If you throw attenuation at the signal and the issue goes away, the cause is most likely on the receive side. It also helps to have a panadapter available (something that isn't tied into the AF chain). The waterfall itself should not be used to determine signal quality.
73, Jim S. N2ADV > On Jul 11, 2017, at 2:45 PM, Bill Somerville <g4...@classdesign.com> wrote: > >> On 11/07/2017 19:12, Tim Carlson wrote: >> Would you consider that the first signal on the left is being overdriven >> somewhat? Or is that just a consequence of a stronger signal? Or is it >> some atmospheric condition causing the signal to spread? >> > Hi Tim, > > hard to tell but it is all too common for the Tx audio level fed to the rig > to be too high. This causes non-linearity and will almost certainly widen the > transmitted signal. The main product of clipping is harmonics but if the > sender is using the split operating facility that is largely innocuous due to > the harmonics being above 3000 Hz and attenuated by the rig's Tx SSB filter > low pass cut off. Still there is no excuse for over driving the audio input > to the rig and there is a secondary consequence. At each frequency shift of > the modulation there is a minimal phase discontinuity, we shift the phase > without a glitch but nevertheless it is a discontinuity. These small > discontinuities fractionally widen the signal when the audio is correctly > matched through to the transmitter but over drive widens them considerably. > This is what you are seeing, a horizontal spike on the waterfall at each tone > shift. > > You must also be careful about attributing blame in these situations, all of > the above can happen on the receiving side too, so check your own house is in > order before accusing another of having a poor signal. > > 73 > Bill > G4WJS. > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
