So far if I understand my receiver it is direct conversion. I then can say that it blows me away when I compare it to other receivers I have here on the bench. The selectivity is as narrow as you want, there are no out of band images except below medium wave, but you do have images in the sound card but thats not a problem really. Alberto's softwares allow for skewing adjustments that minimize these sound card images.
You can get cross talk between two really strong adjacent stations but a loop antenna can notch one out. The loop antenna is a good thing to have when you are serious about the signal quality in terms of noise reduction and unwanted station nulling. 455 KHz single conversion will suffer images up at 910 kHz from strong stations there. A single conversion to 10.7 MHz would be better if you want to use a single conversion scheme. I see QSD kits for 10.7 MHz very usefull. I would like to see or try a single or dual conversion scheme. I am pretty sure this receiver is direct conversion here. I have a diagram of it and I will study it again. As long as it is working as it does then SDR direct conversion will be as good as any communications grade receiver going. Direct conversion is perfectly fine in experiencing it. Its high tech enough. Selectivity again is excellent. Spurs are the only problem. If the signal is however medium to strong then they walk over top of the spurs. Spurs in one side band can be notched or else select the other sideband when in AM mode. If in SSB mode, you have to notch them out. If your SRD software does not have a notch, then if you have another PC, run the audio there and use a DSP ware with a notch filter feature. If you have a commercial SDR receiver and note that in a certain band that it has fewer spurs than any other band, you might then build a convertor to convert a band to that band segment with the least spurs. And thus work that band you are serious about, and hence this is a reason for single or dual conversion. And in turn, where the receiver has the most spurs you can convert the incoming band to a segment with least spurs so you can still hear that band being previously blocked by spurs. In the software you can enter in the LO IN not for the actual LO IN but for the band you have now converted and still have the frequency readout on the software read the band you are working. Just do a offset calculation and then you can see the band you are on in the software. And the number of conversions do not solve all your spur problems. Only with a scheme for a single band can you minimize the spurs unless you build a convertor or band selector for all bands to convert them to the cleaner DDS segment band. And that would increase the complexity. 80 meters for me appears to have the least spurs. So if I needed I could convert a band to 80 and get a cleaner band segment. So direct conversion will surprise you. Selectivity is defined by the software. Dan _____________________________________________________________________ PrivatePhone - FREE telephone number & voicemail. A number so private, you can make it public. http://www.privatephone.com 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/
