HP HP-Bench-Briefs-1997-01-03 free download

File name HP-Bench-Briefs-1997-01-03.pdf

HEWLETT PACKARD SERVICE INFORMATION FROM HEWLETT-PACKARD 1st Quarter 1997 istory of Frequency Traceability at HP-Sanaa Clara Bob PifcocklHewIett-Packard year. The "flying clock's'' time would the flying clock trips. They would co- be checked at USNO in Washington DC ordinate the timing of DoD installa- prior to, and after, the trip to obtain clo- tions using GPS time as a reference. A Introduction sure for all the measurements taken single channel GPS receiver was ac- during the trip. Areport would be sent quired by SCD to use as a timing refer- Traceability to the National Institute of out, approximately one month after the ence. Since the original block of GPS Standards and Technology (NET) or trip, indicating time errors. That report satellites did not have SA (selective the United States Naval Observatory would be used with previous reports availability) installed, it was quite easy (USNO) for time and frequency mea- to estimate the long term frequency to achieve very good results. SA is the surements has been a concern for some error of the Santa Clara Division Time process of dithering the signals of com- customers of Hewlett-Packard for and Frequency Standard. mercial applications for security pur- many years. Even though our cesium poses. With SA, positioning can only (c beam frequency standards are recog- nized as primary frequency standards, DAS After the development and widespread be guaranteed to 100 meters or so. A USNO Data Acquisition System (DAS) some customers still request traceabil- usage of Global Positioning Satellite was then installed at SCD and used as ity. Without physically traveling with System (GPS) timing receivers, it be- the primary reference for time and fre- an operating frequency standard, the came unnecessary for USNO to make quency until recently. The DAS con- only way to achieve traceability is through some type of satellite transfer. This is fine, and is accepted by most customers, but there were still a few