I'd say it's a toss up as to which is best ... If you talk to someone who has a Coversion reciever **designed specifically for SDR** (Like the Pic-a-Star) they'll tell you putting a crystal filter before your ADC (or after your DAC in the case of transmitting) does a lot of good for strong close in signals .... with Direct Conversion you only get a dynamic range of your ADC (or soundcard) which limits you to 99db whether the interfering signal is 5 Khz away of 20 Khz away .... with a Conversion SDR (I prefer to call this a Hybrid Architecture) you can easily exceed 99db for interferring signals 20 Khz away while retaining your 99db at 5Khz (If the ADC between the two are equal) .... one experiment I have planned is to switch in different caps on a QSD to restrict the bandwidth to the ADC when needed for close in interferring signals .... seeing a full 96khz of bandwidth is a convenience and doesn't really add anything to performance, in fact it weakens the performance for close in signals ... I'm thinking caps for 48Khz cutoff, 5-6Khz cutoff for high fidelity AM and SSB, 3Khz cutoff for SSB and 1khz cutoff for CW (Note that your receive bandwidth will be twice your cutoff frequency of the QSD)
A huge disadvantage to Direct Conversion for SDR is you are basically limited to 10 Meters and below, at least with a QSD scheme based on fast bus switches (SDR-1000 and various Tayloe designs) although I believe a properly designed diode DBM setup can do as well as a QSD without the frequency limitations ... we'll see when I compare an R2-Pro with my SDR-1000 clone/test bed sometime late next month JR --- In [email protected], "Juan EA7FNJ" <[EMAIL PROTECTED]> wrote: > > Hi guys! > > The question is easy: Direct Conversion or double conversion. > > What the best way is: make a simple direct conversion or get the IF of > a double conversion receiver? > > I have seen more Direct than IF. > > 73 > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/soft_radio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> 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/
