Electromagnetic Pulse

bmet

Re: Electromagnetic Pulse

I've stood in front of a F-4 Fire Control radar when it was activated, and the sweep of WARMTH thru my body was just as scary as the spinning-radome tracking back and forth across my vision. I was painted 3 times before I realized, and ran away from the nose of the jet.

The dumb 3-level who turned the radar on was given an LOR for violating safety tech order.

XRinger

Re: Electromagnetic Pulse

SteveK wrote: »

According to some highly respected sources 2012 is gonna be a busy solar flare and sun spot year.

Looking forward to the sunspots for Amateur Radio band improvement. Not so much the flares...

I hold a radio in reserve like I do the other things like my signature below.

Wasn't a quarter of Canada knocked out relatively recently from solar storms? It's enough reason for me to be a true believer:roll:

I think that's wishful thinking on someone's part. Cycle 24 has been a bust, since it started.

http://solarscience.msfc.nasa.gov/predict.shtml

If you look at the Cycle 23 peak in 2000~2001, add 11 years, we should be right in the middle of the Cycle 24 peak..

That predicted peak marked in red is a joke..

http://www.swpc.noaa.gov/SolarCycle/

Our next chance for a good peak seems like 2022-2023 (I should live so long)..

Just a guess, but it seems like #24 isn't going to get over a 50 count.
I think we are actually right in the middle of #24 right now, and a 25 count just might be as good as it gets.

73,
Rich

bmet

Re: Electromagnetic Pulse

biorhythms aren't an exact science

SteveK

Re: Electromagnetic Pulse

Indeed, this last cycle lasted an extra 2+ years, who would have thought?

Keeping in mind the previous prediction. This cycle was predicted to be as active as the past and now it is going to rival the Dalton Minimum? Makes me wonder about the actual process of solar prediction entirely. Not needing to mention here, known ice chunks shearing off essential insulation upon launch of the Shuttle....

So OK, I'll be alright with a radio in reserve and won't expect too much good tx/rx from the other radios in service. It looks like the cell phones will continue to work reliably which is good. I'll keep my stash though as an insurance policy I think.... Wish I'd have done that with much more of my investments not so long ago...

niel

Re: Electromagnetic Pulse

stevek,
if an emp enhanced nuclear device is detonated, it could wipe communications for half of the country. odds are they will have more than one to detonate too. this type of emp is not limited to wiping ground communications either as satellites will also be wiped making satellite phones totally useless. anyway, most will not store for such an event and you most likely won't have anybody to talk to even if given band conditions returning some. now on the long shot you do find somebody on, they will most likely be in the same circumstance as you and will not be able to help you or for you to help them making the extra effort to store the stuff a bit of an exorcise in futility.

lightning emp is a realistic concern to prepare for and is more localized.

SteveK

Re: Electromagnetic Pulse

Hi Niel,

It wasn't me that recapped their preparedness for a nuclear EMP strike. I don't recall who it was but if it makes them feel better I don't see any harm.

Without getting too far off-topic I belong to a religion that heavily promotes preparedness for all things possible. I suspect this approach is formed from past experiences and some colorful imagination to boot.

I can imagine being in an area cut-off from communications with the outside world. I can imagine long term food shortages and communities trying to cope with this. A little bit of renewable energy and a way of listening to possibilities via Ham could be a valuable tool.

Remember, the folks in Katrina saw the benefit of Amateur radio. Operators were solicited from all over the USA in order to support that effort. The Gov't was at a major dissadvantage in this regard.

I feel my Faraday Cage and the items inside are as prudent as a savings account or investment portfolio what with the minimal cost it has burdened us with.

We have faaaar more dollars in food storage.....freaky eh?

niel

Re: Electromagnetic Pulse

ok, my mistake, but to all out there there is a point you reach where the effort to prepare can be futile.

russ

Re: Electromagnetic Pulse

The Martians are coming! The Martians are coming!

Just wear a tinfoil hat and underwear - no problem.

James

Re: Electromagnetic Pulse

bmet wrote: »

except that aluminum foil is not all aluminum, no real benefit other than dust cover. A better 'foil', is that material used for radiant heat barrier in your attic, giving two advantages in the same wrapping.

I respectfully disagree...modern aluminum foil is over 90% aluminum, an very good electrical conductor and almost as good as copper mesh shielding.

From what I've read, it might actually be better than steel when used as a Faraday Cage.

Also, most heat barrier insulation you refer to is plastic with aluminum coating. So are the mylar party balloons.



http://www.aluminum.org/Content/NavigationMenu/TheIndustry/Foil/default.htm

SteveK

Re: Electromagnetic Pulse

Aluminum foil (like Reynolds) may be of a good enough composition but is far too thin to be effective. Steel works fine as most sheets are thick enough for this. It is what the earliest engineers used to protect their equipment.

