Commercial Developments in Airborne VLF Navigation

Spurred by a rapidly growing need for long-range and remote area navigation, airborne navigation systems based on continuous wave very low frequency (VLF) transmissions have in a matter of a few years progressed from laboratory curiosity, past simple embodiment of the principle, to the stage of highly sophisticated and very complete navigation equipment. The systems to be discussed utilize the phase-stable transmissions of VLF communications stations and unique frequency transmissions available from some of the Omega network stations. Various phase comparison techniques are utilized to derive the navigational information.