mulveyraa2 wrote: > I am surprised at how many digital ops seem to run rigs without IF > filters - even on rigs that can accomodate them. It seems like > everyone wants to see the entire 2.8khz passband at once, even while > in a QSO. It makes far more sense to use the whole passband when > you're looking for a QSO, and then cranking in the IF filter once > you've established a contact. I use MixW, for example, and have a > macro that will instantly center the signal I'm looking for in the > middle of the passband, and then engage the 270hz filter. When I'm > done with the QSO, another macro opens it up again. I presume most > other digital soundcard software permits the same functionality. > > - Rich
Exactly right. Using MixW, when I am tuning the band I will have my rig's 2.4Khz filter engaged, so that my waterfall shows a fair chunk of the band. But once establishing contact or calling a station, I use the ALIGN macro to center the other station's signal in the rig's passband (1000hz for the 1KMP/MkV) and engage the 250 hz filters. As Skip says, this is not proof against a signal that is right next to the one you are trying to copy. It does, however, very much protect against desensitization caused by signals say, 150hz or so to one side of it. Additionally, IF Shift and IF Width controls can often take out signals that are inside the 250hz bandwidth "corridor" that the filter provides. That is one reason that good IF Shift controls are so valuable when running digital. It may be worth noting that an MFSK16 or Olivia (500hz) or MT-63 (500hz) signal fits very nicely within the corridor that a 500hz filter provides. Often, no usually, the protection of a good IF filter provides the margin between marginal copy subject to interference, and Q5 copy. de Roger W6VZV
