[LAU] Jack sample-rate

[Will Godfrey]

On Mon, 14 Dec 2015 16:46:47 +0000
Adam Sampson <ats at offog.org> wrote:

> Will Godfrey <willgodfrey at musically.me.uk> writes:
> 
> >> Not for audio, but having JACK run at 96000 Hz is quite useful for
> >> low-cost software-defined radio...
> > Explain.... please.
> 
> A common architecture for an SDR receiver uses a quadrature sampling
> detector: you mix the incoming radio signal with a pair of clocks 90
> degrees apart, and sample the two resulting signals (I/Q).  Some DSP
> then allows you to "tune in" any signal within the bandwidth that you've
> sampled -- if my detector's clock is running at 7 MHz and I'm sampling
> I/Q at 48 kHz, my SDR receiver can demodulate any signals between 6.976
> MHz and 7.024 MHz (and can receive several signals simultaneously
> provided they're within that range of frequencies).
> 
> So the advantage of sampling at a higher rate is that you can receive a
> wider chunk of the radio spectrum without having to retune. High-end SDR
> receivers have a dedicated ADC that can run at a high sampling rate, but
> cheap radios like the SoftRock kits (http://wb5rvz.com/sdr/) use a
> regular soundcard.
> 
> I'm using a SoftRock RXTX with dttsp (and sdr-shell/softrig/fldigi),
> which uses JACK for audio IO. Running JACK at 96 kHz for this means that
> I can see most of the 30m amateur band at the same time...
> 
> Cheers,
> 

Thanks for the explanation. Very interesting stuff :)

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.