Hi, IMO objective and severe comparison in presence of interference can only succeed using appropriate SDR hardware. These USB sticks are not developed for narrow bandwidths due to very low SFDR, phase noise of LO etc.
73, Helmut -----Ursprüngliche Nachricht----- Von: Adrian Musceac [mailto:kanto...@gmail.com] Gesendet: Montag, 18. September 2017 11:01 An: freetel-codec2@lists.sourceforge.net Betreff: Re: [Freetel-codec2] Comparison between digital voice and analog narrowband FM on weak signals with interference Hi, Helmut, for me RTL-SDR support is required. I will not be testing with another SDR hardware for reception as my application is meant to work with the USB stick (small dynamic range or not). Glen, have a look at http://www.etsi.org/deliver/etsi_etr/300_399/30001/01_60/etr_30001e01p.pdf specifically section 6.2.2 and below. Faces exactly the same issues. FM is also affected by fast Rayleigh fading.. Anyway, Doppler shift will be a bigger issue than multipath. Cheers, Adrian On 9/18/17, glen english <g...@cortexrf.com.au> wrote: > HI Adrian > > good stuff! > > OK, now try the analog versus the digital, with a copy of the TX > signal at 30uS delay and -10dB with respect to the wanted signal.... > (a common multipath ) , and also 30uS delay and 0dB. > > Let me know... > > > On 15/09/2017 9:10 PM, Adrian Musceac wrote: >> Hi, >> >> I present a three way comparison between narrow band FM (5 kHz), QPSK >> Codec2 1300 (2.4 kHz) and QPSK Opus 19 kbit/s (16 kHz): >> >> https://www.youtube.com/watch?v=vApRe6R1gnk >> >> The comparison is taking place in the ISM band of 433 MHz with >> interference present from some temperature sensors in an adjacent >> channel. >> >> Conditions: same antenna locations, same RX chain gain, varying >> transmit gain (LCD like number on the top left of the screen) >> >> Results: both digital modes cope better with interference and are >> more intelligible than FM. The numbers on top left of RX application >> are expressed in dB of amplification in the SDR transmitter chain. >> >> Hardware: for transmit one USRP B200 with 433 MHz filter installed, >> for RX one RTL-SDR filter with 433 filter installed. >> Software: QRadioLink running on top of Gnuradio (GNU/Linux): >> https://github.com/kantooon/qradiolink >> >> 73, >> Adrian YO8RZZ >> >> >> --------------------------------------------------------------------- >> --------- Check out the vibrant tech community on one of the world's >> most engaging tech sites, Slashdot.org! http://sdm.link/slashdot >> >> >> _______________________________________________ >> Freetel-codec2 mailing list >> Freetel-codec2@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > > ---------------------------------------------------------------------- > -------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ---------------------------------------------------------------------------- -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
