You may be right, Al. I think the improvements may be incremental, and distributed among various aspects of the design, not just the ADC. For instance, ultra-low jitter clock sources, faster FPGAs with improved IP cores, etc. I think most hams would be thrilled with an improvement to 130dB BDR, along with getting rid of phase distortion, ringing and other anomalies in the xtal filters and other analog components. Unless you live near a shortwave broadcast station, or have a high power ham nearby on the same band, you're not likely to need 130dB BDR anyway. Even in those cases, having 200dB BDR probably wouldn't help unless there is a LOT of improvement in transmitter spurious emissions, distortion and phase noise.
The highest signals I have seen here, during Field Day when there were several stations operating within a few miles of me, were <120dB above the noise floor. Of course, it's very important not to use any more front end gain than necessary for the band/conditions. 73, Larry N8LP Alan Bloom wrote: > > 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 > > -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2381481.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
