On Mar 5, 2009, at 3/5 5:26 AM, Igor Sokolov wrote: > Bob, does it mean that the USB sound card built into MicrokeyerII > cannot be > utilized by LP-PAN? Why?
Not that you cannot use just any garden variety sound cards, but there are at least two reasons to use a better sound card with an SDR. The dynamic range of the simple sound cards will be a limiting factor when used with something like the LP-PAN. Although the digiKeyer and microKeyer II have relatively low noise floors for a 16 bit codec, it is still a reason to use better sound cards for an SDR. I had measured the distance between the noise floor and the full scale of the sound cards in both the microHAM keyers to be in the 95 dB region. You have an extra 10 dB or so of headroom with a sound card like the EMU 0202 (USB) or Edirol FA-66 (FireWire). For an SDR type use, the harmonic distortion from sound cards also factors into your choice. If needed, you can move the harmonics of a strong station from clobbering a weak station by turning the VFO knob on the K3 -- it is just inconvenient to do so. A second big factor that influences the choice of sound cards for an SDR is the highest sampling rate they can operate at, since that determines the width of the "panorama" which you can see. The highest sampling rate from the microKeyer II is 48,000 samples per second which, when used in a quadrature fashion, limits the "panorama" to about 40 kHz. Both the EMU 0202 and the Edirol FA-66 can go up to 192 kilo samples/second. 73 Chen, W7AY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
