Transcript EMP and the Radio Amateur

What it is, what it does,
how to protect your station
Rick Blasco, NX6R
What is EMP?
• ElectroMagnetic Pulse caused by:
– Lightning
– Geomagnetic storm
– Power line transient
– Thermonuclear detonation
– E-bomb
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What is EMP?
• ElectroMagnetic Pulse caused by:
– Lightning
– Geomagnetic storm
– Power line transient
– Thermonuclear detonation
– E-bomb
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Lightning
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Lightning
• Weak “tracer” pulse cloud to ground,
followed by strong “return” pulses ground
to cloud
• 3-4 pulses or “strokes” per “flash” or
“strike”
• Peak current 3 kA to 175 kA (18 kA typ)
• Spectrum falls off more rapidly than
thermonuclear
crossover 1-10 MHz
Dennis Bodson [3] and Ron Block KB2UYT [4] and in QST
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Thunderstorm days per year
Ron Block KB2UYT in QST [4]
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Strikes per year vs. tower height
Ron Block KB2UYT in QST [4]
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Thermonuclear
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Thermonuclear
• Compton effect: gamma rays interact with
atmosphere to produce EMP
• Can cover large geographic area
• Less likely to occur than other sources
• EMP probably “least of your worries”
• Three “strokes” of EMP
Dennis Bodson W4PWF in QST [3]
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E1 and E2 pulse propagation
Dr. John Foster, et al. 1994 EMP Threat Assessment Report [5]
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E3 pulse propagation
Dr. John Foster, et al. 1994 EMP Threat Assessment Report [5]
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EMP propagation vs altitude
Dennis Bodson W4PWF in QST [3]
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E-bomb
"Gort! Klaatu barada nikto!"
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E-bomb
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Localized EMP effect
Cheap to make ($1000-$2000)
Commonly available materials
Well-known technology (since 1940s)
Multiple delivery methods
Peak current of large device stronger than
lightning stroke
Carlo Kopp in Air & Space Power Journal [1]
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“Ideal” terrorist weapon
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Highly disruptive if properly placed
Minimum “collateral” damage
Cheap to make
Commonly available materials
no need to smuggle into country
• Conventional C-4 plastic explosive
impossible to detect from a distance
• Can be fitted in a van and driven to target
site
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Coaxial Flux Compression Generator (FCG)
Carlo Kopp in Air & Space Power Journal [1]
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Virtual Cathode Oscillator (VIRCATOR)
Carlo Kopp in Air & Space Power Journal [1]
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Characteristics of an EMP pulse
• Extremely high energy
• Very short duration
→
Energy in RF spectrum
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Pulse shapes
Carlo Kopp in Air & Space Power Journal 1996 [1]
Approximate Spectrum of EMP
Dennis Bodson W4PWF in QST[3]
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What it does
• Presents high voltage and high current to:
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Antennas
Transmission lines
Rotor cables
Power cables
Microphone and other external cables
Internal equipment wiring
PC board traces
Semiconductor junctions
(diodes, transistors, ICs)
– Vacuum tubes
– Passive components
(capacitors, resistors, inductors, etc.)
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Will it move?
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Will all this stuff work?
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Will you have acce$$?
“We should have left it buried in the backyard.”
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If it can arc, smoke, or melt …
IT CAN FRY!
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How it does it
• Conduction
– Antenna system
– Power lines
– Ground connection
• Induction
– Cables and wires act as antennas
– Coils, chokes, and transformers act as voltage
generators
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Larry Scheff W4QEJ in February 2008 QST [2]
Ohm’s Law (DC)
E
I R
P
E I
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Ohm’s Law (RF - simplified)
V
I
rf
I
rf
rf
L
2πf
V
rf
c
2πf
2π = 6.283185307
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Ohm’s Law (RF - simplified)
P
P
rf
I
2
rf
2
rf
L
V
rf
2
c
2
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Protection (hardening) techniques
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Disconnect external cables
“Stout” grounding
Transient suppressors
Energy-tolerant components
Faraday cage / shielding
Ron Block KB2UYT in QST [4]
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“Stout” Grounding
Ron Block KB2UYT in QST [4]
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“Stout” Grounding
• Common “bulkhead” ground point
“single-point ground panel”
• Suppressors external to building
keep the strokes outside!
• Multiple ground rods interconnected with #6
or larger wire per National Electrical Code
Ron Block KB2UYT in QST [4]
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Lightning suppressors
Ron Block KB2UYT in QST [4]
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Modified Faraday Cage
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Steel file cabinet
Add steel plate to close bottom
Single connection to ground
Energy flows around the faraday “shell” to ground
Good shielding below 10 MHz
Add shielding gaskets around drawers for
protection to VHF/UHF
• Store spare equipment, microphones, antennas,
coax, and cables for use after “attack”
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Other measures
• Reduce inductance of ground connections
large diameter wire or copper flashing 1”-3” wide
• Multiple length parallel wires to ground rods
avoid odd λ/4 multiples throughout spectrum
• Shorten length between power line suppressors
and equipment
• Coil cables
keep ends separated
• Optical fibre
• Optical storage (CDs and DVDs)
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Ohm’s Law (RF - simplified)
V
I
rf
I
rf
rf
L
2πf
V
rf
c
2πf
2π = 6.283185307
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Other measures
• Reduce inductance of ground connections
large diameter wire or copper flashing 1”-3” wide
• Multiple length parallel wires to ground rods
avoid odd λ/4 multiples throughout spectrum
• Shorten length between power line suppressors
and equipment
• Coil cables
keep ends separated
• Optical fibre
• Optical storage (CDs and DVDs)
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References
1.
2.
3.
Kopp, Carlo “The Electromagnetic Bomb - a Weapon of Electrical Mass Destruction”, Air
& Space Power Journal 1996
Scheff, Larry W4QEJ “Lightning: Understand It or Suffer the Consequences” QST
Parts 1-2: February, March 2008
Bodson, Dennis W4PWF “Electromagnetic Pulse and the Radio Amateur” QST
Parts 1-4: August, September, October, November 1986
condensed from “Electromagnetic Pulse/Transient Threat Testing of Protection Devices for Amateur/Military Affiliate
Radio System Equipment” National Communication Systems Report NCS TIB 85-10
4.
5.
6.
Block, Ron KB2UYT “Lightning Protection for the Amateur Station” QST
Parts 1-3: June, July, August 2002
Foster, Gjelde, Graham, Hermann, Kluepfel, Lawson, Soper, Wood, and Woodard
“Report of the Commission to Assess the Threat to the United States from
Electromagnetic Pulse (EMP) Attack” 2004, commissioned by Public Law 106-398, Title
XIV, §1402
Tracy, Mike KC1SX “Lightning Protection” QST Lab Notes
Parts 1-2: October, December 1994
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