ms calculation & precision improvements using continuous fractions about si5351 HOT 3 OPEN

A good place to find the CF code to play with it is the 'si5351-experiments' repository (https://github.com/fventuri/si5351-experiments). If you look at the examples in the README (https://github.com/fventuri/si5351-experiments?tab=readme-ov-file#si5351-experiments) it should be easy to see how you can run it.

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Thanks for the really detailed feedback!

I definitely became aware of the weakness in the library of calculating fractional Hz parameters when I tried using it to generate WSPR and FT8 for higher HF bands and VHF. I'm definitely interested in pursuing this, and follow up on a bunch of the other issues and PRs that have accumulated. I was without a workbench for a few years and have only recently been able to set up a modest new bench, which has stopped me from doing any real work on this library.

I do have a GPSDO, and I'm going to be using the Si5351C in my new "Project Yamhill" board so I should be able to do this if I can get that GPSDO set up again. Give me a few weeks or so to finish up some other things and I'll take a look to see if I can accomplish this. I think it would make me and a lot of people happy.

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Since writing here earlier this year, using Franco's code I've made useful progress in applying continuous fractions (CF) to the NT7S Si5351 library in the context of an Arduino IoT33 rather than simply the Uno.

Not only do CF work very well in greatly improving the frequency precision but the use of the CLKIN pin has allowed better phase noise performance. Precision can now be so good that some of the special effort previously needed can be avoided if they are used with a truly double precision float environment. All this has ended up unearthing several issues in the library and with the application of the si5351 20-QFN C version part.

Though I'm not finished with these efforts, because they may be useful to others here, I'm attaching a first draft describing some of what I've found useful in case it may save others time and effort.

Glenn n6gn

Si5351 NT7S notes.pdf

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