Juan EA7FNJ wrote: > Hi guys, I have seen some schematics and I've got a question: > > At the input of SB, do I put a IF freq about 25KHz? If the SB is about > 48KHz, I get the IF and they change into a two signals I & Q about 25KHz. > > 455KHz - 1720 KHz (LO 4x) = 25KHz I & Q > > Is it correct? I hope I don't miss on this.
Juan, basically it is correct, with some caveats. Your LO is 1720 kHz, which divided by 4 (if you use a Johnson counter) gives 430 kHz. You must produce 4 phases at 430 kHz, spaced 90 degrees from each other, which are sent to a quadrature mixer, which will give as output the I and the Q components of the difference frequency, i.e. 455 - 430 = 25 kHz. Then you send these I and Q components to the sound card for digitization. The software will then bring that 25 kHz IF down to 0 Hz (DC), and extract the lower or the upper side band. 73 Alberto I2PHD ------------------------ 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/
