[hpsdr] Mercury sampling rate

[Henry Vredegoor]

Hi Alberto,

Isn't this an issue with matching the SDR hardware's (Mercury's) sampling
rate to the common SDR programs possibilities wrt. sampling rate ?
Aren't these most of the time fixed to common soundcard standard sampling
rate's? (like 44,1 - 48 - 96 - 192 Ks/sec etc.)

Henry.

> -----Original Message-----
> From: hpsdr-bounces at lists.hpsdr.org 
> [mailto:hpsdr-bounces at lists.hpsdr.org] On Behalf Of Alberto I2PHD
> Sent: zaterdag 12 april 2008 16:26
> To: hpsdr at lists.hpsdr.org
> Subject: Re: [hpsdr] Mercury sampling rate
> 
> 
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Phil Harman wrote:
> >  
> > We sample at 122.88MHz since that divides evenly to 
> standard sound card 
> > frequencies.  This does need updating since we will be able 
> to achieve 
> > 2MHz of displayed bandwidth using the current USB2 
> interface to the PC.
> >  
> > 73's Phil...VK6APH
> 
> May I ask the rationale behind that ? The data sampled by the 
> ADC are of course not meant to be passed through a sound 
> card after the decimation... they are already digital. And 
> for the output you need always to use a fractional resampler 
> as you cannot have any guarantee that the sampling rate of 
> the output sound card is an *exact* submultiple of the 
> downsampled rate. And, once you have accepted the need of a 
> fractional resampler, then any ADC clock frequency can be 
> used.
> 
> Or maybe I am missing part of the picture ?
> 
> 73  Alberto  I2PHD
> 
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