Time and Frequency Measurement
I've always been interested in the technology used to measure things very accurately, and as a ham radio operator, my focus rapidly became measuring frequency, and its inverse, time (or is it the other way around?) to the Nth degree. In particular, I'm interested in how radio can be used to make precise time and frequency information available to end users. This page has some details of my current experiments.
Below are links to some general areas in which I've experimented. Most of my data and results are at www.febo.com/pages. This includes not only purely time and frequency related materials, but also stuff from my more general Geekworks pages as well; there's a lot of overlap between the two topics.
Going to www.febo.com/pages will show you a list of directories; clicking on one will take you to its contents. Some of the directories will be full-blown web pages, others may contain just some pictures or plots, or further subdirectories containing who knows what.
I have written a bunch of scripts to automagically generate and update charts from my data logging experiments. You can see the results:
- www.febo.com/time-freq/plots has phase plots of my frequency standards versus GPS and other experiments. It also has charts monitoring temperature in my lab, and the signal strength my GPS receivers are seeing.
- www.febo.com/time-freq/ntp/stats has charts showing the performance of my NTP time servers.
NOTE: I've recently relocated and had to pack up my lab. Until I get things going again, this is old data.
I've written some programs that do the work of generating these plots. You can learn about them, and grab them for yourself, at www.febo.com/time-freq/tools.
There are three principal methods used to disseminate time and frequency information from national standards institutes to end users. They are: (a) VLF radio stations like WWVB; (b) the LORAN-C navigation system; and (c) GPS satellites (there are numerous other systems that have been used, but they are either obsolete, very specialized, or of relatively low performance). I've been experimenting with all three, and there's a page here for each:
In addition I've create a bunch of other pages related to other aspects of precise time and frequency measurement:
- The ARRL Frequency Measuring Test (and measuring frequency off the air)
- Frequency Measurement Papers/References/Links
- Some Stuff on Network Time Protocol (NTP)
- Performance of the HP-5370B Counter
- 10GHz Oscillator Experiment
- Stability and Phase Noise Specs
- Leap Second 2005