[hpsdr] Phase detectors

[FRANCIS CARCIA]

Somewhere in the shack junk yard basement I have a couple AD9901 samples of a dual mode phase detector. It pulls the VCO to lock with the standard Flip Flop configuration then changes over to an XOR. I think our Russian Member did the same thing in his great QEX article inside the FPGA. I'm not sure if A.D. still makes the part but it sure sounds like it solves the close in phase noise problem. Also when you are using a oscillator with a limited tuning range like a SAW VCSO I would think the XOR phase detector could handle the job.
  At Andersen we had a homebrew set up to measure close in or very low phase noise using a DBM as a phase detector. This is a common test method even in the HP8640B service manual. Frank   
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