I use copper mesh and copper strapsfor a electrically seamless enclosure but it is pricey. Find it here: http://www.twpinc.com/twpinc/products/CATALOG1/TWPCAT_11

Here is more info that chicken little reccomended to me...:cool:

http://www.tpub.com/content/NAVFAC/hdbk419a_vol2/hdbk419a_vol20186.htm

Governments around the globe are "sheilding-up". Are you?

XRinger

Re: Electromagnetic Pulse

russ wrote: »

The Martians are coming! The Martians are coming!

Just wear a tinfoil hat and underwear - no problem.

Are you sure it's Martians? I heard it was Global Warming..

SteveK

Re: Electromagnetic Pulse

XRinger wrote: »

Are you sure it's Martians? I heard it was Global Warming..

Time to rustle up more speedos!!...:roll:

James

Re: Electromagnetic Pulse

SteveK, Thanks for the links for the copper mesh.
I've visited a few semi-scientific website and they seem to think that the thickness is not an issue. Have you done some first hand testing? I do question some of the website info due to the "survivalist" theme of their website. In most cases those sites offer re-hashed and non-scientific advise. For those of us on a tight budject, would you think multi-layered aluminum foil would suffice especially if stored in a steel container?
Sounds like you might have real experience.

I tried the old low-tech test of turning on a radio and wrapping with foil...the signal was absent.(not recieving)
Thanks

XRinger

Re: Electromagnetic Pulse

Since I work with microwave stuff at work, and worry about shielding,
I've done some simple experiments with a Faraday cage that can be found in most kitchens.

You can try this with Cell phones, cordless phones, pagers and even UHF Walkie Talkies.

Turn it on, place it inside the microwave oven, and call it..

I don't know why, but I've tested three different microwave ovens using
a 915 mHz pager and/or cell phones and the signal gets inside the oven..

Be careful not to let anyone Press the Cook button..

I've looked at the seals on the doors, and they look fine. I guess the RF is
getting in to the air ventilation port..?.

These are relatively weak signals.. So, IMHO, blocking out really strong RF/EMP signals isn't real easy..

mike95490

Re: Electromagnetic Pulse

XRinger wrote: »

...
I don't know why, but I've tested three different microwave ovens using
a 915 mHz pager and/or cell phones and the signal gets inside the oven.. ....

Maybe because the oven is only a shield at 2.5GHz, not a broadband cage?

john p

Re: Electromagnetic Pulse

For what its worth . All millitary vehicles use copper mesh around the communications centre, its effectiveness???? its just how its been done since WW2 ..I know as have worked on many such vehicles for the army over a period of many years.
having said that I have serious doubts its all that effective as I have never had that much loss of signal for my cell phone

I really dont think there is a great deal of successful shielding you can do with consumer electronics.despite all the advice given
Millitary grade ICs are designed to withstand considerable impulses,
its not even possible to make a tank totally proof against electromagnetic pulses, but cant tell you why.

XRinger

Re: Electromagnetic Pulse

mike90045 wrote: »

Maybe because the oven is only a shield at 2.5GHz, not a broadband cage?

Well, I'm not sure how one would go about making a box whose walls would only block 2.5 gHz.
It just gives me the creeps to know my Microwave oven can't keep a 915 mHz
pager (with a very tiny receive antenna) from hearing a weak signal, from a paging transmitter miles away.

My radio only goes up to 2.0 gHz, otherwise I would be check the leakage of my oven..
When I warm food up, I start it up and leave the room. Wait for the ding.
Strong microwaves or UHF can mess up your eyesight.. Heats them up.

mike95490

Re: Electromagnetic Pulse

The shield frequency is related to the weave of the mesh or the size of the holes. Some shields are reflective (as in a microwave to send the energy into the contents) and some shielding actually absorbs the signals (carbon loaded foam)

An example would be the braid on coax cable, you can get different braid coverages, which allow varied leakage, which changes over frequency.

BB.

Re: Electromagnetic Pulse

More than likely, it is the door "seal" that is letting energy through... It is designed to trap 2.5 GHz energy (and a material that converts leaked energy into heat). 900 MHz is >2.5x the wave length and probably does not even "fit" into the wave trap.

The microwave (screen room/chamber) is not 100% radio wave proof--But only able to reduce radio wave amplitude... The microwave might be able to reduce radio energy by a factor of 1,000x --- But the radio receiver / transmitter may be able to work just fine even if its signal is reduced by 1,000 (30 db)... Remember that cell phones will increase their transmitter power when needed.

