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

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LORAN-C Band Data Collection Efforts atOhio
UniversityPresented by Curtis Cutrightto the
International LORAN Association32nd Annual
Convention andTechnical Symposium Boulder, CO
November 6, 2003
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Outline

• Task overview
• Data collection system overview
• Airborne data collection equipment
• Lab data collection equipment
• Initial data collection results
• Task progress

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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

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Purpose

• Develop threat models for aircraft in flight
• Precipitation static (p-static)
• Atmospheric noise
• Man-made noise(cross rate, CW)
• Lightning

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Purpose

• Identify all trade-offs for E and H-field
  antennas, SNR, phase error, saturation, bandwidth

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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

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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

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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

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Data Collection SystemOverview
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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

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

• CyberResearch dual backplane with 933MHz P-III
  CPU cards
• 512MB RAM
• 160GB of hard-drive space

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WX-500 Stormscope

• RS-232 data output
• 200nmi range
• Heading stabilization
• Data will be used in conjunction with National
  Lightning Detection Network (NLDN) data

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Loran-C H-Field vs. E-Field Antennas
E-Field(Electric)
H-Field(Magnetic)

• Large effective height
• Little voltage amplification needed
• High impedance (MW)
• 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

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Aircraft Data Collection Equipment
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Antennas
E-Field II Morrow A-16
H-Field King Radio KA42A
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Rackmount chassis for data collection equipment
AC in
DC Power Supply
LORADD-DS DataGrabber
GPS
GPS antenna
Novatel GPS Receiver
LAN
Antenna Interface
Antenna Interface
H-field
E-field
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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

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Antenna Interface Boxes

• Adjust received signal level
• Provide interference isolation for the antenna
  cable
• Impedance matching for the DataGrabber antenna
  inputs

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Novatel GPS Receiver

• 1-20 Hz position data
• Time synchronization
• RS-232 data output (ASCII or binary)

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Lab Data Collection Equipment

• LORADD-DS DataGrabber
• 400kHz sampling
• Dual channel
• Data collection PC

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Antennas

• E-field
• IIMorrow A-16 Whip antenna with integral
  preamplifier/impedance transformer
• Powered by an Apollo 618 LORAN receiver

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Antennas

• H-field
• King KA42A ADF Loop antenna
• Requires a separate preamplifier/impedance
  transformer tuned to the LORAN-C band
• Powered by 5-10VDC

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Initial Data Collection Results

• The next 2 slides show screen captures from the
  initial lab data collection test using both
  antennas
• Channel 1 h-field Channel 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

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Example of collected data Time domain
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Example of collected data Spectrum
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Current Status of the Data Collection Task
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Airborne Collected Data

• Clear 10hrs
• Overcast 4hrs
• Close t-storm (lt20nmi) 20min
• Nearby t-storm 2hrs
• Other 4hrs

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Data Collection Flight Tracks
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Thunderstorm Data Conditions
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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

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Acknowledgements

• Mitch Narins (FAA)
• Wouter Pelgrum (Reelektronika)
• Bryan Branham (Ohio University)
• Jay Clark (Ohio University)

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Questions?