G4ILO wrote: > Brandon673 wrote: >> >> I would like to hear opinions and reasons for the best filter to use for >> operating PSK31 with the K3. >> > > You don't need anything more than the SSB filter.
I agree with Julian. Remember, it is the DSP that is responsible for signal filtering. You do not need narrow roofing filters to enable narrow DSP filtering - you can narrow the DSP filter down to 50 Hz even if the only roofing filter you have is 2.7 kHz wide. The job of the roofing filters is just to keep unwanted strong signals out of the IF bandpass to prevent gain pumping (desense) and IMD (splatter generated in the receiver) caused by those unwanted signals. Regarding DSP filter settings: Wide filter settings are useful to scan the band, for S&Ping, and for multiple signal decoding. Once you have picked a signal to work, or if you are calling CQ, narrow DSP filter settings can be helpful. You can put your DSP filter controls in SHIFT-WIDTH mode and use the two controls to focus on the desired frequency, or you can use an Align or Optimize feature in your software to center the desired signal at a chosen frequency so you only need to adjust the WIDTH control. As for gain pumping and inter-signal IMD: the likelihood that you are actually going to encounter a situation that requires a narrow roofing filter for PSK seems quite remote. Extremely strong PSK signals are not that common, PSK signals turn on and off only on time scales of several seconds, and PSK detection is not highly amplitude-sensitive, so both the likelihood and the effects of gain pumping and inter-signal IMD would appear to be much reduced compared to other modes. Bottom line: I'd suggest you base your decisions re roofing filters on your needs for other modes, not on PSK31. 73, Rich VE3KI ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