From what I can quickly find, a cell phone can receive from +23dbm down to -104dbm or better... That is a 5,000,000,000:1 range (yea, 5 Billion to 1)... If have my numbers correct.

If the microwave/Faraday cage is reasonably close to the cell phone tower, a 1,000:1 or 10,000:1 reduction in power (-30 to -40 db) is still leaves lots of "headroom" for the cell phone to function very well (127 db range).

Disclaimer--I am not a radio expert or even a HAM. And it has been many years since I have played with any RF--so I may have made some serious errors in my above assumptions. But it is a start.

http://en.wikipedia.org/wiki/DBm
http://www.tmworld.com/article/318792-Cell_phones_go_through_the_ringer.php

-Bill B.

SteveK

Re: Electromagnetic Pulse

Sure James happy to share. That second link is Mil Standard test information. It shows the broad spectrum coverage differences between copper and aluminium foils.

Thickness is important, like an antenna. The higher the cross sectional of the antenna the broader the frequencies of coverage. All else being equal, increasing the cross sectional area of the conductive path, or active element, increases performance at a greater range of frequencies.

I have performed no such real life testing but have studied this intensely. I know microwave ovens are pretty useless but the web has stacked them up front as a real solution. I entertained the thought of using an old dryer, or fridge, bonded properly with phosphor bronze fingers to allow easy build and easy access but ultimately went with mesh. Old appliances should work well if properly bonded.

And whatever is used don't forget the internal insulation as well....

I hope it never needs to be tested but if so I believe I am ready.

russ

Re: Electromagnetic Pulse

SteveK wrote: »

I hope it never needs to be tested but if so I believe I am ready.

Me too - I am fully ready and have not done anything. EMP is the last of my worries - down around hangnails on someone else's hand.

SteveK

Re: Electromagnetic Pulse

Yes the priorities would change based on one's location I would imagine.

oil pan 4

Re: Electromagnetic Pulse

"If the microwave/Faraday cage is reasonably close to the cell phone tower, a 1,000:1 or 10,000:1 reduction in (-30 to -40 db) is still leaves lots of "headroom" for the cell phone to function very well (127 db range)".
You are very correct about the microwave part.
I never did get around to building a faraday cage.
I live real close to a cell tower and I tossed the phone in the microwave and only lost a little bit of signal. It registered as going from 7 bars (full signal) to 5 bars.
I even sent a text message to someone that would respond right away, to make sure it could really send and pickup signals with out any problem.

"Be careful not to let anyone Press the Cook button"..
Sometimes its tempting.

bigcountry

Re: Electromagnetic Pulse

i've been reading threw all the post on EMP.

this is probaly a stupid question but was wondering if a EMP blast would take out all electronics even if they are not plugged in and if so would it also take out those that have to be wound up?

BB.

Re: Electromagnetic Pulse

More or less, it is a question of injecting damaging energy into the electronics. It is the attached/un-/poorly shielded cables that do that injection of energy.

EMP (and lightning, far away EMP, solar flares, etc.) tend to be lower frequencies. So, small gaps in electronic enclosures are usually too small to admit any energy. The small gaps tend to be a problem for static electrical discharge (your down jacket, dry atmosphere, you touching the keyboard/computer enclosure/mouse) that is going to cause the computer to reboot--or possibly fry a digital signal input.

Solar flares are very long radio wave lengths which requires miles (or 10-100's of miles) of "cabling" to become an effective antenna to bring energy into electronics (line transformers, etc.) and cause damage.

So, if you have a "close" EMP blast--Then if you are planning on protecting against it--Put your electronics in a metal box and tightly coil attached cables (or disconnect them). If the cables must be attached, do not coil in a circle but coil in a figure "8" to cancel out coupling of magnetic fields.

More than likely, most of your problems will be related to lightning (statistically speaking). If you design your system to withstand lightning, you probably will survive anything else that does not kill you directly.

The EMP/Solar Flares will, more likely, affect infrastructures measured in miles (utility power, communications). If you are off grid with sufficient food/water/fuel/defensive measures to survive X days/months/years--you probably will.

-Bill

thermax292

Re: Electromagnetic Pulse

BB are you taking any precautions with your generator against an emp? I've built a Faraday cage for my Honda 6500is. They will probably set off the second blast as I'm opening the Faraday cage to check the generator from the first blast. Homer Simpson would say D'oh!

BB.

Re: Electromagnetic Pulse

Does the cardboard box it came in count as a Faraday Cage?

In theory, any electronic device with the external cabling disconnected (or wrapped in figure "8" patterns next to the device) is about all I would worry about.

