The Austin EMC frequency standard is a battery backed-up,
disciplined quartz oscillator that is phase locked to the Raymondville,
Texas slave station of the South Central U.S. Loran-C navigation chain.
Loran-C transmitters are controlled by redundant cesium primary
frequency standards.
They are traceable to the U.S.Naval Observatory.
The published frequency accuracy of Loran-C is 1X10-12 , which is 20 to
100 times better than WWVB. By utilizing a ground wave signal
error introduced by diurnal and other propagation phase
shift anomalies such as solar flares and meteor showers as is common with
WWVB is reduced. This means that accurate calibrations can be made at any time of day
and in less time which converts to a cost savings to the customer.
The above system has been augmented by a GPS frequency and time receiver which is even more accurate.
A typical calibration includes the following steps:
1. Equipment is temperature stabilized.
2. High accuracy equipment is allowed additional time to reach
stabilization.
3. Initial frequency is measured and recorded. This is optionally
reported on certificate.
4. An adjustment is made to remove the frequency error.
5. A calibration label is affixed and a calibration certificate is issued.
Capability
Direct measurement uses a phase locked HP5345 frequency counter which utilizes a reciprocal technique with a 500 MHz. gate that provides a constant resolution regardless of frequency.
| 1 Second | +-4.6X10-9 | 9 Digits |
| 10 Seconds | +-4.6X10-10 | 10 Digits |
| 100 Seconds | +-4.8X10-11 | 11 Digits |
| 1000 Seconds | +-6.6X10-12 | 12 Digits |
Fractional frequency offset uses the HP5345 to measure the time difference accumulated between two phase locked Frequency Synthesizers set to 100 Mhz. and 100 Mhz plus 1 Hz.with one locked to the house standard, and the other locked to the standard being measured. When both frequencies are equal the time difference will be a constant 10 Nanoseconds which can be measured with a resolution of 2.02 picoseconds in 100 seconds. For signals of 10, 5, and 1 Mhz any offset will be multiplied by a factor of 10, 20, and 100.
Fractional offset time averaged accuracy
| 1 Megahertz | 5 Megahertz | 10 Megahertz | |
| 1 Second | +-4X10-12 | +-2.9X10-12 | +-2.6X10-12 |
| 10 Seconds | +-2.6X10-12 | +-2.3X10-12 | +-2.2X10-12 |
| 100 Seconds | +-2.2X10-12 | +-2.1X10-12 | +-2.06X10-12 |
This service is being offered for a limited time at an introductory price of $195 per device.