[ntp:questions] Very large jitter and offsets on GPS ref clock after upgrade to "p5"

Chris Albertson albertson.chris at gmail.com
Mon Jan 9 20:00:18 UTC 2012


>
>
> With +/- 12VDC RS232 drivers, I've done 800' and 1000' runs
>  of Cat5e @ 19.2Kbps without issues.
>
>  {On the other hand, on cables designed for RS232 decades before Cat5e,
>   I've had issues at one tenth that far, (~100pf to 200pf / meter)
>   at 19.2Kbps.
>
>
What I may have is "self interference" of some kind.  Most of the pluses
get through just fine.  A few don't.   Perhaps the Tx wire is close to the
PPS wire.   I wonder if sending data at 9600b could effect the signal on a
parallel conductor?    When I look at the logs, I see the error is almost
periodic.   I've noot looked really close but the errors do seem to be
equally spaced.   I saw this kind of thing once at work and it turned out
to be an air traffic control radar a couple miles away.   I doubt this is
the case now but I do have ASCII in the same cable

Your test that you can send data over cat-5 is not the same as sending two
streams of data over cat-5.

I'm sure I could fix this be using diferenctial drivers on a twisted pair
but I think moving the computer is the best plan.  Then the PPS will be
sent over RG58 coax and level converted just inches from the computer.


Chris Albertson
Redondo Beach, California


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