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The data sheet of the AD8307 gives a supply filter circuit that is good enough to be used with the output of the arduino Keep in mind the AD8307 goes to 500MHz, good shielding is important for the low

Hi, I am starting to build a 'specan' ( https://hfsignals.blogspot.com/p/specan-reboot-of-w7zoi.html ) Mainly because I have a prototyping shield spare I will be using one.? It also has an SOIC 14

Sweet! You are the man! (Or whatever pronoun you're down with...) I've got a couple of these component testers from a couple years back that I got off of eBay. They could probably use a fresh remake.

Here is a direct comparison between running the SI5351 with a XTal or a TCXO TCXO frequency at 100th overtone (1GHz). Total width of the scan (100Hz) is 10e-7 of 10MHz XTal frequency at 100th overtone

Hope this topic does not overload your inbox..... The SW on github: https://github.com/erikkaashoek/Arduino_SI5351_GPSDO has been updated to automatically adjust for variations in the SI5351 XTal or

And this is a short video of the phase detector in action using a TCXO and 10 seconds phase averaging. http://athome.kaashoek.com/gpsdo/phase_detector.mp4 Yellow line goes high after PPS up edge and

A photo of the setup The white module at the left top is the thermally insulated SI5351 (just some foam tape wound around the module) The black thing at the right top is the phase detector with the

Not sure if I have 360 degrees view. I'm using an active antenna and a 2m antenna wire between GPS antenna and GPS module to keep the noise from the SI5351 (which is considerable) away from the GPS

Well that looks really good ! I'd connect the modules we have here and have a play with you (found them in various boxes). Only trouble is I've read that a clear 360 deg sky is needed for the GPS

The ultimate goal is not to use a TCXO but a stock SI5351 module with standard Xtal so I did some more tests using a standard SI5351 module with XTal and some thermal isolation. Soon it became clear

The STM8S103 has at least a couple of 16-bit timers (one is an 'advanced' timer), so I think it might well be a little better than the ATMEL's. Plus they boot up using their won internal RC CPU clock,

Thanks for the suggestion OneofEleven! The STM chip probably also has a better counter without the resampling to the CPU clock done in the ATMEL. To understand the source of the noise I measured the

All very good, well done ! To improve the resolution/stability you could clock the CPU directly from the Si5351, that way the CPU is phase locked to the clock of interest rather than using it's own

Using the phase measurement to measure every 10 seconds the averaged PPS error in nanoseconds (ignore the graph title) gave this result It seems there is still some noise on the phase measurement but

This project has really moved far from its roots now, and I mean it in a positive way. It’s hardly a version of the F2DC Gpsdo any longer with its variable measurement gate for faster convergence,

The Vphase can be input into the Arduino using analogRead(A0) With the integration time reaching 128 seconds the frequency error is below 1e-8 when the count error is 2 or less. Using the Vphase

The phase comparator can? actually be build from a single 7474. The 7474 has inverted Set/Reset but in?below spice mode the Set/Reset are not inverted so an inverter was added for the simulation

After building a phase comparator using a 7474 and a 7400 it became possible to observe every second the phase delta between the PPS and the 2.5MHz clock on a DSO The maximum phase comparator pulse

After updating the SW to allow setting the 10MHz from the SI5351 with a true accuracy of? 1/1000 Hz versus the TCXO the 3 hour trace looked like Measurement time fluctuated between 512 and 2048

An updated SW has reduced fractional spurs to an acceptable level (see github https://github.com/erikkaashoek/Arduino_SI5351_GPSDO ) Stability is great: Will test if further increasing the measurement