On Mon, 2014-11-03 at 12:01 -0500, [email protected] wrote: > 6. Re: Works with GR 3.6, breaks with 3.7 (Luke Berndt) > > On the off chance that someone has some free time to look into this, I > have built the Smartnet trunk control channel in GRC. I have also made > a capture of the signal. Everything is working the way it does on my C > ++ program. It is able find a lot of frames where the preamble > matches, but barely any of them bas the CRC test. The expected > behavior is that there would be 2-3 frames that pass the CRC test > every second, and that is how it works under 3.6.5. > > The SmartNet stuff is rolled into 3.7 blocks. Git clone, cmake . , > make, sudo make install > > If anyone sees some obvious mistakes let me know. I know this not the > ideal way to decode an FSK signal, but it works perfectly in 3.6.
Hi Luke, I have not built the SmartNet blocks yet, but: Your low pass filter looks way too wide and you'll get aliases when you decimate by 185. 2 Msps / 185 = 10.81 ksps, so the Nyquist frequency is 5.405 kHz. I winged this is as a low pass filter and things looked better: firdes.low_pass_2(1, samp_rate, 4500, 1000, 60, firdes.WIN_HANN, 6.76) The 60 dB down may be overkill, you can make it smaller for a filter with less delay. I found an offset slider value of -15k made things look about centered manually. You might want to put a waterfall sink before and after the FLL Band-Edge filter to observe how it is making the spectrum wobble around a little. If you change your offset slider, you can see the FLL band-edge filter centering things back up; so that looks like it is working. Regards, Andy > Thanks for any pointers people have! > > > Capture of the signal: > http://we.tl/ZMD8R5uQfR <http://we.tl/ZMD8R5uQfR> > > GRC Blocks for Smartnet > https://github.com/robotastic/gr-smartnet > <https://github.com/robotastic/gr-smartnet> > > > > GRC to decode Smartnet Tunking channel > > > > > > On Oct 20, 2014, at 3:19 AM, Martin Braun <[email protected]> > wrote: > > > > On 10/18/2014 05:57 PM, Luke Berndt wrote: > >> The Band Edge FLL works great for me too, on 3.6. Does anyone know > if > >> there were changes to it or surrounding blocks in 3.7 that would > make it > >> stop working? > > > > None of the DSP was changed, if it worked before it should(TM) still > > work. The reason we say it's a bad choice is that it was derived for > > PSK/PAM signals. The reason it still might work is that the > > implementation runs 2 filters at the band-edges and compares the > energy > > content of those, and that difference might be sufficient to correct > > your frequency offset if you have sufficient averaging (i.e. low > enough > > loop bandwidth). > > > > M > > > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > [email protected] > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > - _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
