It's not a question of needing more gain but a question of noise so you need to drive it with a preamp to overcome the noise and still maintain a low NF and decent MDS.... the 8333 has an IP3 of +30db but if you put a 10db preamp in front of it then you have an effective input IP3 of +20db (Still not too bad, just not nearly as good as the high speed buss switch QSDs)
If you have EMRFD look in the Mixer chapter (If I remember right) and you see an example of how this works using an NE602 with and without a preamp as an example One thing that popped into my head when seeing this IC is using it in a noise cancelling SDR configuration with one mixer for your main antenna and the other for a 'sense' antenna ... you'd need a 4 input soundcard like the Delta44 and as far as I know there isn't any software out there (yet) for this kind of application but a good programmer should be able to come up with something that would knock the socks off of any hardware solution JR --- In [email protected], "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > > JR > > Ok, you do not think there is enough gain and this needs a preamp and > thats undesirable. Noted. > > I am wondering if anyone knows of a place on the Internet that > carries info and files on the parameters of operation as well as > expectation for such things as the QSD? Most info is widely scattered. > I have the Tayloe circuits but no files of explaination but I suspect > now there are some somewheres. > > You brought up the matter of the noise figure and this looks to me to > be an important study to make. You learn one new thing and yet here > comes another. Maybe the ARRL will have a book if not by now. I know > they have the HPSDR project running and a radio ready for market. > > If this chip does not measure up then we have to go back to the > former chips we were looking at. The balanced mixer idea still looks > good. But these are free and will be something to do and learn about > this winter. > > The SBL-1 or TUF-1 seems very practicle in the circuits I have seen > and they do not need any front end pre amplification. There are more > ideas on the net with these chips than other chips. The Time Machine > circuit was perhaps the best one so far. > > Ok on trying the single ended input idea with a capacitor to ground. > > > > > _____________________________________________________________________ > 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/
