A synchronization system of very low-frequency interferometers

A solution to the problem of synchronization of spaced autonomous data-acquisition systems and obtaining stable reference-frequency signals for measuring phases of very low-frequency (VLF) radio signals is described. The expediency of using GPS receivers and tunable crystal oscillators in the synchronization system of VLF interferometers is grounded. Measurement results of the phase stability of the reference signal, received from the designed device, are presented. The short-term frequency stability of a 200-kHz pulse signal at the output of the designed unit is no more than 1.5 × 10 −7 , allowing one to measure the phase of VLF signals with an accuracy of no worse than ±0.81°.