A New Frequency Calibration Service Offered by the National Bureau of Standards

Kamas, G.; Jespersen, John

doi:10.1109/freq.1983.200715

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“…During 1983, the NBS Frequency Measurement Service was announced at both the Frequency Control Symposium [4], and the Precise Time and Time Interval Meeting [5], two established meetings attended by the time and frequency community. A measurement system was shipped to the service's first customer (the Federal Aviation Administration) on January 19, 1984.…”

Section: Chaptermentioning

confidence: 99%

“…Throughout the 1980's, the attention of the time and frequency community had begun shifting away from LORAN-C and towards the Global Positioning System (GPS), an orbiting constellation of satellites that each carried atomic oscillators. The first experimental GPS satellite was successfully launched in 1978, GPS signals were routinely used by NBS for time and frequency comparisons by 1980 [11], and NBS had launched a GPS-based time service, called the Global Time Service, at about the same time the FMAS began in 1984 [4]. GPS performance was superior to that of LORAN-C, the signals were easy to receive, and the coverage area was essentially worldwide.…”

Section: Chapter 1 -History and Physical Descriptionmentioning

confidence: 99%

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Remote frequency calibrations :

Lombardi¹

2004

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The FMAS is a network of individual frequency measurement systems located at each of its customer's laboratories, and connected by telephone lines to the NIST laboratories in Boulder, Colorado. Each individual system includes a GPS satellite receiver and antenna, a time interval counter, and a computer that controls the measurements. The data collected from all customer sites are stored and archived at NIST, and calibration reports are sent each month to every customer. Several master units are also maintained by NIST. The master units, which comprise the same hardware and software as the customer's units, continuously compare the received GPS signals to the national frequency standard. In this way, NIST can continuously monitor the frequency uncertainty of each customer's unit, and the uncertainty of their primary frequency standard. This chapter begins by providing a history of the FMAS. It then provides a physical description of the FMAS components and facilities. Remote Frequency Calibrations: The NIST Frequency Measurement and Analysis Service Item Description Solid State Flash Memory Disk megabyte or higher capacity with embedded ROM-DOS operating system. Measurement software is preinstalled. Video Card Compatible with minimum requirements of VGA standard, 640 × 480 resolution, 16 colors. Modem 14.4 kilobit per second modem (V.32 standard), compatible with existing software. Time Interval Counter Custom designed counter with 8-channel multiplexer, 24-bit frequency dividers, 30 ps resolution. Accepts 1, 5, or 10 MHz external time base signal, provides RS-232 interface for GPS receiver [16]. GPS Receiver Motorola Oncore 8-channel parallel tracking GPS receiver (mounts on time interval counter card). GPS Antenna Active GPS antenna with > 30 dB gain, mounting hardware, and cable. The cable is made to customer's specification. Total signal loss on cable should not exceed 20 dB for the GPS L1 carrier frequency of 1575.42 MHz. Various types of coaxial cable are used to meet this requirement. Uninterruptible Power Supply (UPS) 500 VA supply with four AC outlets. BNC Cables BNC to BNC cables provided for all 5 measurement channels.

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Section: Chaptermentioning

confidence: 99%

Section: Chapter 1 -History and Physical Descriptionmentioning

confidence: 99%