In the mid 1990s I had to figure out how to set up a radio-based[0] NTP server. There is a radio broadcast from Ft. Collins Colorado (NIST) that is highly accurate. Someone else at the large company I worked for had purchased an antenna (as described in the article, it was "a ferrite bar inside a plastic enclosure" but no one so far had figured out how to use it. I got a telecom tech to temporarily install the antenna on a post in a small outdoor atrium at our computer center, then I put a Sparc station on a cart so I could wheel it out there to connect the antenna to the serial port. (Got some strange looks from co-workers on their coffee breaks). I did a lot of reading, spent some time getting the source code to compile correctly, and finally got it all working, so that a more permanent installation could be made and we would now have another low-stratum NTP server for our internal network spread across the state.

[0]http://www.articlesfactory.com/articles/computers/using-wwvb...

I live in an area without decent WWVB reception. So one of these days, my plan is to build a house range WWVB antenna so that I can get all the radio clocks in my house working consistently.