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Author Topic: EMP Protection, Snap On Ferrites, Supressors, Etc  (Read 367 times)

ROYSBOY

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EMP Protection, Snap On Ferrites, Supressors, Etc
« on: October 19, 2021, 04:01:12 PM »

Didn't know where to put this, seems like the most logical place.

Not so much from a HF (have that squared away) perspective but from a breaker panel, auto and generator angle.

I see people selling snap on ferrite cores for incoming house main feeds that snap on the incoming lines, 3 required. They also sell the same for battery cables, along with other means of protection devices for autos, a thing called a trap that plugs into your cig lighters.

They market these things as a "special, or modified" ferrite core with a specific mix, they sell them for $49.00 each. I know things are getting expensive but isn't this a tad high for a snap on?

From what I've been able to research, the core mix needs to be able to stop a few thousand volts (up to 5000) in the 0-300-400mhz range for less than a nano second for the first E1 wave, E2 less voltage/slightly longer, E3 less voltage than E2, could last much longer, minutes or even hours, depending... Naturally, it needs to be of high permeability and not saturate for that short period of time for the E1, the most damaging.

There has to be a less expensive option than what they are selling. Still, I wonder about the effectiveness and also if they are selling these for such a high price out of peoples fear.

I think the most I have ever paid for a ferrite of any type/shape or mix was around $15.00. This lead me to wonder, just what "special" mix they are using and if using these snap on cores to clamp this kind of voltage isn't snake oil at best.

I see EMP's as unknowns orbiting variables and difficult to protect against

Any opinions?
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W1VT

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Re: EMP Protection, Snap On Ferrites, Supressors, Etc
« Reply #1 on: October 19, 2021, 04:30:26 PM »

http://www.arrl.org/lightning-protection

Electromagnetic Pulse and the Radio Amateur - Part 1
QST August 1986, pp. 15-20, 36
Will your station survive the effects of lightning strikes ........
Electromagnetic Pulse and the Radio Amateur - Part 2
QST September 1986, pp. 22-26
...testing EMP/transient-protection devices
Electromagnetic Pulse and the Radio Amateur - Part 3
QST October 1986, pp. 38-41
...protectors are connected to Amateur Radio equipment and retested.
Electromagnetic Pulse and the Radio Amateur - Part 4
QST November 1986, pp. 30-34
What can be done to protect an Amateur radio station from lightning......
Feedback: QST February 1987, p. 43
Feedback: QST April 1987, p. 59
The model number of the Siemans spark gap is B1-A350, not BI-A350.
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W9IQ

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Re: EMP Protection, Snap On Ferrites, Supressors, Etc
« Reply #2 on: October 19, 2021, 05:48:26 PM »

There is no ferrite mix such that three snap on cores on a powerline will provide meaningful EMP protection. One hardly has to break out a calculator or spreadsheet to come to that conclusion. But then the buyers of such devices are probably also stockpiling sliderules.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

K0UA

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Re: EMP Protection, Snap On Ferrites, Supressors, Etc
« Reply #3 on: October 19, 2021, 08:17:20 PM »

I prefer the circular slide rules rather than the stick type.  You are never off scale with a circular one. And If I really looked for them I have a couple of them. somewhere.   :)
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73  James K0UA

KH6AQ

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Re: EMP Protection, Snap On Ferrites, Supressors, Etc
« Reply #4 on: November 01, 2021, 03:18:16 PM »

I would look at MIL-STD-188-125-1 and MIL-HDBK-423. And the document below.


Electromagnetic Pulse (EMP) Protection and Resilience Guidelines for Critical Infrastructure and Equipment

https://www.cisa.gov/sites/default/files/publications/19_0307_CISA_EMP-Protection-Resilience-Guidelines.pdf
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W9IQ

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Re: EMP Protection, Snap On Ferrites, Supressors, Etc
« Reply #5 on: November 01, 2021, 03:50:32 PM »

I have always viewed the CISA EMP document skeptically since it contains assertions such as:

Ferrites effectively introduce a complex impedance onto the cable. There is signal attenuation
because:
• Impedance mismatch relative to the normal cable impedance means some signal is
reflected back down the cable,
• And the imaginary part of the impedance means that energy is absorbed.

Simply cringe worthy...

Since it is declassified, perhaps it is really counter-intelligence for the enemy?

- Glenn W9IQ
« Last Edit: November 01, 2021, 03:57:40 PM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.
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