Hello Andy, >Is calibration really an issue of concern IF an application can enable a >re-calibration process ? If an application enables re->calibration, does >that only "hold" for that application or can it correct the soundcard for >other applications. Yes that holds the application. The process is just to measure the "real" sound card sampling speed (the "standard" being the PC clock which has a precision better than 0.02%) and to consider this measured speed in your application. There is no way to calibrate the sound card itself . You simply take it as it is...
For standard narrow digital modes (as PSK31), if your AF level is good (let's say around 50 %, but not critical), there is no important need to have a very good sound card. For wide digital mode (Packet, ALE, MT63-2000 Hz, 110A), it would be a problem if the amplitude vs AF frequency would be not flat at all (the sound card is not supposed to be a filter inside the telephone bandwith (300-3000 Hz)). For SdR the problem is completly different because you need a real good dynamic. With a basic sound card, having the 10th bit noisy is not important for digimodes, but it would be very bad for a SdR if the input signal is very low (your real dynamic being bad, even if it is supposed to sample on 16 bits). 73 Patrick ----- Original Message ----- From: "obrienaj" <andrewob...@gmail.com> To: <digitalradio@yahoogroups.com> Sent: Wednesday, September 23, 2009 1:01 AM Subject: [digitalradio] Understanding soundcard basics ? > From what I have read in the past, there is a difference between > inexpensive sound cards and the high quality ones. I recall past articles > that suggest the high quality ones can result in some very weak signals > being detectable in a waterfall, whereas cheap cards may not reproduce > the signal. However, as most of us know, even the cheap sound cards > effectively render the average ham signals, even quite weak ones. > > So, aside from the higher end ones rendering weak signals on a waterfall > better, what are measurable difference between a poor cheap one and a > really good top-of-the-line one ? Can someone explain this is plain > English? > > I am aware of the "calibration/timing" issue. Although that too does not > seem to make a huge difference with many digital modes. Of the numerous > digital modes I have tried over the years, PC-ALE and JT65A in WSJT have > been the most impacted by calibration issues. I have seen WSJT not decode > at all when timing of the soundcard is not correct. Do higher end sound > card have less problems with timing/calibration than cheap ones? > > Is calibration really an issue of concern IF an application can enable a > re-calibration process ? If an application enables re-calibration, does > that only "hold" for that application or can it correct the soundcard for > other applications. > > I raise these questions out of general interest, but also because of > recent WINMOR test where the poor performance has been blamed , in part, > on cheap sound cards or sound cards not dedicated to the application. I > don't know enough to argue the point, but my suspicion is that it is > really not that sound card related. > > Andy K3UK > > > > ------------------------------------ > > Announce your digital presence via our Interactive Sked Pages at > http://www.obriensweb.com/sked > > Recommended digital mode software: Winwarbler, FLDIGI, DM780, or Multipsk > Logging Software: DXKeeper or Ham Radio Deluxe. > > > > Yahoo! Groups Links > > > > >
