[time-nuts] A bit more on what going on with the Loran sites

Pete Lancashire pete at petelancashire.com
Tue Mar 27 17:49:56 UTC 2012


>From GPS World

This week, UrsaNav once again transmitted from the former USCG Loran
Support Unit (LSU) facility in Wildwood, New Jersey. To ensure that
those interested understand that the USCG has no intent to acquire,
operate, or provide a wireless time technology or services, UrsaNav
has renamed the LSU — it's new facility name is the Diamond Beach
Facility, or “dBF.”

In a statement released today, UrsaNav said:

"Our main purpose for on-air testing at this time is to demonstrate
wide-area precise time distribution using terrestrial, ground-wave RF
solutions. However, a robust timing solution uses on-signal data
channel(s) for nanosecond-level corrections, so we are also testing a
variety of modulation techniques that provide significant throughput
gains over the current 100-180 BPS methods.

"Our current equipment suites consist of the Nautel NL Series
prototype transmitters, Symmetricom Timing and Frequency Equipment
(TFE), and UrsaNav UN-150 eLoran Timing Receivers.

"We are not simply transmitting eLoran. We are also evaluating some
improvements to eLoran that do not change the underlying signal
structure. Finally, we are testing various alternative LF solutions
that include new waveforms and modulation techniques.

"We have established preliminary monitor sites at five locations:
Boston, Massachusetts; Chambersburg, Pennsylvania; Leesburg and
Chesapeake, Virginia; and Charleston, South Carolina. We are scouting
for additional monitor sites at distances of up to 1,500 miles from
our current transmitting location.

"During this week’s testing, we tightened the synchronization of our
transmissions to within 10 ns of UTC. We tested continuously for
periods in excess of 24 hours. Without the use of any propagation
corrections or differential monitoring, we successfully demonstrated
UTC traceability to within +/- 30 ns at 160 miles and to within +/- 70
ns at 500 miles. Several acquisition trials showed that our receivers
can very quickly acquire the LF signal and steer to within 50 ns of
UTC. At all distances, our receivers met the ITU and ETSI Maximum Time
Interval Error (MTIE) masks for Primary Reference Clocks.

"Additional on-air tests are planned for next week, so stay tuned for
the third part of our continuing series on wide-area timing."



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