LORAN-C Band Data Collection Efforts at Ohio University Presented by Curtis Cutright to the International LORAN Association 32 nd Annual Convention and Technical Symposium Boulder, CO November 6, 2003

Ohio University Avionics Engineering Center Outline Task overview Data collection system overview –Airborne data collection equipment –Lab data collection equipment –Initial data collection results Task progress

Ohio University Avionics Engineering Center Task Field a data collection system capable of digitizing storing atmospheric noise for subsequent analysis Integrate this system into an airborne flight platform Perform data collection under varying atmospheric conditions

Ohio University Avionics Engineering Center Purpose Develop threat models for aircraft in flight Precipitation static (p-static) Atmospheric noise Man-made noise(cross rate, CW) Lightning

Ohio University Avionics Engineering Center Purpose Identify all trade-off’s for E and H-field antennas, SNR, phase error, saturation, bandwidth

Ohio University Avionics Engineering Center To be determined Is ground-based noise the same as airborne noise(E-field and H-field) Aircraft man-made noise CW interference environment Determine actual P-static mechanism Phenomena under thunderstorms Antenna and pre-amp performance

Ohio University Avionics Engineering Center Data Collection Simultaneous ground and aircraft RF data collection (Using DataGrabber) 2 channels, 16-bits samples, 400 kSamples/s LORAN receivers for performance assessment GPS WAAS for position reference

Ohio University Avionics Engineering Center Data Processing P-Static Characterize E-field and H-field antenna performance Compare measured lightning noise with predicted noise based on the national lightning detection network(NLDN) Compare ground and airborne noise Compare airborne E-field and H-field noise

Data Collection System Overview

Ohio University Avionics Engineering Center Airborne Data Collection Equipment Aircraft –King Air C-90B –Pressurized twin turboprop –240 knot cruise speed Equipment –Novatel OEM4 GPS receiver –LORADD-DS DataGrabber –WX-500 StormScope –Apollo 618 –Data collection PC

Ohio University Avionics Engineering Center Data Collection Equipment Pre-amp Data Collection PC WX-500 StormScope Whip antenna (e-field) ADF antenna (h-field) Stormscope antenna GPS antenna Apollo 618

Ohio University Avionics Engineering Center Data Collection PC CyberResearch dual backplane with 933MHz P-III CPU cards 512MB RAM 160GB of hard-drive space

Ohio University Avionics Engineering Center WX-500 Stormscope RS-232 data output 200nmi range Heading stabilization Data will be used in conjunction with National Lightning Detection Network (NLDN) data

Ohio University Avionics Engineering Center Loran-C H-Field vs. E-Field Antennas Large effective height –Little voltage amplification needed High impedance (M  ) –Charge build-up (cannot be terminated) Antenna phase pattern is omnidirectional Whip or wire antenna Small effective height  Large voltage amplification needed (low noise pre-amp) Low impedance (1W)  No charge build-up (antenna is grounded) One loop creates 0 and 180 degrees. Conformal antenna E-Field (Electric) H-Field (Magnetic)

Ohio University Avionics Engineering Center Aircraft Data Collection Equipment

Ohio University Avionics Engineering Center Antennas E-Field II Morrow A-16 H-Field King Radio KA42A

Ohio University Avionics Engineering Center Rackmount chassis for data collection equipment LORADD-DS DataGrabber DC Power Supply AC in GPS H-field E-field GPS antenna LAN Novatel GPS Receiver Antenna Interface Antenna Interface

Ohio University Avionics Engineering Center LORADD-DS DataGrabber Sampling rate: 400kHz Resolution: 16 bits Dynamic range: 96dB Two input channels – sampled simultaneously Differential input amplifiers for the antennas TCP/IP data output Clock stability: 1ppm

Ohio University Avionics Engineering Center Antenna Interface Boxes Adjust received signal level Provide interference isolation for the antenna cable Impedance matching for the DataGrabber antenna inputs

Ohio University Avionics Engineering Center Novatel GPS Receiver 1-20 Hz position data Time synchronization RS-232 data output (ASCII or binary)

Ohio University Avionics Engineering Center Lab Data Collection Equipment LORADD-DS DataGrabber –400kHz sampling –Dual channel Data collection PC

Ohio University Avionics Engineering Center Antennas E-field –IIMorrow A-16 Whip antenna with integral preamplifier/impedance transformer –Powered by an Apollo 618 LORAN receiver

Ohio University Avionics Engineering Center Antennas H-field –King KA42A ADF Loop antenna –Requires a separate preamplifier/impedance transformer tuned to the LORAN-C band –Powered by 5-10VDC

Ohio University Avionics Engineering Center Initial Data Collection Results The next 2 slides show screen captures from the initial lab data collection test using both antennas Channel 1: h-fieldChannel 2: e-field Screen capture 1 shows the RF data from each antenna –The presence of the LORAN signal can be seen in each channel –E-field channel (bottom) has more amplification than h-field (this does not affect the SNR) Screen capture 2 shows the spectrum of the RF data –The filter bandwidth around 100kHz is apparent –Several CW interference sources are evident

Ohio University Avionics Engineering Center

Example of collected data: Time domain

Ohio University Avionics Engineering Center

Example of collected data: Spectrum

Current Status of the Data Collection Task

Ohio University Avionics Engineering Center Airborne Collected Data “Clear” – 10hrs Overcast – 4hrs Close t-storm (<20nmi) – 20min Nearby t-storm – 2hrs Other – 4+hrs

Ohio University Avionics Engineering Center Data Collection Flight Tracks

Ohio University Avionics Engineering Center Thunderstorm Data Conditions

Ohio University Avionics Engineering Center

Future Work Continue data collection effort –Varying environmental conditions –Different locations –Correlate National Lightning Detection Network (NLDN) data –Mobile ground data collection equipment Calibrate the DataGrabber Aircraft noise analysis

Ohio University Avionics Engineering Center Acknowledgements Mitch Narins (FAA) Wouter Pelgrum (Reelektronika) Bryan Branham (Ohio University) Jay Clark (Ohio University)

Questions?