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
