I agree this is something amateur equipment manufacturers like Elecraft should be keeping their eye on. If Analog Devices or someone came out with an under-$100 ADC with performance close to the K3, then you could save a lot of money and complexity by going to a directly-sampled RF front end architecture.
But a lot of brilliant engineers have been working for many years trying to optimize ADC design. I just really have my doubts that they are going to make a 15-20 dB breakthrough any time soon. Al N1AL On Tue, 2009-02-24 at 09:55, Larry Phipps wrote: > Not today... but give it a couple years. There is a lot of R&D being > poured into this by a number of competing chip manufacturers. Even if > the next batch of designs falls a little short, an all digital design > with BDR close to the best conventional designs would probably enjoy a > very substantial market. > > 73, > Larry N8LP > > > > Alan Bloom wrote: > > 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
