Characterization of the clock in a new inexpensive GPS receiver: the Magnavox MX4200

Abstract

A new generation of inexpensive GPS receivers is emerging, which utilize temperature compensated crystal oscillators (TCXO) as clocks. The MX4200 has been chosen as a representative sample of this emerging technology receiver. A detailed discussion on the receiver architecture and its implications in the measurement process is given. Experiments on the sensitivity of its clock to environmental effects, as well as the duration of the transient regime are described. One limitation to the use of these receivers in geodetic applications is the stability of its clock. The noise in the receiver clock has been characterized by the Allan variance for sampling intervals up to 4000 seconds. The implication of the noise levels for short time intervals on the applicability of the receiver to high precision work is examined.