Tayloe, Asbrink, and Youngblood have all understood how difficult this is to use and get good performance. As such the Tayloe's unbalanced or the Asbrink/Youngblood balanced designs get us nearly there with large dynamic range and extremely good linearity. These circuits are sample and hold circuits. With some attention to detail, this is all we need and it will be much easier to attend to than dealing with 100 msps 16 bit A/D's. The recent ARRL review (to be published in the October issue) show that the recently modified SDR-1000 front end has the best dynamic range at 2 kHz of ANY receiver ever measured by the ARRL or the Sherwood site or anywhere else that I can find for that matter. The SDR-1000 2 kHz dynamic range is as good as the Elecraft K2, IC 7800, and Orion 20 Khz dynamic range numbers!
I believe strongly that these simple circuits make these high speed A/D's unnecessary for narrow band applications where narrow band means up to 100 kHz (!) for frequencies up to 6 meters and maybe beyond. Given this, the thing to do in my opinion, is to figure out how to push these clock generation spurs down and to push the high speed A/D's well into the background for the foreseeable future unless we need close to MHz wide signalling. http://www.flex-radio.com/articles_files/2005-10_QST_Review.pdf Bob N4HY i2phd wrote: >The ideal SDR has the antenna directly connected to the ADC, and from >there on all is done is software. We are not quite at that point yet, >bit this new ADC from Analog Devices is a step in that direction... > >http://www.responses.com/emw/380/9446.html?c=63r9t > >Its dynamic range (80 - 85 db of SFDR) is not enough to allow the >above, but could be useable, at least at an experimentation level, >preceding the ADC with an AGC-controlled front end (with all the >disadvantages that such a solution implies...) > >73 Alberto I2PHD > > > > > > >Yahoo! Groups Links > > > > > > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
