PURPOSE: To eliminate the influence of a space wave on a synchronous path through a simple system and to improve position measurement precision, by allowing a slave station to transmit a radio wave phase-locked to a radio wave from a master station in the daytime in which the radio wave is stable in state, and allowing the main and slave stations to perform transmission independently of each other when the influence of space wave is large, in the nighttime, etc.
CONSTITUTION: A switch 33 is closed when space waves are less and the radio wave is stable in state in the daytime, etc. and opened in the nighttime when space waves become intense. Therefore, when the switch 33 is closed, an error voltage ER from a phase different discriminator 31 is stored in a phase different information memory 32 through the switch 33 and also applied to a variable phase shifter 30. Then, the phase shift extent of the variable phase shifter 30 is adjusted to that the phase difference between signals to two input terminals of the phase difference discriminator 31 is 0 or constant, and a signal of 0.2f generated on the basis of the received radio wave from the master station and a signal of 0.2f generated in the slave station are phase-locked. Then, the slave station 21 transmits the signal phase-locked to the radio wave from the master station in the daytime, and a signal subjected to phase shift determined on the basis of the information stored in the phase information memory 32 in the nighttime.
OOHASHI WATARU
NAGAO KATSUYUKI
