On Mon, 2009-02-23 at 18:40, N8LP wrote: ... > I think the days of receivers with xtal filters are numbered. High speed > ADCs capable of 140dB dynamic range without xtal filtering are on the > horizon. A 20-bit ADC with enough processing gain would do it.
I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. >65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
