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

[Alexandru Csete]

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