A Proposed Ranging System with Application to VLF Timing

In general, without a clock it is not possible to determine the range between a radio transmitting and receiving site by making only passive observations at the receiving site. However, if the medium is dispersive, signals transmitted simultaneously from the same site, at different carrier frequencies, will not arrive simultaneously at some distant point. Thus, the difference in arrival time is related to the observer's distance from the transmitter. This effect is considered in conjunction with the VLF two-frequency timing system.