Terry wrote:

> I have to sort out now is the timing pulse. it looks
> horrible on vtscope, a sort of double humped thing

I'd guess you have some high pass applied to the shaped
PPS, perhaps the input stage of the Octo?

Does it look anything like http://abelian.org/vlf/tmp/170617a.gif

Is it possible to reduce the PPS pulse width?  Say to
10mS or 5mS?

> Are you using a square pulse from the GPS to feed
> the RC conditioner?

Yes, it's a 2mS rectangular pulse from the GPS, through
a buffer (a hex inverter), then a simple RC low pass
filter to shape the pulse suitably for centroid measurement.

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Paul Nicholson
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