I've done some experiments like this with a Ten Tec Corsair II. I used a Time Machine board from Expanded Spectrum Systems as the I/Q "mixer" for the IF stage. Other than some mild distortion to the RX audio that I attributed to DC coupling between the Corsair and TM board (noise currents flowing on the outside of the IF coax lead) and/or a impedance mismatch (between the TM board's input and the Corsairs filter output) it worked very well. I tapped into a point of the RX signal path immediately after the 9MHz 1st IF filter of the Corsair with just a small cap. This point in the Corsair's RX signal path does not yet have any AGC applied to it since the AGC in the Corsair is applied entirely within the IF chain, specifically the 6MHz and later IF stages. So in these experiments the AGC was being handled completely within the software I ran.
In the case of these other receivers mentioned in this thread you may want to choose a point closest to the first IF as you can to keep the amount of phase noise and other mixer stage generated "bad stuff" from being fed to the I/Q mixer. The other neat thing about the Time Machine board is that it can be used as the basis for modifying a radio to have DSP IF on TX as well since it has both RX and TX quadrature mixers. Even with these two sets of mixers the board itself is not terribly expensive. The Time Machine board worked fine with both SDRadio and PowerSDR just fine. Have not yet tried it with Rocky but I'm sure that it will work well there too. I was playing with the RX side of this about a year ago but haven't done anything more with it since last spring. Too many projects and not enough ambition ;). Duane N9DG > Subject: New User > > Hello all, > > I discovered SDRadio.exe, and I'm planning to make a > quadrature > detector for the IF of my KWM-2A. Just for the heck of it, > I decided > to run the program anyway without a "Q" signal. I have to > say that > this is good stuff! Finally, I have bandpass tuning as > well as > bandwidth tuning. Now, if it had one or more notch > filters, I'd be in > heaven. And, that's WITHOUT haven an actual quadrature > detector in > the picture! > > I'm planning to use something similar to KK7B's Binaural > I-Q Receiver, > but using the BFO from my KWM-2 for the oscillator, and > changing T1, > C47, and C48 as appropriate for 455kHz. If anyone's > already gone down > this road, I'd really appreciate hearing about it! > > My thanks to Alberto for some really useful software! > > Bob - AE6RV __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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/
