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LORAN-C Frequency Standard
FS700 — 10 MHz LORAN-C frequency standard
  • 10-12 long-term stability
  • 10-10 short-term stability (10-11 opt. )
  • NIST traceable
  • Reception throughout most of the northern hemisphere
  • Four 10 MHz outputs
  • Phase detector with analog output
  • 0.01 Hz to 10 MHz TTL output


Many complex electronic systems require a stable, highly accurate timebase. Communication, automatic test and measurement, and precision time-measurement systems all require accurate frequency standards. Traditionally, users have looked to atomic clocks (cesium) for high stability and accuracy. With the FS700 LORAN-C Frequency Standard, cesium-clock stability is now available at a fraction of the cost of atomic standards. The FS700 serves as a NIST traceable frequency reference in the US, Europe and Asia.

Cesium Stability

More than 50 LORAN-C transmitters are maintained throughout the Northern Hemisphere by the US Coast Guard. The timing of their transmissions is controlled by cesium clocks located at each transmitter site. The FS700 extracts the timing information from the transmitted signal and uses it to frequency-lock its own highly stable oscillator. The result is a 10 MHz output signal with the same stability as the cesium clock used to generate the LORAN-C transmissions.

Frequency Outputs and Phase Detector

Four 10 MHz sine wave outputs are available at the rear panel of the instrument, and an additional front-panel, adjustable frequency TTL source is also provided. A built-in phase detector measures the phase shift between an external timebase and the internal frequency source allowing you to easily calibrate precision oscillators between 100 kHz and 10 MHz. The FS710 distribution amplifier can help you distribute the 10 MHz reference signal throughout your facility.

Specifications
Receiver
Sensitivity Will lock with signal-to-atmospheric noise ratio of -10 dB or better
LORAN output Filtered and gain-controlled antenna signal, typically 6 Vpp
Station search All available stations programmed, Auto-Seek finds and tracks strongest station
Notch filters Six adjustable -30 dB notch filters, three at 40 to 90 kHz, three at 110 to 220 kHz
Frequency
Frequency stability  
     Long-term 10-12 (same as LORAN-C transmitter cesium clock)
     Short-term 10-10 (standard oscillator), 10-11 (low phase noise option)
Outputs Four 10 MHz outputs, 1 Vpp sine into 50 Ω
LOCK output Rear-panel TTL indicates receiver lock
Front-panel output TTL level output from 0.01 Hz to 10 MHz in a 1-2.5-5 sequence
Internal Oscillator
  Standard Option 01
Frequency 10.000 MHz 10.000 MHz
Type (ovenized) AT-Cut SC-Cut
Aging 5 x 10-10/day 5 x 10-10/day
Allan variance (1s) 5 x 10-11 5 x 10-12
Stability (0 to 50 °C) 5 x 10-9 <2 x 10-9
Phase noise    
     10 Hz   -125 dBc/Hz
     100 Hz -130 dBc/Hz -155 dBc/Hz
     1 kHz   -165 dBc/Hz
Phase Meter
Frequency output 0.01 Hz to 10 MHz in 1-2.5-5 sequence, TTL level. Can be 50 Ω terminated.
Oscillator input 1 kΩ, 0.5 V min., 5.0 V max.
Phase output 0.01 V/degree, 0 to ±360°. Output proportional to phase difference between OSC IN and FREQUENCY OUTPUT for frequencies between 100 kHz and 10 MHz.
Computer Interface
GPIB (standard) IEEE-488 compatible interface. All instrument functions may be controlled.
RS-232 (optional) 300 baud to 19,200 baud DCE serial interface. All instrument functions may be controlled.
Antenna
Type 100 kHz active antenna, w/ 40 kHz bandwidth band pass filter in base
Height 102"
Material Fiberglass whip
Base 2" dia. × 7.5", PVC
Mounting 3/4" FIPT
Output 50 Ω nominal, female BNC
Environmental -40 °C to 60 °C, 0 to 100 % RH
Lightning protection module (opt.)  
     Surge 18,000 A IEEE 8/20 waveform (based on ANSI C62.1)
     Frequency range DC to 30 MHz
     Throughput energy <16 µJ (based on 1 KV/nS waveform)
     Insertion loss <0.25 dB
General
Operating 0 °C to 50 °C
Power 100/120/220/240 VAC (+5 %, -10 %), 50/60 Hz, 50 W
Dimensions 17" × 3.5" × 17" (WHL)
Weight 14 lbs.
Warranty One year parts and labor on defects in materials and workmanship



Stanford Research Systems, Inc. • 1290-D Reamwood Ave., Sunnyvale, CA 94089
Phone: (408) 744-9040 • Fax: (408) 744-9049 • email: info@thinkSRS.com • www.thinkSRS.com
© Stanford Research Systems, Inc. 2003