The circuit is simple, just use a standard opamp diffential amp arrangement ... you could probably drop a 5532 into this circuit in place of the LT6231 and make it work ... you'll just need a higher supply voltage
http://www.norcalqrp.org/files/AustinNC2030Presentation.pdf The schematic is several pages into the presentation but reading the entire thing wouldn't hurt anyways since it's written by Dan Tayloe himself They guys doing an IQ radio in all hardware should take a gander at this also, even though it's a single band radio and is only uses 3.3V and draws 11 ma, it outperforms about everything on the market and should be easy to adapt to 100khz to 30Mhz using AA0ZZ's IQ DDS This looks to me to be one of the most signicant pieces on direct conversion receivers since Rick Campbell introduced the world to his R2 receiver ... In fact I'm toying with the idea of buying the kit and adapting it to Craig's new IQ Pro when it comes out and using it for both hardware and SDR software decoding Another circuit you can use that will work as well and probably better than an INA amp (They have an inherent noise problem with gains below 40db) is this one http://sound.westhost.com/project66.htm It will work with lower gains and stay quieter and uses common parts, you can substitute a 2N4401 for the BC549 with no noticable difference, I'd stick with the TL072 since it's got an input of 22k ohms ... a rule of thumb, for 10k and below inputs use a bipolar input like the 5532 (low voltage noise), above 10K the FET inputs (Low current noise)like the TL07x series are a better choice John --- In [email protected], Paolo Cravero as2594 <[EMAIL PROTECTED]> wrote: > Hi, > I remember seeing a QSD circuit using a couple of NE5532 instead of more > expensive INA111 & C. > > Unfortunately I can't locate the diagram, if it actually exists. > > Can anyone help me? Thanks, > Paolo IK1ZYW > > -- > | QRPp-I #707 + www.paolocravero.tk + I QRP #476 | > \ Italian/English-to/from-Croatian translations / > \ Skype: pcravero / ------------------------ 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/
