check_ntp-simple Check NTP on multiple servers NTP-Setup-On-Solaris
https://www.elektormagazine.com/articles/raspberry-pi-pico-makes-an-msfsdr
https://forums.raspberrypi.com/viewtopic.php?t=20968
http://www.buzzard.me.uk/jonathan/radioclock.html
https://www.lemonfool.co.uk/viewtopic.php?t=15309
https://www.electronicsweekly.com/blogs/engineer-in-wonderland/nice-little-time-receiver-module-for-msf-or-wwvb-2024-05/
http://www.users.globalnet.co.uk/~arcus/avr-ntp/