[time-nuts] NTP/1-PPS/RS232 question
Bob Stewart
bob at evoria.net
Sun Sep 8 11:53:47 EDT 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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