--- Kevin der Kinderen <[EMAIL PROTECTED]> wrote: > I'm geeking here, so don't say I'm wasting my time. > I already know that. ;-) > > How much does the quality of the soundcard affect > the quality of the > transmitted (or even received) signal?
Sampling clock frequency may be critical with cheap cards under Windows. > Are the > current modes (PSK, > MFSK, RTTY) not so critical that the differences > between soundcards > are "below the noise level?" Depends on the quality of the sound blaster chipset... > On PSK I have been playing with various settings of > DIG GAIN (FT- > 897D) and audio out from the sound card to find the > best IMD as read > on my KK7UQ meter. The best I can get is -30 dB IMD > by having most of > the controls near the mid-range. That is usually the best that linear power amplifiers perform "in the real world" in ham rigs. Some pro stuff might fare a bit better, down to -40 dB IMD, but those radios are rare among hams and expensive. > If I max out the audio from the > computer and back down the DIG GAIN to compensate, > my best IMD drops to maybe -25 dB. This leads me to > believe the soundboard quality can make a difference. Yes, it all adds up... > I'm considering an M-Audio soundcard to play around > with and see what > differences that might make. The model I'm looking > at is 2496 > (getting a great price used). > > Is there a method of measuring IMD at the soundcard > before it even > reaches the radio? Does that spec even apply at that > level? You could, but the worst offenders are usually the higher level stages, the power amplifiers. > The specs that seem to make a difference are: > 24-bit/96KHz > Freq Response: 22Hz-22KHz, -0.4, +/-0.4dB > Dynamic Range: 104dB (D/A) 100.4dB (A/D) > THD: <0.002% > > The specs I found online for my current Ensoniq PCI > (Soundblaster) > card are: > 16-bit/48KHz > Freq Response: 50Hz-15KHz +/-0.1dB > Dynamic Range: 81.3dB to 79.5dB > THD: .006% to .018% > > Again, just geeking. But definitely would be > interested in hearing > from others that might have contemplated this issue. > > 73 de KJ4QF > Kevin Good luck. Will be watching for comments on the list... Jose, CO2JA ____________________________________________________ Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs The K3UK DIGITAL MODES SPOTTING CLUSTER AT telnet://208.15.25.196/ More info at http:///www.obriensweb.com Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/