TIME OF DAY FROM OMEGA VLF SIGNALS

Omega VLF transmissions are synchronized to UTC and can thus be used not only for navigation but also for determining time. An inexpensive DSP-based 'clock' card is described which plugs into a personal computer and by means of suitable software phase locks on to Omega signals from a simple broadband VLF preamplifier. Within a few minutes from daytime system power-up, the clock card is able to supply time of day (UTC) to an absolute accuracy of a few microseconds. Because of the Omega repetition period this time has an ambiguity of module 10 s, but this can normally be readily resolved by the user entering approximate wristwatch time at the keyboard. The clock output is available both in machine readable form to the host computer and as a one second pulse direct from the Dsp clock card.