Where can I learn more about which 10 MHz OXCO to pick for a GPSDO and why? - Page 1
Forum section: electronics / general

author: cdev
author_rank: Super Contributor
timestamp: November 25, 2018, 02:25:46 pm
content: Hello!I hope you folks don't mind my asking what is probably a sort of long question.How do I put this?I want to learn about how a GPSDO works. The best way I see to do that is to build one.I already have a GPSDO to compare it against, and a number of GPSs which are likely suitable so I need to get a 10 MHz OCXO. What should I look for in one, and why?I think I would like to build Lars's GPSDO because of its 1ns TIC feature, seems like a good choice because of both the TIC and suitability to the learning task, i.e. simplicity.It wants to use a voltage controlled oscillator and it prefers one where higher voltage increases its frequency, not decreases it.QuoteThere are a lot of OCXOs available on ebay.What are the best inexpensive OCXOs for GPSDO use? That probably depends on how much one is willing to spend. I would like to spend as little as possible but I think a good target amount if I am to keep it inexpensive is under $20 with $30 being the most I should spend and that only for an unusual exceptional value.There are ovened 10 MHz oscillators there for around $10 that I've seen used before that would likely be good choices.Are there any web pages that discuss the various issues (such as aging of the crystals, and how to recognize one thats likely to have lots of years of life left in it, and not)Bringing together lore on lots of different OCXOs all in one place?Well, I've sort of answered my own question. I'm going to post what I have found here.Lars has - as part ofhis GPSDO project, brought together a lot of links in the third of the PDFs which he was able to upload here, (it had to be split up)The links are at the beginning of the thread above in the file "What is Lars Arduino based GPSDO Controller page 15-18.pdf" (which contain his own GPSDO+TIC design)A lot of the people here have done a lot of work and contributed huge amounts of information on the design and use of time and frequency standards and measurement equipment, including GPSDO and TIC designs.Many of them also hang out on the time-nuts mailing list athttps://lists.febo.comTime-nuts is an extremely useful resource on everything time and frequency related.The US NIST also has a wealth of useful information on measurement of all kinds.An good example document is "Selecting a Primary Frequency Standard for a Calibration Laboratory" (There are hundreds of others):https://tf.nist.gov/general/pdf/2289.pdfOne good example I had seen before but not in its home page context, is in the web pages of the late Brooks Shera, W5OJM, who is now a silent key.He seems to have collected a great deal of useful GPSDO information, includinghis own designas well as links to a great many other projects.Now theycan be found via archive.org.TheWikipedia page on GPSDOalso has a great many good links.TVB at leapsecond.com has a web page offering a GPSDO simulationhttp://www.leapsecond.com/pages/gpsdo-sim/Also, there are agreat manyexcellent threads here on other user-designed and commercial GPSDO offerings, including some very affordable ones.