Dave wrote: > > Has anyone tried using either a 250 Hz or 500 Hz filter for PSK31 > reception? My Icom IC-746 (non-Pro) has no filters installed, and is > wide as a barn door on USB for PSK31. I wondered if either of these > filters would help, or would they be too narrow? > > The pass-band shift does a fair job of eliminating QRM from one side > or the other of the selected frequency, but when there are two very > strong signals within 2 Khz on each side at the same time, they just > aren't effective on both. > > Any input appreciated! > > Thanks in advance es 73 Dave KB3MOW
ABSOLUTELY! My FT-1000MP/Mark V has both dual 500hz and dual 250hz filters, and I **always** use them in the course of a digital qso. For PSK31 and Hellscreiber, the 250hz filters are often, no usually, the difference between Q5 copy and no copy. For Olivia (500hz) and MFSK, the 500 hz filters are equally essential. The key is to ensure that you align the passband such that the signal that you are listening to is in the center of the receiver's passband. (You can do this with the <ALIGN:(passband center freq)> macro in MixW, or the Center command in PSK31). Then kick in the filters, and often you will be astounded at the difference in the quality of the copy. Listening wide open is fine when you are looking for someone to work. But once you establish contact, the filters are essential in our crowded digital mode bands. I cannot tell you how many times I have saved a QSO this way from PacTrash, or just other digital op signals. de Roger W6VZV
