LF: Reasons for different soundcard sensitivity

[DL4YHF@aol.com]

Dear Jim and group,

The problem you mentioned (Jason decoding and waterfall sensitivity) may not only be a problem of the soundcard itself. Just a thought:

The reason can also be the computer itself: If windoze (or something else) occupies the CPU for too long, there may be an interrupted stream of input samples, producing a phase jump. 
To verify this, feed a clean and stable sine wave from an audio generator into the line input, and observe the signal on the waterfall (either Jason, Argo, SpecLab..). If samples get lost, the spectrum will get "broad" occasionally for a few lines on the waterfall display.

On my office-PC the inevitable microsoft-jingle is chopped into pieces when the system boots, despite a 1GHz-CPU. No trouble on an old 266 MHz-workhorse. I guess the DMA from harddisk and soundcard collide in some cases, in other cases they dont. Or one soundcard has a larger hardware buffer than others. Time to build external ADC hardware.. ?

Different SNR of the soundcards should'nt be the reason, as long at the input level is properly set. Or does one of the tested cards only have an 8-bit ADC ?

Regards,
  Wolf  DL4YHF.