[time-nuts] NTP/1-PPS/RS232 question

Bob Stewart bob at evoria.net
Sun Sep 8 15:53:47 UTC 2013


Hi Mark,

Have you done any measurements on the 1PPS to see of their 10ns jitter figure is correct?  I was doing some comparisons here against my UT+, but I don't have GPIB hooked up yet, so I can't get anything more than a general feel.  If you do any accurate measurements, could you please post them?  Eventually I hope to set things up so I can compare the jitter between the two with the sawtooth figure the UT+ outputs.

Bob





>________________________________
> From: Mark Sims <holrum at hotmail.com>
>To: "time-nuts at febo.com" <time-nuts at febo.com> 
>Sent: Saturday, September 7, 2013 9:15 PM
>Subject: [time-nuts] NTP/1-PPS/RS232 question
> 
>
>I got in those Adafruit GPS boards.  They are a very nice little GPS.   VERY sensitive.  I could get good lock indoors on my (windowless) kitchen floor.  The house is 2 story,  stucco with wire mesh in the stucco.   I could also get lock in a restaurant that had a tin roof.  We were far from any windows.
>The 1PPS signal is normally low and pulses high for 100 milliseconds.  The RS-232 adapter board that I built feeds this into an RS-232 transmitter chip (MAX3232),  so on the interface connector CD will be at +V and pulse down to -V.  Is this what stock NTP likes?
>Also,  I laid out the adapter board so it an accommodate a Trimble Resolution T or a Crius CN06 receiver.  The Crius receiver uses a U-Blox NEO-6M receiver.  They can be had for around $22 at HobbyKing.   They seem to perform even better than the AdaFruit module.  It looks like you will need to bodge a wire onto the TIMEPULSE pin to use it for 1PPS.                           
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