TIME OF DAY FROM OMEGA VLF SIGNALS

Omega VLF transmissions are synchronized to UTC and can thus be used n ot only for navigation but also for determining time. An inexpensive D SP-based 'clock' card is described which plugs into a personal compute r and by means of suitable software phase locks on to Omega signals fr om a simple broadband VLF preamplifier. Within a few minutes from dayt ime 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 wris twatch time at the keyboard. The clock output is available both in mac hine readable form to the host computer and as a one second pulse dire ct from the Dsp clock card.