The AirSpy uses the R820T2 chip for the tuner, but a different
sampling/DSP "engine".
Yes, making the charge-pump and "dither" mods will help with
phase-coherence.
Somebody needs to "own" the rtlsdr driver, and merge in the last couple
of years of field experience and branching that has gone on with it.
On 2016-05-25 15:04, Piotr Krysik wrote:
> Hi Marcus,
>
> I don't know much about AirSpy.
>
> Does it use the same demodulator chip as current RTL-SDR dongles?
> And does it mean that change to low level part of rtlsdr driver might
> help to get rid of that frequency offset?
>
> --
> Piotr
>
> W dniu 25.05.2016 o 16:35, mle...@ripnet.com pisze:
> There are a couple of issues with the rtlsdr driver used by gr-osmocom
> in this regard:
>
> (A) The charge-pump loop current is too constrained for the higher
> frequencies
>
> (B) The "dither" option appears to have a bias that causes a (small)
> frequency offset.
>
> The driver that AirSpy uses fixes both of these, although without
> "dither", the tuning granularity is worse. Not sure this matters.
>
> On 2016-05-25 09:28, Marcus Müller wrote:
>
> That, or simply, the output clock VCO changes its reaction to the
> control voltage under certain circumstances (temperature, frequency) so
> much that the control loop loses the ability to reach stationary
> exactness (e.g. due to natural limits on the magnitude of the VCO
> voltage). These devices definitely were made with cost in mind - not
> with maximum reliability, and hence I can believe that for example with
> the Elonics E4000 tuner, the charge pump used to generate the VCO
> voltage simply might deteriorate with temperature.
>
> Cheers,
> Marcus
>
> On 25.05.2016 14:25, Sylvain Munaut wrote: Hi,
>
> of the drift remains a mistery (probably due to the implementation
> of the PLL,
> but I cannot understand why Phase Locked Loops would drift in Phase !). If
> the phase comparator is digital ( i.e. a XOR ) and the input clock
> is somewhat analog, the gate thresholds might vary depending on
> temperature, thus shifting the cycle a bit.
>
> Just a thought.
>
> Cheers,
>
> Sylvain
>
> _______________________________________________
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
