On 08/11/2014 11:35, nick wrote:of BFO Hi Nick & All, > I like the empirical approach Paul! > > Your results pretty much correspond with my observations. > > The softrock and sdr-core combination goes all the way down to 0Hz. I > run the softrock LO with a 12kHz offset to get away from DC and the LF > limit of the Delta 44 sound card. > > I will start logging at < 250Hz and see what happens. You might try tuning up to ..078.5 (e.g. 14.0785 MHz) and running JT9 for these tests. I suggest it due to the bandwidth of the signal being a much smaller proportion of the audio frequency range you want to test. That way you will get a much better indication of the lower limit. Having said that, in both cases (JT65 & JT9) the sync tone is at the LF end of the signal and detection of that is fundamental to decoding.
Joe K1JT will have a definitive answer, but I wonder if the DF is in any way proportional to the resolving capability of the WSJT-X decoders. If not then there is no theoretical lower limit and any limiting effects would be down to secondary factors like roll off in SSB demodulator and any audio circuits and of course the obvious filtering of the BFO. There is another issue to consider, if you transmit very near your Rx DF zero you may get a reply below your DF zero which you will not decode so working near DF zero is not necessarily a good idea. > > 73 > > Nick G3VNC 73 Bill G4WJS. > > On 08/11/14 07:36, Paul DU2/WA8UGN wrote: >> Paul DU2/WA8UGN <keatipa@...> writes: >>> I have had WSJT-X v1.4.0-rc2 (beta) decode a JT-65 signal at 183Hz on Nov >>> 7, 2014: >>> >>> 1607 -23 -0.5 183 # UK8OAR DG5SAY R-20 >>> >>> 1609 -22 -0.5 183 # UK8OAR DG5SAY 73 >>> >>> 73 >>> >>> Paul DU2/WA8UGN >>> >>> -------------------------------------------------------------------------- >> ---- >> Follow-up information: >> >> Date/Time: 11/7/2014 1607-1609 UTC >> Frequency: 14.076183MHz >> Low-end audio cutoff (-3dB): ~300Hz >> Low-end audio cutoff (total: ~120Hz >> Equipment: Kenwood TS-570D >> SignaLink USB Sound Card >> Sony VAIO VPCCB laptop >> >> Cheers & 73, >> >> Paul DU2/WA8UGN (formerly G5BNV) > > ------------------------------------------------------------------------------ > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
