[time-nuts] 1 pps Sync'ing

Tom Van Baak tvb at LeapSecond.com
Mon Jun 25 10:38:19 EDT 2018


Steve,

> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs
> to be aligned with the GPS 1 pps (UTC) to within 1 ns.

Two comments.

1) If you divide 100 MHz -> 10 MHz -> 1 Hz then (with careful design, calibrated layout / wiring) you can have all three rising edges within 1 ns *of each other*. I assume this is your goal. If you already have a 100 MHz GPSDO then it would surprise me if the outputs are not already synchronized with each other. I mean, almost all GPSDO give a 1PPS output that is derived from the LO, by design. If your goal is 1 ns, you obviously do not want to use the raw 1PPS from the receiver. What make/model GPSDO are you using?

2) On the other hand, if your goal is that all the outputs are within 1 ns *of UTC*, then you have a big problem. Not even national timing laboratories, with a pile of cesium and H-maser references, can get their UTC(k) within 1 ns of UTC. Perhaps you can explain a bit more what you are actually doing. It sounds like an interesting application. Relative timing at the 1 ns level is easy. Absolute UTC timing at the ns level is much, much harder.

/tvb

----- Original Message ----- 
From: "Martyn Smith" <expertengineer at live.co.uk>
To: <time-nuts at lists.febo.com>
Sent: Sunday, June 24, 2018 3:37 AM
Subject: [time-nuts] 1 pps Sync'ing


> Hello,
> 
> I am a newbie question.
> 
> I have an application where I have a 10 MHz and 100 MHz squarewave output from my GPS frequency standard.
> 
> The frequency standard uses the PRS10 rubidium.  The 100 MHz output is just a 100 MHz VCO locked to the 10 MHz.
> 
> These outputs are disciplined by the GPS's 1 pps (as far as frequency).  But they are not in phase with it.
> 
> I need the rising edges of both the 10 MHz and 100 MHz squarewave outputs to be aligned with the GPS 1 pps (UTC) to within 1 ns.
> 
> Anyone already done this?  I'm sure I've seen a distribution amplifier that does this at 10 MHz.
> 
> But the 100 MHz is actually the more important one that I need to align.
> 
> Regards
> 
> Steve
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