The input transformer is there just to isolate the input signal, it has nothing to do with the Quadrature generation. It isolates the input from the bridge which is biased at 1/2 VCC so we can get away with using a single power supply on the comparators and op-amps.
If you are talking on my schematic QSD2 you will see that I'm detecting the zero-crossing of the signal across each side of the bridge of the two RC networks. Both signals shifts with frequency but the difference stays at 90 degrees. Amazingly that relationship holds for several bands. I had a more refined version, but dumb me I thought I had a backup of the schematics at home and deleted them, then I discover later that I didn't have a copy. I will try to redo the work, but right now things are going very slow. Lately I've not not been feeling so good so I'm barely keeping up with just going to work. But things are improving, I've not had any irregular heartbeats since last Thursday that I could detect, so I'm beginning to feel a little better. In a week or two I'll get back to it recovering the schematics full time. I have a print out but I don't have the better LTSpice models that they use, so I'll have to recreate them again. The most advanced "QSD6" was a complete multi-band transceiver, that I was going to build. I wanted to run a few more careful simulations before I create PCB's and send them out. At 02:32 PM 4/11/2006, you wrote: >KD5NWA: > > The transformer seems simple enough, especially with a fixed > mixing frequency. I found it being used with a vfo for 40 meters > and it does look allot like a balun or transmission line > transformer. I got an email on a file to check out a twisted pair > idea here today. > > Also, there is way to split a signal off into two for I Q with a > resistor in one line, equal in resistance to either a capacitor or > inductors reactance in the other line. The reactance's phase shift > voltage and current by 90 degrees in the one line. It appear that > a single capacitor or coil in the other line will shift ther pahse > 90 degrees but only if the frequency of operatiuon is fixed or limited. > >Dan > > >_____________________________________________________________________ >Call Anyone, Anytime, Anywhere in the World - FREE! >Free Internet calling from NetZero Voice >Visit http://www.netzerovoice.com today! > > > > > >Yahoo! Groups Links > > > > Cecil Bayona KD5NWA www.qrpradio.com I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ... [Non-text portions of this message have been removed] 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/
