After a user reported problems with filter settings in N1MM+ in SO2V with one VFO in CW and the other VFO in SSB, I did some investigating. I had never tried mixed-mode dual receive before. After doing some experimenting, first with N1MM+ and then with the radio on its own, I conclude that there does appear to be a problem, but it seems to be in the K3 firmware, not in N1MM+.
After some initial exploration, I ran audio spectrum analysis software on the Line Out output of the K3 with band noise input on a dead band, default filter settings and with no radio control software of any kind running. With both VFOs in SSB, the noise spectrum display is similar for both VFOs - reasonably flat (plus or minus a few dB) from 200 Hz to 2800 Hz, more or less. If one VFO is in CW and the other VFO is in SSB (or DATA A, which seems to behave the same way), the VFO A SSB plot looks the same as before, but when I use the K3's A/B button to swap VFOs, the spectrum display for VFO B in SSB looks quite different, with a more or less linear rolloff of roughly 10 dB/kHz (not per octave, per kHz) from 700 Hz to 2700 Hz. That is, at 1700 Hz the spectrum plot is down around 10 dB from the value at 700 Hz, and at 2700 Hz it is down around another 10 dB. The difference is clearly audible. I can fix this by pressing the B-SET button on the K3, which restores a flat response profile in VFO B, but when I press A/B twice to swap the SSB and CW settings between the two VFOs twice, the rolloff comes back when VFO B is in SSB mode. Has anyone else seen anything like this? Is there a configuration setting that can fix it? 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 Message delivered to arch...@mail-archive.com
