A Holdover Clock Achieving +/-1.5us Over 3 Days

Low cost and high holdover ability have been critical requirements for many instruments employed in IoT and smart power grid infrastructure networks. The significance on holdover performance is more and more obvious particularly in GPS denied, or GPS spoofing conditions concerning network security. In this paper, we report on a commercially available quartz-based holdover clock (GT-Q200) achieving <+/- 1.5us over 3 days.