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Effects of the Rooftop Environment on GPS Time Transfer



Michael A. Lombardi, Andrew N. Novick


We examine the effects of the rooftop environment on GPS time transfer, in particular the effects of multipath reflections from nearby metallic objects. Three different antennas sites were selected on the roof of the NIST laboratories at Boulder, Colorado, each with different multipath characteristics that we discuss in detail. Simultaneous tests were conducted at each site using the same model of L1 band GPS receiver, but varying the antenna type. Four different types of active antennas with low noise amplifiers were used at each site: a patch antenna, a patch antenna with a simple choke ring attached, a quadrifilar helix, and a ¿pinwheel¿ antenna with an aperture coupled slot array design. Results are presented that demonstrate how each antenna performs in each multipath environment, using the time deviation as a metric. We also discuss the potentially harmful effects to time transfer caused by RF interference from other active GPS antennas located on the same roof.
Proceedings Title
Proc. 2006 Precise Time and Time Interval Meeting
Conference Dates
December 5-7, 2006
Conference Location
Reston, VA


antennas, GPS, multipath, time transfer


Lombardi, M. and Novick, A. (2006), Effects of the Rooftop Environment on GPS Time Transfer, Proc. 2006 Precise Time and Time Interval Meeting, Reston, VA, [online], (Accessed June 23, 2024)


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Created December 5, 2006, Updated January 27, 2020