[time-nuts] Correcting jitter on the 1 PPSsignalfromaGPSreceiver.

Mike S mikes at flatsurface.com
Mon Sep 15 10:29:00 EDT 2014

On 9/15/2014 10:01 AM, Tom Miller wrote:
> Fast risetime pulses _are_ RF and need to be treated as such.

You say that as if simply saying it provides an explanation, or even a 
reason. Exactly what ill effect on a triggered measurement is there if 
one does not terminate a PPS signal properly? Does/can termination 
increase the slew rate or make the speed of propagation more consistent, 
which might make the measurement more accurate?

Like Tom said, what comes after the leading edge of a PPS signal (which 
is the measurement trigger) seems irrelevant.

A simple though experiment. If I take a high impedance measurement at a 
tap 1M from the source, and the cable ends another 100M away, how can 
the termination or lack thereof at that end effect my measurement of a 
single event? It's over 700 ns round trip away? If I repeat that event 
1/sec, is it any different? I can see where there would be a difference 
when I get close to a 700 ns cycle time, and likely before because of 
"ringing." But for a 1 second cycle? Someone will have to provide more 
than a dismissive "just because" to convince me.

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