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Author Topic: EMP from North Korea's nuke over the Pacific, would it damage radios?  (Read 8831 times)
AF6LJ
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Posts: 372




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« Reply #15 on: September 26, 2017, 07:25:38 AM »

MIL-STD-188-125-1 provides design parameters for EMP hardened equipment. Also see MIL-HDBK-423.

The E-field level to design antenna systems to is 50kV/m. http://ema3d.com/high-altitude-electromagnetic-pulse-hemp-emp-simulation/

The question "How long of a wire do you need to generate 2KV?" For an open-circuit monopole the wire length would be 3.7 cm or 1.5 inches.

So If I have this right, it would take a very short piece of wire to develop voltages that would kill an IC , correct?
It's more complicated than that.
The current is very low, capacitance in the circuit will absorb much of the energy, many factors are at play.
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Sue,
AF6LJ
KH6AQ
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« Reply #16 on: September 26, 2017, 08:40:43 AM »

Take a look at this NEMP simulator.   http://morens.co.kr/board/upload/nemp_systems_ts_nemp.pdf
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AF6LJ
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« Reply #17 on: September 26, 2017, 08:49:44 AM »

50KV per meter squared isn't much energy and we need to remember that in an actual nuclear explosion the emp energy decreases at the rate of one ninth every time the distance from the device is doubled.
If a receiver has a DC short on the input or the antenna presents a DC short the effects of the EMP entering from the input side of the receiver are almost nullified.
The real danger is and always has been due to long lines, power telephone and long / large antennas, with the notable exception of AM broadcast radios the ferrite loop antenna contained therein would potentially couple enough energy to damage the radio. .
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Sue,
AF6LJ
KD0REQ
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« Reply #18 on: September 26, 2017, 08:50:20 AM »

the most critical element is the grid.  if the grid survives, we can make more stuff, pump more water, process more food.

no grid, no milking machines, computers, water works, Tesla cars, broadcasting, military base readiness, gas and diesel pumps on the corner ....

it basically comes down to will the transformer insulation puncture, insulators carbon-track, relays fail, SmartGrid control systems fizzle out. EMP is a widespread multiple lightning strike, all at once. we will be in deep doo.

oh, and there is no Big Chief over power distribution and generation to pick up the phone and say, "fix this now, hang the cost, for tomorrow the Norks may test us."

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AF6LJ
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« Reply #19 on: September 26, 2017, 09:25:32 AM »

the most critical element is the grid.  if the grid survives, we can make more stuff, pump more water, process more food.

no grid, no milking machines, computers, water works, Tesla cars, broadcasting, military base readiness, gas and diesel pumps on the corner ....

it basically comes down to will the transformer insulation puncture, insulators carbon-track, relays fail, SmartGrid control systems fizzle out. EMP is a widespread multiple lightning strike, all at once. we will be in deep doo.

oh, and there is no Big Chief over power distribution and generation to pick up the phone and say, "fix this now, hang the cost, for tomorrow the Norks may test us."
There is no lightning involved; you are right about the grid, I would hope that our government would have the good sense to warn power companies of an inbound nuke. They could shut down the grid, open relays and potentially save a lot of hardware from damage.


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Sue,
AF6LJ
KH6AQ
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« Reply #20 on: September 26, 2017, 10:06:49 AM »

This Montena technical note points out the the E-field during IEC 61000-4-2:2008 ESD testing is similar to that of a NEMP event. See 3.2, Comparison with ESD.

http://www.montena.com/fileadmin/technology_tests/documents/technical_notes/TN17F_Safe_distance_NEMP.pdf

I believe the 50 kV/m used for NEMP design is assumed to be at ground level, far from the nuclear event. BTW, in free space the E-field decreases linearly with distance while the energy decreases as distance squared. Double the distance and the E-field is 1/2 while the energy is 1/4.

Wikipedia has an interesting article on this subject. https://en.wikipedia.org/wiki/Electromagnetic_pulse
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AF6LJ
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« Reply #21 on: September 26, 2017, 10:28:35 AM »

This Montena technical note points out the the E-field during IEC 61000-4-2:2008 ESD testing is similar to that of a NEMP event. See 3.2, Comparison with ESD.

http://www.montena.com/fileadmin/technology_tests/documents/technical_notes/TN17F_Safe_distance_NEMP.pdf

I believe the 50 kV/m used for NEMP design is assumed to be at ground level, far from the nuclear event. BTW, in free space the E-field decreases linearly with distance while the energy decreases as distance squared. Double the distance and the E-field is 1/2 while the energy is 1/4.

