The Elecraft K2, undeniably a highly rated transceiver, uses a 602 as the product detector **after** the IF ... I have a self designed receiver that uses a 602 in a similar circuit ... The ARRL Handbook used to have a AM Sync detector circuit that used a pair of 602's (As well as a 604)in a similar circuit to what he is using
If a 602/612 can be used successfully as product detector/demodulator after an IF then it can easily be adapted for use as a quadrature detector after an IF If you have ever put the unfiltered output of a 1st mixer on a spectrum analyzer you'd understand that using the 602 in the same place is going to be real messy without some decent filtering in front of it JR --- In [email protected], Cecil KD5NWA <[EMAIL PROTECTED]> wrote: > > On Wed, 2006-09-13 at 01:51 +0000, jr_dakota wrote: > > --- In [email protected], Cecilio Bayona <KD5NWA@> wrote: > > > > > > Ray Anderson wrote: > > > > Dan- > > > > > > > > > > > > > > > > I missed the earlier part of this thread, but can you explain > > what the > > > > SA612 has to do with a QSD (quadrature sampling detector). The SA612 > > > > mixer is a double balanced Gilbert cell type circuit. No sampling is > > > > involved. > > > > > > > > > > > > > > > > -Ray WB6TPU > > > > > > > > > > > > > > > ka9rza <wavelengths@ <mailto:wavelengths%40netzero.net> > > > > > > > You can integrate the outputs of any kind of mixer, and by using two > > fed > > > by a LO in Quadrature generate I/Q audio. The SA612A's have a > > conversion > > > gain so they make for a sensitive mixer. > > > > > > FET switches are not only highly efficient but have an extremely high > > > IP3 compared to SA612A's > > > > > > Switches are far cheaper also, personally I'll stick with the switches > > > unless going really high in frequency, > > > > > > > > > Cecil > > > KD5NWA > > > > What you say is true in the case of direct conversion but what he's > > doing is taking an IF signal from an existing receiver and splitting > > it into quadrature ... since the output of an IF has a small dynamic > > range because of the AGC the 602/612 are good for this (In fact they > > are designed to use after the IF), especially for people who don't > > want to fiddle with SMT IC's ... also since the oscillator frequency > > will be fixed, getting your quadrature at oscillator will take a > > fairly simply LC network instead of higher frequency oscillator and a > > divider network > > > > The downside is his IF filter will set his maximum bandwidth in > > SDRadio or any othr SDR software he uses, so he doesn't get to see a > > 48Khz chunk of spectrum, only the 4-6Khz bandwidth of his IF filter > > > > JR > > > The output of the IF of a lot of receivers by the time you get to the > narrow filters is quite high, more than what that chip is designed to > handle, you would be better of picking up the signal after the first > mixer, long before the narrow filters and all that high gain that will > overload that chip. > -- > > Cecil > KD5NWA > www.qrpradio.com www.hpsdr.com > > "Sacred Cows make the best Hamburger!" Don Seglio Batuna > 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/
