Yesterday, having not yet thought of a better way to do a meaningful real-world test on the sound card with what is available in the KazShack, I fired up the 80m softrock on the ASUS Xonar DX for a bit of putzing around.
Test condx:
Transmitting a cw signal(a string of dashes at about 18wpm) at 5w into a dummy load on separate radio, noting the SNR readings obtained by CW skimmer from the SoftRock center frequency(353395x) to its upper limit. With the xonar DX set to 192khz scan rate, the actual upper limit on the readings was 3629.60. SoftRock connected to normal antenna system, a NE facing K9AY with W7IUV pre-amp. In summary, a sound card test using the SoftRock system as input source.
fq….—-SNR(dB)
3534.5—-42
3543-3593-42-40
3603——37
3613——35
3623——32
3629.6—-36
After CW skimmer collected a bit of data, the SNR readings above 3600 improved to 37-39.
So the worst case for CW skimmer(as currently configured) using a Xonar DX is being 6db less sensitive at the upper edge of the 192khz bandwidth than it is at the center. That is actually a lot better than I expected for an audio device pressed into service outside normal audio ranges (and I already liked the Xonar DX).
My curiosity is now nagging me to run the same tests on all of the other in-shack cards more methodically at their maximum scan rates(mostly 96khz), and to find a lower level outside signal source. I’ll try to recruit a fellow in the near field who will better be able to generate a low level test signal.
But with the WX here improving, all of that might not happen for several months. 😉
engineer the possible….
73 de w4kaz
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