Wikipedia has an interesting article on this subject. https://en.wikipedia.org/wiki/Electromagnetic_pulse

So we don't actually know critical details.
A friend is a nuclear engineer, we had a long discussion on this subject and tried to find out critical details  and it appears many of the critical details are ether not on the net or classified.

the EMP from a nuke is caused by the Compton Effect Neutrons ionize the atmosphere giving it an electrical charge.
This electrical charge while high in voltage potential is very low in current.

It would be nice to have all the data in order to form an educated guess as to what would happen. What we hear on the lamestream media is there to gather ratings and fear monger, I am sure of that.

I am not saying there is nothing to be worried about, I am saying I feel the threat is overstated.
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Sue,
AF6LJ
W9IQ
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« Reply #22 on: September 26, 2017, 11:13:20 AM »

With regard to HEMP events, radios with no cords connected, no internal antennas, and with metal cabinets will probably not be affected at all. Cords, antennas, power lines, etc. will collect the EM energy from an HEMP event and therefore should ideally be disconnected from the radio to afford the best protection. By way of an example, an 80 meter HF antenna has the potential to generate a 1 MV signal. Incidentally, coax feedline provides superior EMP protection compared to ladder line due to its shielding of the center conductor from EMP events and due to its lower arc over voltage that provides a level of additional protection for any connected equipment.

Due to the very short pulse duration from an HEMP event, it is estimated that the energy at the ground level will be < 1 J/m2. This means than many typical transient protection products will not be destroyed by the event and may therefore provide reasonable protection if properly applied.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KH6AQ
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Posts: 7718




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« Reply #23 on: September 26, 2017, 11:20:06 AM »

Good information Glenn.

This white paper by PolyPhasor shows a range of NEMP voltages and currents for HF antennas. The range is 10kV to 1MV and 500A to 10kA. That's 5-10,000 megawatts. As a point of reference, an 8kV human body model discharge into a transceiver antenna port is 5 amps for roughly 100ns. The peak ESD power into a 50 ohm load is 1250 watts.  

http://www.transtector.com/SiteMedia/SiteResources/WhitePapersandTechnicalNotes/1485-041.pdf?ext=.pdf
« Last Edit: September 26, 2017, 11:31:29 AM by KH6AQ » Logged
AF6LJ
Member

Posts: 372




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« Reply #24 on: September 26, 2017, 11:45:11 AM »

With regard to HEMP events, radios with no cords connected, no internal antennas, and with metal cabinets will probably not be affected at all. Cords, antennas, power lines, etc. will collect the EM energy from an HEMP event and therefore should ideally be disconnected from the radio to afford the best protection. By way of an example, an 80 meter HF antenna has the potential to generate a 1 MV signal. Incidentally, coax feedline provides superior EMP protection compared to ladder line due to its shielding of the center conductor from EMP events and due to its lower arc over voltage that provides a level of additional protection for any connected equipment.

Due to the very short pulse duration from an HEMP event, it is estimated that the energy at the ground level will be < 1 J/m2. This means than many typical transient protection products will not be destroyed by the event and may therefore provide reasonable protection if properly applied.

- Glenn W9IQ
Agreed;
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Sue,
AF6LJ
AA4HA
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Posts: 2384




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« Reply #25 on: October 10, 2017, 03:56:00 PM »

Where it gets funky is in the fast rise times and that NEMP is not a single waveform;

The first and fastest waveform has a rise time of about 2 nSec and a duration of between 20 and 80 nSec. This is known as the "E1 waveform" and is potentially the most damaging to solid state electronics. The rise time is so fast that the lead lengths of transient suppressors and their trigger time (like with GDT's (gas tubes) has not even happened before the most energetic part of the E1 waveform has come and gone (up to 50 kV/m for close in). E1 is produced by the prompt-gammas of a detonation.. the gamma rays interact with the Earth's magnetic field and creates Compton electrons that bend and produce transverse currents.

E1 Waveform discussion;     http://www.eiscouncil.com/App_Data/Upload/9b03e596-19c8-49bd-8d4e-a8863b6ff9a0.pdf

As the E1 waveform is decreasing now the scattered gamma rays and gammas produced by neutron interactions are produced. This is known as the E2 pulse and can be several hundred milliseconds long.

Lastly is E3. This is a distortion of the Earth's magnetic field and can last for tens of seconds. It is a magnetohydrodynamic effect and can be the most problematic for long lines (telephone and power) and transformers in substations.
-----------
I had a client where this understanding was required for an electrical utility. We had to become familiar with the Oak Ridge report on the vulnerabilities of the electrical power grid.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
Free space loss (dB) = 32.4 + 20 × log10d + 20 × log10 f
N8FVJ
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« Reply #26 on: October 13, 2017, 08:08:18 AM »

The test was underground, no EMP was passed into the atmosphere plus it was on the other side of the earth.
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