Exactly what I was looking for. Thank you! -Jordan
On Thu, Aug 20, 2015 at 3:05 PM, Dominic Spill <[email protected]> wrote: > On 20 August 2015 at 15:42, Jordan Kagan <[email protected]> wrote: > > > > So in short I am wondering why one wouldn't just choose the center > frequency > > to be the FM channel frequency or a frequency in the range of interest. > > A great question and one that causes confusion for many people. It's > discussed in the HackRF FAQ, but from a different angle (i.e. "how do > I solve problem X?" "offset the centre frequency"). > > If you start gqrx or any other tool that shows an FFT of the received > data, you will notice a large spike in the centre of the display. > This is the 0Hz component of the received signal, also known as the DC > offset or DC bias. It's a side effect of the quadrature sampling > technique and is just something that we have to live with. This is > discussed here: > > https://github.com/mossmann/hackrf/wiki/FAQ#what-is-this-big-spike-in-the-center-of-my-received-spectrum > > The following FAQ question is about how to deal with it: > > https://github.com/mossmann/hackrf/wiki/FAQ#how-do-i-deal-with-the-dc-offset > > The tl;dr of that question is: offset the centre frequency of the > radio and then shift it back in software. This is what those > flowgraphs are doing. > > I hope that answers the question, although if you would like more > detail, I'm sure someone on this list can answer it better than I can. > > Thanks, > Dominic >
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