[time-nuts] 5 MHZ PIC PPS Divider?

John Ackermann N8UR jra at febo.com
Sat Apr 12 10:44:06 EDT 2008

Thanks, Bruce.  I considered the idea of a multiplier but would like to
use a software-only solution if I can.  That's not only for simplicity,
but also to eliminate additional sources of jitter; the experiment I
have in mind is to test the second-to-second noise (and short term noise
trends) of GPS and other PPS sources,* so I'm looking for as stable a
reference as I can get.  The additional noise from a mulitplier may be
small, but I want to minimize the number of unknowns.



* I realize that I'll also be limited by counter resolution.
Bruce Griffiths said the following on 04/11/2008 05:56 PM:
> John Ackermann N8UR wrote:
>> Has anyone come up with a 5 MHz input version of TVB's PIC divider?  I
>> could use one...
>> Thanks,
>> John
> John
> You could always cheat using a simple frequency doubler.
> Use a pair of diodes to create a fullwave rectified sinewave followed by 
> a comparator for a sinewave input.
> A simple feedback loop can be used to ensure the comparator output duty 
> cycle is 50%.
> Use a circuit that generates a pulse on every transition for a square 
> wave input.
> Low pass filtering the square wave can be used to produce a waveform 
> that the comparator above could work with.
> A feedback loop could be used to maintain the comparator output duty 
> cycle at 50%.

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