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Home » PPS

Raspberry Pi Stratum-1 NTP Server Statistics

April 12, 2016 by Jack Zimmermann Leave a Comment

MRTG main screen for a NTP serverAfter becoming a full-fledged time-nut (I’m compiling a new Linux kernel on my second NTP server as we speak), I have started to use the statistics that I usually install on a server just to keep a check on it. Sure, when installing something like MRTG, it’s great to see if something is clogging the system, but mostly, it’s unused. But when working with an NTP server a lot of factors start to make a difference. The temperature of the processor (the whole computer actually, mostly due to crystal drift), the load of the CPU’s, etc.

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Filed Under: Raspberry Pi Tagged With: GPS, GPSDO, NTP, PPS, Server

DIY Reference 10 MHz Distribution Amplifier

March 21, 2016 by Jack Zimmermann 2 Comments

Extron Ada 4 300MX Video Distribution AmplifierI wanted to get a distribution amplifier for my 10 MHz lab reference signal from my GPSDO to feed my equipment, like my timer/frequency counter, signal generator, and other stuff. I also needed a way to distribute a 1 PPS signal from my Trimble GPSDO to my NTP servers and other clocks and monitoring systems. The Trimble only got two 10 MHz outputs and one 1 PPS signal output, so I needed to add more, especially for experimentation.

I saw this video by Gerry Sweeney where he modifies an Extron 300MX video distributions amplifier, adding a rubidium reference standard and was intrigued. But I changed the modifications to fit my needs and here is the result.

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Filed Under: Electronics Tagged With: Electronics, Lab, PPS

Increase Pulse Width 1 PPS signal from GPSDO

January 28, 2016 by Jack Zimmermann 3 Comments

Update: You can download the Eagle PCB files for the PPS Pulse Width Extender here.
The PCB is made to fit the Hammond 1455C802BK enclosure.

I have two Stratum-1 NTP servers using Raspberry Pi 2’s as servers. But the two setups are entirely different.
trimble-gpsdoMy primary NTP Stratum-1 server is available at ntp.jacken.se, but it is also in the .se pool of ntp.org. It’s a Raspberry Pi 2 I use a Raspberry Pi 3 that I have connected a U-Blox Neo-7 GPS receiver. But I’m not using the 1 PPS signal coming out of the U-Blox. I have a Trimble GPSDO that I bought from eBay. The unit has two 10 MHz lab reference outputs and one 1 PPS output. But after measuring the signal coming out from the GPSDO, I realized that the timing speed for the seconds “Tick” was only 10 µsec which is way to fast for the Raspberry Pi to pick up as an interrupt on one of the GPIO pins. pulse-increaserSo I built a pulse extender, making the pulse around 250 milliseconds instead. And now the Raspberry Pi picks up the pulse without problems. Some GPSDO units can set the pulse width by programming the unit via a serial port, but I can’t find that feature on this unit (which is poorly documented and was OEM made for some other manufacturer), so I had to do it with hardware. So how does it look when crunching the numbers on it?

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Filed Under: Linux, Raspberry Pi Tagged With: Linux, NTP, PPS, Raspberry Pi, Server

Portrait of Jack Zimmermann I'm a Swedish computer old timer hacking away on computers since 1979. I'm a total Apple and Linux gear head. Right now, I'm really into electronics. [Read More]

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