FT8 filter edge "noise"

Rich McCabe

So have always wondered what this is. If I have my DIGU filter set to 3khz I see noise at the edge of the filter (see arrows).  If I drag my filter out a little wider that disappears.

Larry _ NY8T

open your receive filter more, I run mine at 0 to  5K and that noise you see goes away.

Rich McCabe

Yes that is what I am doing but I do not like to run excessive filter width. Should not be there. Was just wondering why.

Larry _ NY8T

Maybe filter skirts, any radio I use for Ft-8 does the same thing if I don't open the receive band pass more than what i want to see on the wsjt-x waterfall.

Rich McCabe

OK good info Larry. Thanks

Tim - W4TME

It is the filter roll-off at the band edges.  The DIGx filters don't need to be brickwall on the edges so by doing this we reduce signal propagation delay (latency) through the receive filter.

Making the filter a little wider at the high end will not affect FT8 reception

Rich McCabe

More good info.  Thanks Mayor.

Patrick

One more thing to check is to go into wsjt-x config to advanced under miscellaneous see what receiver bandwidth is and set it to 3000 and your digiu to 3000.  I think the default is 2.5k in wsjt-x.  Also set the bin/pixel to what is best for your display. In my case it is 2. These 2 settings gets it all matched to 3k RX BW and no noise bar.