Juan: The answer is, at is always is, it depends. Are you building an HF receiver/transmitter/transceiver? It is extremely difficult to get A/D's with sufficient dynamic range, good linearity numbers, and good noise floor to operate at reasonable IF's. If you want to think of this way the QSD and Tayloe are both sample and hold circuits but with outstanding numbers for dynamic range, linearity and noise floor. It will be pretty hard for you to beat the 10.7 MHz IF you build out of a QSD mixer.
Then you begin to study the problem even more closely. And you find that it is really hard to build RF amps and mixers and IF amps in front of the QSD that do not seriously hamper the performance. Read the receiver performance numbers for the NC2030 or the ARRL measured numbers for the QSD in the SDR-1000 http://www.flex-radio.com/articles_files/2005-10_QST_Review.pdf and you see that it is really hard to see how you can beat just doing the QSD and doing ADC/DSP at near audio. N8BV, Phil Covington has published a very interesting variant. It has some unique attributes. It is not the QSD (balanced) or the Tayloe (unbalanced). It does not use sampling capacitors but active LPF's and virtual ground: http://pcovington.blogspot.com/ He is doing several very interesting things and has done some great stuff for the PowerSDR project as well. It is absolutely amazing to me how much there is yet to learn in this fascinating area. Bob N4HY Juan EA7FNJ wrote: >Hi guys. > >I have a question: > >What is the best way: > >- Input the IF signal to a ADC and make all the process by DSP > > or > >- Input the I/Q signal from the Tayloe Mixer to a ADC and DSP > >??? > >At te begin of this summer, I made a USB Modulator by a DSP TMS320C >because it was a little project of my career. What is the best way in >a SDR? > >73 > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > -- Laziness is the number one inspiration for ingenuity. Guilty as charged! ------------------------ 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/
