Using a low cost Raspberry Pi for a Stratum 1 Time Server. The GPS module is connected through an isolated RS485 link. The link between the GPS and RPI can be over 100m.
The GPS module is designed to fit in a PVC tube of 50mm (2 inch) for a cheap and easy waterproof enclosure.
The power supply is provide through the 40 pins connector and an isolated step-up provide 24V to the GPS head.
Connectors and Accessories / Euro Connectors
The enclosure is a PVC pipe adapter I found at a local store for 1.2 Euros :
Once it's closed it looks good :
The top is screwed and it has an inside seal, I just needed to cut a piece of plastic to fill the void.
I'm running a test with a 100 meters (328 feet) ethernet cable between the RPI and the GPS head and it works without a hitch. It should work with longer length without problem, the limiting factor should be the voltage drop but at 24V the current is small, and one pair in the cable is used for GND and another for +24V.
Basically the project is finished and it's working great. I need to publish the schematics and the gerber for the boards and add a step by step howto to ease the replication process.
On problem though: It is my first project with a RPI4,and the board is running really hot. I'm still waiting for my enclosure but there is no way the processor will run full speed without throttling when the hat is on and without heat sink nor fan. So I will make a new HAT with a fan... In this version I have a RTC with a backup battery, it works great but I do not think it's really useful in real life. So in the next version I'll remove the RTC to make room for a fan and I'll add few LED to show the status of the NTP server.