[time-nuts] crunching numbers from XOR phase detector

[David]

On Wed, 04 Jan 2012 00:58:24 -0800, Hal Murray
<hmurray at megapathdsl.net> wrote:

>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.

I was thinking of an added D flip-flop, D latch, or a 330 ohm 100 pF
RC delay in front of a second XOR gate.