OK, all set! Cheers Gerhard -----Ursprüngliche Nachricht----- Von: David Rowe [mailto:[email protected]] Gesendet: Freitag, 03. Februar 2017 11:52 An: [email protected] Betreff: Re: [Freetel-codec2] FreeDV 700C early release
Yes I agree Helmut - it's the hard amplitude limiting of the cohpsk modulator waveform. It's present in the modulator output, before the PA. Cheers, David On 03/02/17 19:16, Helmut wrote: > Hi David, > > I don't believe that this mentioned noise plateau - approx. 32 dB > below peak > - of mode 700C inside the communication channel is caused by amps. > Probably its caused by the modem itself. > > I run my amps with high efficient linearization due to predistortion - > currently a new advanced beta version - achieving 60 dB IMD! Moreover > the inside channel noise plateau is also independent of the drive > level or amp output. > > 73, Helmut, DC6NY > > > > > -----Ursprüngliche Nachricht----- > Von: David Rowe [mailto:[email protected]] > Gesendet: Freitag, 3. Februar 2017 07:15 > An: [email protected] > Betreff: Re: [Freetel-codec2] FreeDV 700C early release > > Hi Gerhard, > > This actually dovetails neatly with Steve's PAPR work in the last post > to this list. > > Unlike the 1600 and 800 modes, the COHPSK modulator used for 700C has > some clipping on the output to improve the PAPR. In some PAs, this > means you get get a higher average power output. In others, it may > let the smoke out. > > This amplitude limiting is a form of non linearity and is probably the > cause in the spectral regrowth at the edges of the spectrum that you > are observing. > > Clipping can be disabled in the FreeDV GUI program Tool-Options menu. > > Cheers, > > David > > > On 03/02/17 16:26, Gerhard Burian wrote: >> Hi David, >> >> When I was testing the different modes with websdrs I recognized >> higher sideband noise (shoulders) in 700C mode compared with 800XA >> and 1600 mode > at >> the same settings on my ANAN-100D. I am using narrow filtering on TX >> and pure signal. So I don't have an explanation for that. >> >> Regards >> Gerhard >> >> -----Ursprüngliche Nachricht----- >> Von: David Rowe [mailto:[email protected]] >> Gesendet: Dienstag, 31. Jänner 2017 11:40 >> An: [email protected] >> Betreff: Re: [Freetel-codec2] FreeDV 700C early release >> >> I been sending a few SSB/700C test signals of 800 - 1500 km paths on >> 40M using a websdr to pick them up at the other end. In marginal >> conditions with SSB down in the noise I'm getting sync and audio through on 700C. >> Not sure if I have the same average tx power though. >> >> Also had a 700C QSO with a guy interstate. SSB very noisy but 6-8dB >> SNR > on >> 700C. Noise free but some issues with his audio and the modem >> loosing > sync >> every few seconds. >> >> Lot of frequency selective fading in both tests. >> >> Promising start.... >> >> - David >> >> > ---------------------------------------------------------------------- > ------ >> -- >> 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 >> [email protected] >> 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 >> [email protected] >> 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > --- > Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. > https://www.avast.com/antivirus > > > ---------------------------------------------------------------------- > -------- 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 > [email protected] > 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 [email protected] 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 [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
