The dynamic range of the SDR-1000 equals the dynamic range of the A/D converters and in the case of a stock unmodified Delta 44 it's 99db .... raise the dynamic range of the A/D converters and you also increase the dynamic range of the SDR-100 .. the dynamic range of the front end is actually higher than that, there just aren't any commonly available/reasonably priced soundcards that can take advantage of it
There seems to be no limitation at 99db from the DDS in the SDR-1000 and it's only using a 9854 .... it stands to reason the one you are talking about is actually overkill until the A/D converter end of the system is expanded John --- In [email protected], Nick Whyborn <[EMAIL PROTECTED]> wrote: > > I'm two months late with my comment but... > > I don't think the AD9446 is as bad as Alberto made out. According to the > features list it is capable of 100dB 2-tone 3rd order SFDR, though there > are no details or figures in the preliminary datasheet to support this > claim. The SNR or ENOB of the device will not be a limitation in the few > kHz bandwidth of the final filter since there will be a processing gain > of > 30dB. > > On the other hand the performance quoted in the SDR-1000 review is not > exceptional if the 2-tone 3rd order IMD dynamic range is only 97-99dB > with a 500Hz filter bandwidth. Restating that to the normal 2.5kHz > bandwidth gives a dynamic range of 93dB. However, the fact that it is > that good to within 2kHz of the 500Hz filter is impressive. > > The review indicates that the DR is flat beyond 2kHz which struck me as > surprising. I would have expected that beyond 100kHz or so the LPF on > the output of the QSD would shield the sound card from strong signals > and the QSD itself or the preamps would become the limiting factor. > > Of course, I'd have to agree with Bob's comment that it is far easier to > get the direct conversion + audio SDR approach to work (well) than the > high speed A/D + DDC. > > Nick, > G4JNX. > > Robert McGwier wrote: > > >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 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/
