If I recall correctly, the S/N calculation is made in WSJT-X based on a fixed value somewhere around 2.8 kHz. Applying a wider or narrower bandwidth to the decoder will provide numerically different values, but not affect decoding performance UNLESS the narrowed bandwidth had an incidental improvement in noise rejection, AGC capture, or some other condition.
It may look good on the screen. It may sound better to your ear, but the software doesn’t really care. George J Molnar Arlington, Virginia, USA KF2T - FM18lv > On Oct 19, 2018, at 11:14 AM, Black Michael via wsjt-devel > <[email protected]> wrote: > > A decrease of bandwidth by a factor of 6 will increase reported SNR by > approximately 16dB. > But that's just a matter of what noise reference you use...not any real > change in the signal level. > If you used signal peak instead of RMS the SNR reported would be really > low....it's all relative to the value chosen for N. > > You could just as well divide the signal level by some really small number > and have 100's of dBs shown....the signal never changed though. > > de Mike W9MDB > > > > On Friday, October 19, 2018, 9:58:10 AM CDT, DG2YCB, Uwe <[email protected]> > wrote: > > > Frank, seems indeed to work! Just tested during RX of station KG4HF with > bandwidth of either 3 kHz or 500 Hz. See the following S/N comparison. > Astonishing! > > > <image001.png> > > > 73 de Uwe, DG2YCB > > > Von: Frank Kirschner [mailto:[email protected]] > Gesendet: Freitag, 19. Oktober 2018 15:48 > An: WSJT software development > Betreff: [wsjt-devel] Improving S/N > > > One thing I haven't seen discussed on this reflector is improving the S/N by > narrowing the receiver bandwidth. It is no surprise that decreasing the > bandwidth received increases the S/N, by 10 to 15 dB, sometimes more. When I > see a station I want calling at -24 or so, I can narrow the BW and get solid > communications. This is very easy with the graphical presentation and digital > filtering of the Flex 6600, but with a little practice, could be done on any > modern receiver. > > > This means that, if we knew where the stations were calling at -30 or so, we > could focus on them and bring them up to the point of making contact. Since > you can't decode stations at that S/N, it would have to be done "out of > band." Is there any thought being given to setting up an FT8-only DX cluster > with exact frequencies? > > > What a fascinating hobby! > > > 73, > > Frank > > KF6E > > _______________________________________________ > wsjt-devel mailing list > [email protected] <mailto:[email protected]> > https://lists.sourceforge.net/lists/listinfo/wsjt-devel > <https://lists.sourceforge.net/lists/listinfo/wsjt-devel> > <image001.png>_______________________________________________ > wsjt-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wsjt-devel
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