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Erik, This looks very impressive. I’ll order the qrplabs 25 MHz Tcxo and try your software when I’m back from holiday!

Using the 10MHz output as external reference to a Siglent spectrum analyzer made it clear the frequency is stable enough to measure a 1GHz signal with 10Hz or better accuracy but the fractional spurs

A graph showing how the set frequency is corrected over time to keep the output at 10MHz The measurement was started 30 seconds after power on. After roughly 30 minutes the TCXO seems to become stable

Test seems to be OK. afreq is the frequency times 100 that is set to create the 10MHz GPS locked output. Stable enough to go to a 400 seconds period using a 1e+9 pulse count Delta's for the last 5 400

Github https://github.com/erikkaashoek/Arduino_SI5351_GPSDO -- HBTE Files section: /g/HBTE/files Erik, PD0EK

Where in the files section? dave k2lyv

Sverre, thanks for the reference. After a lot of testing the culprit was indeed the Etherkit library. Using the very small routines from Marcus W3PM I made a version where the actual frequency after

One of the inspirations for the F2DC Gpsdo does not use the Etherkit library, as far as I recall. Maybe some ideas may be had from there? That is: G. Marcus W3PM,"An Arduino Controlled GPS Corrected

While doing tests at 1GHz using the 5th harmonic of a 200MHz output of the Si5351 the used Etherkit SI5351 library appears to have a bug/limitation that limits the resolution of the frequency

Did some more experiments and decided the X-tal in the SI5351 is the limiting factor in stability so replaced it with a cheap 26MHz TCXO

Hello Dennis, not sure, if you are aware, that there is a very refined component tester using minimal hardware based also on the ATMEGA328. It is a design by Markus Frejek further developed by

Dennis Zabawa <kg4rul@...> added folder */Honey I Shrunk The Component Tester - Build Description* --- The following files have been uploaded to the Files area of the [email protected] group. *

To understand the impact of temperature fluctuations the simulation is extended to have? a perioding temperature change causing a 2 Hz temperature fluctuation over a 1.6 hour period. The feedback

To better understand I did some simulations. Once the measurement time is above 10 seconds the 100ns PPS jitter is no longer relevant given the measurement time and measurement frequency. Drift is a

Very interesting discussion. The Lars Gpsdo is documented here: https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/ It is a phase-locked loop rather than a

My SI5351 never became stable enough to go beyond 400s (but I now understand this may be the PPS jitter) Yes. Minimum frequency compensation of the SI5351 is 0.01Hz -- HBTE Files section:

Alan, So once the 400S measurement period is reached and the variations are sufficiently low (say below 20) the control loop should change from jumping to a low pass filtered compensation in the hope

The jitter in the 1PPS signal depends on the GPS receiver, an older unit from 10 years back may have around 100nS jitter, a recent unit around 20-30nS. Receivers are of two kinds position finding –

SPARKFUN? ARDUINO COMPONENT TESTER RE-PACKAGED I recently came across an Arduino based, Component Tester project by SPARKFUN?. Arduino Component Tester ( https://www.sparkfun.com/news/3909 )

Hi Erik A couple of questions: Is there a particular reason why you stopped at 400 s as the maximum measurement time? And second, is this how you compute the frequency error corresponding to a single