From: spam@spam.com   
      
   On Mon, 18 Jul 2011 16:20:55 -0500, John Byrns    
   wrote:   
      
   >In article <4e2454b7.207434@news.eternal-september.org>,   
   > spam@spam.com (Don Pearce) wrote:   
   >   
   >> On Sun, 17 Jul 2011 17:06:09 -0500, John Byrns    
   >> wrote:   
   >>   
   >> >In article <4e22c684.16025155@news.eternal-september.org>,   
   >> > spam@spam.com (Don Pearce) wrote:   
   >> >   
   >> >> On Sun, 17 Jul 2011 04:14:48 -0700 (PDT), Patrick Turner   
   >> >>  wrote:   
   >> >>   
   >> >> >I tried full wave, but not so easy at all. I've tried a 2 diode   
   >> >> >voltage doubler, also not worth the slight increase in Vo.   
   >> >> >   
   >> >> >There is utterly no need for any more than what I have, IMHO.   
   >> >>   
   >> >> Have you tried a synchronous detector? Generate a well-limited square   
   >> >> wave at the IF frequency and use it to switch a full wave diode   
   >> >> bridge. This will recover - with perfect linearity - any AM signal,   
   >> >> even one modulated well beyond 100% (provided it has been carried out   
   >> >> properly).   
   >> >   
   >> >Neglecting the problems with the limiter around the zero carrier point,   
   your   
   >> >scheme doesn't work for signals "modulated well beyond 100%" in the   
   negative   
   >> >direction.  The problem is that when modulation exceeds 100% in the   
   negative   
   >> >direction the phase of the carrier flips causing the switching of the diode   
   >> >bridge to be out of phase with the original carrier, causing serious   
   >> >distortion   
   >> >in the receiver.   
   >>   
   >> That is precisely the circumstance in which the synchronous detector   
   >> scores. Over-100% modulation is recovered correctly. With a simply   
   >> diode detector, of course, it simply clips.   
   >   
   >No, you are completely wrong here!  First with negative modulation greater   
   than   
   >100% a diode doesn't "simply clip", what it does, assuming a perfect diode   
   >detector, is recover the envelope of the modulated waveform.  What happens   
   >assuming a sine wave test signal, is that the portion of the signal that   
   exceeds   
   >100% negative modulation flips upside down as seen by an envelope detector.   
   >   
   Quite so, my bad.   
      
   >Second what you are describing is what I believe is called a pseudo   
   synchronous   
   >detector.  This type of detector responds in a similar manner as the diode   
   >detector does, although for slightly different reasons.   
   >   
      
   No, what I am describing is an entirely synchronous detector - maybe I   
   described it poorly.   
      
   d   
      
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