I played with line out settings today to determine for my soundcard-K3 setup what an optimum line out setting might be. I think of optimum as that setting that produces adequate speckling on a waterfall display with minimum harmonic distortion.
My K3 serial 508 has all of the audio modifications that I am aware of. I can remember conducting a study like this prior to modifications unfortunately I can not find my old data. Bottom line I have my line out set at 3 now. This gives good copy on PSK signals, good speckling on a waterfall and maximum signal-to-3rd-harmonic ratio. Spot pitch = 500, CW signal centered, 3rd harmonic well outside of roofing filter as well as 50 Hz IF filter. The only way for the 3rd harmonic to be seen is if it is created in the analog post digital audio stages. For PSK copy I would be using wider filters but much wider would mask the 3rd harmonic measurements which I wanted to be well beyond the processing pass band. Using Spectrogram for signal measurement and Ham Radio Deluxe-Digital Master 780 for PSK copy I took some data below. At line out set at 3 I found maximum base signal to 3rd harmonic ratio. I find this is pretty good at the lower line out settings and up to 15 dB worse at significantly higher settings. I would guess that most could live with the higher settings if the sound card needs it. IF BW = 50 Hz Roofing Filter BW = 500 Hz Line Reference 3rd Delta Out dB Harmonic 3rd 0 -68.6 noise limited 1 -55 noise limited 2 -41.7 -113 71.3 3 -38.2 -111 72.8 4 -35.8 -107 71.2 5 -33.5 -101 67.5 10 -27.8 -87.5 59.7 15 -24.5 -82 57.5 20 -21.5 -80.3 58.8 25 -19.4 -78.5 59.1 30 -18.1 -75.8 57.7 50 -13.7 -72.1 58.4 100 -7.7 -67.8 60.1 Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) NAQCC 3535 K3-100 #508 / KX1 #1311 ______________________________________________________________ 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
