Assuming the difference is small enough, this is a normal RX problem that a GMSK demod should be able to handle. The labels on your frequency plot do not say what the offset is, but hint that it is small. Take a look at gmsk.py <https://github.com/gnuradio/gnuradio/blob/b76e8788687b4feef610e501c0c7d167c4f04a98/gr-digital/python/digital/gmsk.py#L165> to see how it's handled in the built-in demod.
On Wed, Jun 24, 2020 at 4:10 PM Artur Nogueira <artur.no...@gmail.com> wrote: > Hi Jeff, > > Thanks for the feedback. > I'm using GNU Radio Version 3.7.13.5 and two Great Scott Gadgets HackRF > units for the transmission/reception. > My workflow looks like this: > > [image: image.png] > > Do you usually use any artifact to compensate for this frequency shift? > I'm afraid this could affect demodulation and therefore the BER. > > Best regards, > Artur > > > Em qua., 24 de jun. de 2020 às 16:31, Jeff Long <willco...@gmail.com> > escreveu: > >> Artur, >> >> You haven't mentioned what software you are using, how you have it >> configured, or what your flowgraph looks like. >> >> If you are using two SDRs and the frequency difference is a few kHz, then >> that is just oscillator differences. >> >> On Wed, Jun 24, 2020 at 3:12 PM Artur Nogueira <artur.no...@gmail.com> >> wrote: >> >>> Hi everyone, >>> >>> I'm comparing the spectra of a pair of transmitted/received GMSK signals >>> (carrier frequency = 923 MHz). >>> As expected, there is a certain channel attenuation. >>> Nevertheless, there is this frequency deviation at the Osmocom Source >>> output: >>> [image: image.png] >>> >>> I suppose this is something related to the receiver hardware. >>> Do you have a suggestion on how to compensate for this effect at a >>> software level? >>> >>> Best regards, >>> Artur >>> >>>
