Re: [Discuss-gnuradio] Funcube dongle issues and a solution

[Gasper Zejn]

Dne Thursday 07 June 2012 ob 22:38:51 je Alexandru Csete napisal(a):
> On Thu, Jun 7, 2012 at 10:27 PM, Gasper Zejn <address@hidden> wrote:
> > Dne Thursday 07 June 2012 ob 21:59:24 je Alexandru Csete napisal(a):
> >> On Thu, Jun 7, 2012 at 11:13 AM, Gasper Zejn <address@hidden> wrote:
> >> > a bit more on my setup: I'm using funcube as a source, tuned to
> >> > 868.48M, LNA gain 20dB, mixer gain 12dB, connected to simple squelch
> >> > (threshold=-40dB, alpha=1) and on to quadrature demodulation block.
> >> > This block then outputs clearly visible binary signal when funcube is
> >> > initialized properly.
> >> > 
> >> > The observed signal is rated at 20kbit, so it's a bit on the upper
> >> > limit of what Funcube can do, but it's still possible to get a decent
> >> > read. It's a burst of bits every 5s from a power meter[1][2], and the
> >> > first part is a lead- in and stays the same even if readings change.
> >> > 
> >> > Somewhere in the funcube source block there is obviously something
> >> > wrong with initialization. Running qthid after starting flow changes
> >> > something in funcube that makes it output correct signal. Using this
> >> > and the fact, that the lead-in stays the same, it seems the "corrupt"
> >> > signal (viewed in scope) is sometimes a derivative of the expected
> >> > signal - most of the time on zero, with spikes up and down on
> >> > transitions, with timing corresponding to transitions in expected
> >> > signal.
> >> 
> >> Do you have the same frequency correction value in both qthid and the
> >> FCD source? If yes, what is the value?
> >> 
> >> Alex
> > 
> > Ahh, yes. I had 0 in my flow and qthid was -120.
> > 
> > So sorry to waste your precious time.
> 
> No problem, time wasn't wasted since there is actually a bug in the
> init part of fcd_source_c.xml: it checks whether correction is 115
> whereas it should check -120, but this bug is only triggered if your
> initial correction is set to 115 ppm.
> 
> I also realized that I never added 1 Hz resolution to qthid.
> 
> Alex
> 

Ah, that explains something then.

I remember experimenting with correction, but I was looking at 
fcd_source_c.xml and, influenced by it, used 120 instead of -120, therefore 
not getting correct result and dismissing it as not the right parameter to 
tune.

Any way, it's allways nice to see bugs fixed. :)

Gasper