1 Loran Timing ILA – 36 th Convention and Technical Symposium Orlando, Fl., Oct Arthur Helwig Gerard Offermans Christian Farrow

Outline Timing and Frequency use Developing High-end Loran-C timing equipment (recap) Developing Low-end Loran-C timing equipment –Low-cost oscillator characterizaton –Received signal –Combining the two Conclusions

Outline Timing Frequency Time and Frequency Receiver outputs: 10 MHz MHz MHz Necessary input: eLoran/Loran-C signal Receiver outputs: Frequency outputs, plus: 1 PPS (aligned to UTC) 10 PPS 100 PPS Serial output for Time of Day message Necessary inputs: eLoran signal Data channel for UTC information

MTIE / TDEV Relevant measurements: MTIE – Maximum Time Interval Error (MTIE): The maximum peak-to-peak delay variation of a given timing signal with respect to an ideal timing signal within an observation time  n    for all observation times of that length within the measurement period (  ). TDEV – Time Deviation (TDEV or σ x (  )): A measure of the expected time variation of a signal as a function of integration time. TDEV can also provide information about the spectral content of the phase (or time) noise of a signal. TDEV is in units of time.

ETSI – EN ETSI EN V1.1.1 ( ) Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 3-1: The control of jitter and wander within synchronization networks 864 ns / day ASF fluctuations not a problem

Loradd UTC series All functionalities of a normal LORADD receiver Ovenized crystal for improved stability and hold-over (SRS SC10) 10 MHz, MHz and MHz outputs 1 PPS (Loran-C derived) output 1 PPS (GPS derived) output Loran-C Timing Source Station selectable

Test results - MTIE ETSI PRC Mask Loradd UTC performance 10 ns

Test results - TDEV ETSI PRC Mask Loradd UTC performance

Low-cost Market demand for low-cost frequency-only receiver Frequency lock to a single Loran station No hold-over required Low-cost oscillator means shorter integration of received Loran signals

Loradd-F Low-cost VCO No GPS 10 MHz output via SMA Loradd-F

Low-cost oscillator characterization Crystal oscillator frequency varies Graph displays frequency vs time Receiver operating at room temperature After warming up for several days Most likely still due to temperature variations Free-running VCO Time (s) Frequency error (ns/s)

200 s 4e-10 Low-cost oscillator characterization Time interval: 200s Frequency error: 4e-10 Phase error (over 200 s): 40 ns MTIE mask: 25 ns When left uncorrected, MTIE mask is broken at this point. Free-running VCO Time (s) Frequency error (ns/s)

Received signal characterization Rugby (6731Y) 5-second independent measurements 6731Y std=10.44 ns TOA of Rugby Reeuwijk (408 km) Time (s) Measured TOA (ns)

Received signal characterization Rugby (6731Y) 5-second independent measurements with 3-point moving median filter 6731Y std=8.18 ns Transmitters are currently broadcasting in a 10ns “grid” 200 s TOA of Rugby Reeuwijk (408 km) Time (s) Measured TOA (ns)

Combining the two Low-quality VCOLoran TOA MTIE

Combining the two Low-quality VCOSimulated Loran TOA (σ=3.5 ns) No timing steps MTIE

Conclusions Loradd UTC with high quality VCO fully meets MTIE specification Loradd-F with low-quality VCO does not yet meet MTE spec at 25<τ<110 s –Temperature controlled VCO –Higher grade VCO Timing steps in transmitter need to be investigated. Elimination will result in reduced cost receivers.