Your research provided more justification why I run a GPSDO for my shack. The GPDSO provides a reference 10 MHz signal and 1 PPS that I use to drive a Raspberry PI NTP. I followed the instructions here: http://www.unixwiz.net/techtips/raspberry-pi3-gps-time.html

I used a GPSDO that I purchased on Ebay from BG7TBL like this: https://www.ebay.ca/itm/112700839490?hash=item1a3d7e5642:g:TqQAAOSwPPpaOhYT

Another choice is to use a GPS USB dongle and BktTimeSync: https://maniaradio.it/en/bkttimesync.html

Another advantage there are ways to grab the lat and long from the GPS USB dongle and use WSJT-X autogride feature to load your grid square.

Hope this helps!

73 de VA3IQ

Lawrence