During testing of computers/networking equipment decade or more ago--ESD was the only tests we worried about and passing FCC Class A or B. All of the other surge/injected noise tests never caused any failures on the products I worked on/developed. The "worst" ESD test (human body model) was a few hundred volts. Higher voltages would create corona discharges first which caused a much slower edge rate on the discharge ("softer spark", less high frequency components).

Computers that were not well shielded (probably would not pass FCC Class A or B would be brought down 50' away. Well shielded computers (i.e., all the covers on, properly attached and shielded cables, per normal installations) would take direct and near hits (to a metal plate) without any problems at all.

Solar Flares (and EMP and lightning to a large degree) are much lower frequency events (Hz and kHz vs the MHz and GHz of ESD). and need long "antennas" to couple any significant energy into the local power lines. More or less the old 1/4 wave antenna coupling rules... If the cable (or slot in the chassis) is shorter than a 1/4 wave length of the frequency(ies) of interest, then those antenna can (usually) be ignored.

More or less, I am planning on camping out with enough electricity to run the fridge/freezer for a week or two--Once they are empty, I have much less need for electricity (canned, dried, etc. food).

One thing I am not really setup for is water... I really want a well, but in the city, a well is a pain to permit and drill ($$$$ worth of pain). Lots of filters, pills, and fuel to boil water (and cook) the food I have on hand. I purchased multi fuel camp stove so I can burn the usually available fuels (gasoline, diesel, etc.).

And LED lights (a couple head lamps too) with a good supply of fresh batteries (lithium and AA alkaline)... They will last 5-10 years and most of these small "flashlights" will go for a week or more on one set of batteries. Also have a couple small, cheap, AM/FM radios that will go days to weeks on a single AAA / AA battery in normal use.

Burning a 1/2 gallon or more fuel per day for lights and a radio/tv just is not that important to me (at this point anyway).

-Bill

XRinger

Re: Electromagnetic Pulse

bigcountry wrote: »

i've been reading threw all the post on EMP.

this is probaly a stupid question but was wondering if a EMP blast would take out all electronics even if they are not plugged in and if so would it also take out those that have to be wound up?

"wound up"??? Are you talking about those hand-operated generator radios?

Yeah, I'm afraid that a powerful EMP blast would take out any kind of stand-alone electronics.

But, remember that distance from the EMP site is very important.
http://en.wikipedia.org/wiki/Inverse-square_law
If you are a good distance away from the source of the radiation,
and it emits an omnidirectional pattern, it might not be super strong.
So, some of your electronics (pacemakers etc) might survive.

Maybe only the stuff with antennas will perish..


I once lost an L-band LNA (1296 MHz), that I had installed on a 10.5 foot dish.
It had a well matched helix feed,
and could hear the return of 1296 signals bouncing off the moon (Ham EME).

It could hear the hydrogen line signals from the galactic core (1420.406 MHz).
Just like this..

It was one sweet LNA..

The dish was pointed south and up at about 45 degrees.
A very big bolt of lightning hit about a mile south of us one summer afternoon.
the next day, I tested the system and found my $140 LNA was useless..
It was fried by the EMP.

techntrek

Re: Electromagnetic Pulse

XRinger wrote: »

The dish was pointed south and up at about 45 degrees. A very big bolt of lightning hit about a mile south of us one summer afternoon. the next day, I tested the system and found my $140 LNA was useless.. It was fried by the EMP.

With the lightning that close the failure could have been due to a secondary streamer or even just static discharge.

XRinger

Re: Electromagnetic Pulse

techntrek wrote: »

With the lightning that close the failure could have been due to a secondary streamer or even just static discharge.

I actually saw it coming down, it was pretty fat and 5 seconds later, the noise shook the house.
I didn't seen any streamers, not much zig-zag. It was kinda like a meteor coming down.
When I realized it was due south, I wondered about the health of the LNA.

The system was pretty well protected from lighting, and had survived
many lightning storms before that. Plus many hits that were closer than 1 mile.

It was a PHEMT from Down East Microwave, I think it was like this one:
1420ULNA PHEMT, <0.4dBNF >16dBG, 1420 MHz. RX only! Weatherproof and type “N” connectors. 140.00
But, it had a 0.35 dN noise figure. (I checked it at work).

The 3 turn Helix feed was not a narrow band feed. It had a very good return loss
from about 1270 up to 1570 mHz. (It was version 5 or 6, I lost count)!
The rig was so sensitive, that I could hear noise floor come up, whenever
I pointed the dish so high that it pointed at a overhanging twig with a little bunch of leaves.
GPS sats would overload my radio!


Heck, that LNA might have died of old age, but I'm blaming EMP.