[time-nuts] Generating a solid PPS from 10Mhz source

John Ackermann N8UR jra at febo.com
Wed Jan 13 08:25:15 EST 2016


Tom Van Baak has developed dividers based on simple PIC chips that will 
produce 1 PPS from several input frequencies.  These dividers have 
remarkably low jitter, down in the couple-of-picosecond range, and are 
very simple.

I've implemented life support circuitry around two versions of Tom's 
code, both available as kits from TAPR:

The TADD-2 is a 4x6 inch board with 6 BNC outputs, each of which can be 
set to provide 1, 10, 100, 1K, or 10K PPS from either a 5 or 10 MHz input:
http://tapr.org/kits_tadd-2.html

The T2-Mini is a tiny board with a single input and output.  The default 
firmware allows PPS output for 1, 2.5, 5, or 10MHz input:
http://tapr.org/kits_t2-mini.html

Both of these devices have a low-jitter sine-to-square converter on the 
input, and work over a wide input amplitude range, so just about any 
sine wave will drive them.

John
----

On 1/13/2016 4:22 AM, Jerome Blaha wrote:
> Hey Guys,
>
> Is there an easy circuit to build that can consistently deliver a 1 PPS from a 10MHz source with excellent resolution and repeatability?  My first application is to test different 10MHz oscillators without a TIC always attached and then compare the PPS output change over time against a master GPSDO PPS with an HP53132A.
>
> The circuit used for PPS generation would have to deliver consistent PPS output with preferably not more than 100ps noise or jitter, assuming a perfect source.  I'm totally guessing that for this resolution, the PPS would have to be generated and accurate to within 0.001Hz every second.  If this is too difficult, maybe the integration time can be increased to generate one pulse every 10second or every 100,000,000.00 cycles?
>
> Finally, is a square 10Mhz reference any better in this case than a sinusoidal input for generating the PPS?
>
> Thanks,
> Jerome
>
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