It actually looks like the control channel for Motorola SmartNet is FSK: "On the control (data) channel the base station transmits 84 bits frames at 3600 bit/s with direct frequency modulation of the carrier using Frequency Shift Keying (FSK). "
I will at least see if I can get something that looks right out the other side. Would it be best to use one of the GFSK examples in gr-digital? On Fri, Oct 17, 2014 at 10:37 AM, John Malsbury < jmalsbury.perso...@gmail.com> wrote: > Also, my understanding for the PLL blocks were that they were ideal for > "strong carrier" signals like AM. When I say strong carrier i mean a > signal that has an obvious carrier which isn't "hidden" under modulation.. > > Anyway, the GMSK block might be a good place to start. > > -John > > On Fri, Oct 17, 2014 at 7:35 AM, John Malsbury < > jmalsbury.perso...@gmail.com> wrote: > >> It doesn't have frequency correction - I can probably follow up with some >> ideas on how to implement that part. But the GMSK demod might do OK for >> you initially. It doesn't do anything intelligent to deal with the data >> shaping - its just a non-coherent slicer. >> >> If you want to design in GRC but keep your top-level application as is, >> you can use a hier block. You can also use a command line parameter or >> other mechanism to select your demodulator at start-time for easy >> comparisons. >> >> [typed one handed.. my daughter has my other and] >> >> -John >> >> On Fri, Oct 17, 2014 at 7:08 AM, Luke Berndt <l...@robotastic.com> wrote: >> >>> Thanks for looking into it! To be honest, I am not really good at RF. I >>> based my code off the python code in gr-smartnet. The fsk-demod python file >>> is here: >>> https://github.com/bistromath/gr-smartnet/blob/master/src/python/fsk_demod.py >>> >>> It is quite possible that it just happened to work because of an error >>> that got patched in Gr 3.7. >>> >>> Are there some good examples for GMSK/FSK demodulation that I could >>> borrow from instead? >>> >>> Recreating this in GRC sounds like a great idea so I can scope along the >>> way. I will give that a try next. >>> >>> Thanks again for the pointers, fresh eyes are really helpful when you >>> have been staring at it for so long. >>> >>> - Luke >>> >>> On Fri, Oct 17, 2014 at 8:18 AM, Martin Braun <martin.br...@ettus.com> >>> wrote: >>> >>>> On 10/17/2014 08:28 AM, John Malsbury wrote: >>>> > Also also, is the Band-Edge FLL ideal for GMSK? My possibly, >>>> incorrect >>>> > understanding of that block is that it was more ideal for PAM with >>>> > common RRC. >>>> >>>> For the record: It might work coincidentally because of the rolloff-y >>>> shape of GMSK, but it's derived for and designed for common PAM/RRC, as >>>> John says and I wouldn't recommend it for anything else. >>>> To look up the math, I suggest Harris' works. >>>> >>>> >>>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >> >
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