A Lowcost but yet Sciencegrade ELFVLF Receiver

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A Low-cost but yet Science-grade ELF/VLF Receiver

• Total System Cost (including labor) is less than
  3K
• Two ELF/VLF channels sampled at 100-kHz and
  16-bit resolution
• System sensitivity allows measurements of sub-pT
  fields - truly science grade data
• Both narrowband and broadband measurements are
  possible

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VLF Data from Firat University in Elazig, Turkey
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Natural and HAARP-injected ELF/VLF Signals
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Antenna, Preamp Line Receiver
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System Sensitivity
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Computer and Line Receiver
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Typical System Setup (Inside)
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Preamplifier Box Open
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Preamplifier Box Closed
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Line Receiver Front
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Line Receiver Front
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Line Receiver Guts
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GPS Antenna Card
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Small Triangular Antenna and Preamplifier
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Dummy Loop Antenna for Calibration
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VLF Sensing of Ionospheric Disturbances over
Europe
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VLF Data from Firat University in Elazig, Turkey
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Natural and HAARP-injected ELF/VLF Signals
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Stanford Program at Palmer Station, Antarctica
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Lightning-generated Whistlers

• Very Low Frequency (VLF) waves launched by
  lightning propagate in the Earth-ionosphere
  waveguide (vpc)
• Wave energy also couples upward to the radiation
  belts, propagating along
  filamentary ducts of
  enhanced ionization
• The magnetospheric plasma is a dispersive slow
  wave medium (vp0.01 c)
• Signal arriving at the
  conjugate region sounds like a whistler

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The Science of the VLF Receiver
Stuff We Care About
Storage Media
VLF Receiver
Antenna
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The Art of the VLF Receiver

• Ultra Sensitive/Low Noise
• Broadband
• Precision Timing/Phase Accuracy
• Reliable
• Easy to Build, Set-up, Use, Repair
• Fully Documented
• Low Cost

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The Starting Line

• HAIL/HAARP Receiver
• Problems
• Outdated parts
• Failed too often
• Size and construction
• Expensive GPS clock
• Designed for narrowband
• Incomplete documentation
• Unnecessarily complicated

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The VLF Groups Needs

• Repair existing receivers
• Redesign receiver
• Build, test, deploy
• Deploy
• Deploy
• Deploy
• Deploy

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Enter Solar Physics Group

• CISM Educational Outreach
• Professor Phil Scherrer
• High School Outreach
• Low Cost
• Easy to Use
• Dual use system
• Daytime monitor solar activity
• Nighttime monitor VLF

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Antenna Design

• B-Field, Magnetic Loop
• Orthogonal Pair
• 1.0 O, 1.0 mH
• Various sizes
• Cuts off at 318 Hz

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Preamplifier

• Impedence matched
• Paschal amplifier
• 3 cutoff modes
• Gain selectable
• Calibration circuit
• Weatherproof

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Preamp to Line Receiver

• Long cabling
• Belden 1217B
• Four twisted pairs, shielded
• Provides /- 15V
• Calibration enable
• Line Transformer
• Stancor A-4096
• Better low frequency response

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Line Receiver

• Power supply
• PowerOne Had15
• Anti-aliasing filter
• GPS synchronization

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Anti-Aliasing Filter

• LTC1562
• 12th order lowpass
• Elliptical filter
• 47 kHz cutoff
• 100dB attenuation at 55 kHz
• 50 us relative delay

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Line Receiver GPS

• Motorola M12 OnCore
• Provides 1 PPS signal
• 200 ns accuracy
• FPGA generates 100 kPPS
• Divides down 10 MHz
• Feedback trims block
• Time synched to 1 PPS
• 100 ns maximum draft
• Phase error 2.7 at 25 kHz

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Digitizing

• National Instruments 6034E
• Plugs into PCI slot
• PCMCIA laptop version available
• 200 kS/second, 16-bit
• 100 kHz sampling each channel

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The Big Picture
B-Field Antenna
GPS Antenna
Computer
Long Cable
Line Receiver
Analog to Digital
Preamp
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Software

• Two channel narrowband/broadband
• Adapted from Robb Moores software
• Daily schedule
• Works in conjunction w/Matlab

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Dummy Loop

• 1.0 O, 1.0 mH
• Two inputs/outputs
• Useful for calibration
• Takes minutes to build

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Calibration

• 8.1592 MHz clock
• PIC generates random sequence
• Applied to front end
• Output series of frequency spikes

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WHY ISNT IT WORKING?
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Bumps in the Road

• Schematic/layout errors
• Acquiring parts
• Preamp box
• Line transformers
• GPS failure
• Anti-aliasing troubles
• ADC triggering

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The Immaculate VLF Reception
July 21, 2004, 4PM, Packard roof
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The Immaculate VLF Reception V2
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System Testing

• Packard 012 - June
• Packard roof July
• Stanford Dish August
• Puerto Rico August
• Alaska September

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Lightning(Whistler)-Induced Electron
Precipitation
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VLF Remote Sensing of Lower Ionospheric
Disturbances
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(No Transcript)
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Holographic Imaging of the Lower Ionosphere
VLF receivers at 13 high schools Provides
excellent opportunities for outreach