At 11:15 AM 9/21/2006, Eric Wachsmann wrote: >I have swept through the entire 192kHz both in panadapter mode (11kHz IF) >and in SPEC mode (0Hz IF) and there is no aliasing visible like the FireBox >pre firmware upgrade if that is what you're asking.
But what's the rolloff of the roofing/anti-aliasing filter in the Edirol? If you're sampling at 192kHz, and you put a 90 kHz signal into the Edirol, does it show up at full amplitude? What about at 100 kHz? > The image is as it >would be with any other card...mirrored around DC (which is at -11kHz in the >panadapter, and at 0Hz in SPEC mode). So all this really checks is the channel:channel match down low (at 11 kHz, in particular). So if there's a phase or amplitude mismatch at, say, 40 kHz in the Edirol, a signal that is at DDS freq+40k will also appear to be at DDS freq-40k. I suspect that as the use of multiple receivers gets popular, this will become a more important. With the conventional scheme, the DDS frequency is adjusted to keep the IF at around 11 kHz, so, the I/Q balance only needs to work over a fairly narrow band (say, from 6-16 kHz, which, in the context of a audio device with notional 20-20kHz bandwidth, isn't unreasonable). Jim, W6RMK _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
