<QUOTE> The real interesting question here is: how important is this in real life? Both interfaces work fine doing everyday PSK31, RTTY, SSTV etc, but how critical does it become when working signals near the detection limit as in WSJT JT65, FSK441 and very weak HF PSK31? </QUOTE>
This is something I've been thinking about for a long time. Remember that we use the sound card as an A/D converter. Thus the overall frequency response beyond whatever is necessary to digitize the desired bandwidth is at best unused, and at worst capable of creating spurious signals in within our band of interest. It MIGHT be that a soundcard with limited bandwidth might be BETTER for our needs. Now, in terms of S/N ratio... I find it hard to believe that quieter isn't better no matter how you look at it. Peter K1PGV
