Next, I note a couple of problems I had with the first GPS receiver I tried, and how I cured those with a different GPS receiver to produce a stratum-1 NTP server consuming about 4 watts.
As an experiment, I purchased one of the low-cost credit-card-size Raspberry Pi computers, and have configured it to run NTP (Network Time Protocol).
I have also used this board with a GPS receiver with pulse per second (PPS) output to make a stratum-1 NTP server, but as I know little of Linux, it has taken some time to achieve this aim!
) or certain windows with a lining to stop incoming heat, or wall construction including metal, you may still need an outdoor antenna, and almost certainly if you live in a basement!
Whilst weather will normally have only a small effect in the signal - e.g.
There are some helpful Linux commands scattered throughout this page.
These notes are almost as much for my own records for the next time I need to visit this project, but I hope they may be helpful to others.
Note that the Adafruit GPS Hat uses GPIO 4, physical pin 7, so you would need to change the commands given in this document.
Later additions have included remote monitoring of the NTP server performance, and more general monitoring of the Raspberry Pi using the standard SNMP functions, with an additional CPU temperature monitoring add-on. Note that good performance is dependant on the GPS unit having a clear view of the sky, particularly the southern part of the sky if you are in the northern hemisphere.
With older GPS receivers this required an outdoor antenna, but more modern units such as those mentioned here may well work indoors providing that some sky is visible, perhaps on the top floor of the building (as I am).