, 250, 500
> kHz,
> 1M or 2M samples/sec.  Both the original Perseus software and my Winrad
> are perfectly
> capable to cope with those rates.  IMHO there is nothing magic with
> 48/96/192 kHz.
>
> --
> *73 Alberto I2PHD*
>


I kind of agree with Alberto here: In addition to the Perseus, Phil
Covington's QS1R also has a wide variety of non-integral sampling rates
available. In my astonishingly small knowledge of DSP techniques, I know
that non-integral resampling is a difficult task, but non insurmountable.
Phil and Alex have been working recently on improving the sampling rates,
and this happens to be one of my biggest wish list items, so it would be
good if we could somehow break away from the soundcard heritage and start
to take advantage of the true capabilities of the hardware (i.e. CW Skimmer
Server and 5-band WSPR beacon).

All of this kind of leads to a supplemental question: How much of this
"integral of 48 kHz" is baked right into the architecture?

Cheers,
-- 
Larry Gadallah, VE6VQ/W7                          lgadallah AT gmail DOT com
PGP Sig: B5F9 C4A8 8517 82AC 16B6  02B6 0645 69F0 1F29 A512
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