[time-nuts] crunching numbers from XOR phase detector

Joe Gwinn joegwinn at comcast.net
Wed Jan 4 11:14:47 EST 2012

At 10:16 AM +0000 1/4/12, time-nuts-request at febo.com wrote:
>Date: Wed, 04 Jan 2012 00:58:24 -0800
>From: Hal Murray <hmurray at megapathdsl.net>
>To: Discussion of precise time and frequency measurement
>	<time-nuts at febo.com>
>Subject: Re: [time-nuts] crunching numbers from XOR phase detector
>	<20120104085824.8426E800037 at ip-64-139-1-69.sjc.megapath.net>
>Content-Type: text/plain; charset=us-ascii
>Neat.  Thanks for sharing.
>With a XOR, you can't tell which input is higher frequency.  I think you can
>fix that with a second XOR and a delay line.
>I think 90 degrees of delay will provide the most information.  At 10 MHz,
>that's 25 ns.  I think that's about 15 feet of good coax.

Beware of teflon dielectric cable, as the teflon knee is centered 
around room temperature, making delay cables of teflon quite 
sensitive to slight changes in temperature.


Joe Gwinn

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