[Dave_C]

I think we all understand that although the probability of an EMP attack is very low, it does rise above zero as tensions with North Korea escalate. I think we also understand that the probability of long-term, post-EMP survival is very low. In light of some of these things and in spite of others, some of us are doing our best to prepare for EMP, and have purchased or are planning to purchase Faraday bags to protect our electronic power, light and communication gear.

For those of you who, like me, are attempting to prep for EMP, the following might be of interest:

I'm developing a bag that:
1) provides upwards of 80 dB of attenuation
2) is as tough and abrasion-resistant as any gear bag you might own
3) is offered in a waterproof version
4) can be custom built to fit your gear
5) will be priced reasonably

Dr. Arthur T. Bradley, a NASA engineer and expert in EMP research, recommends a minimum of 50 dB of shielding for EMP protection (and he demonstrates on his YouTube channel that many items marketed as Faraday bags fall short of this minimum). At 80+ dB, my bags far exceed this recommended minimum, offering a level of shielding that will reduce the electrical field strength of an EMP attack (around 50 kV/m) to the field strength that we experience outdoors every day (about 5 V/m). My bags also exceed the highest attenuation offered by any other commercially available bag that I've seen by at least 10 dB. My bags, unlike high-end anti-static bags I've worked with, are intended for rugged, outdoor use in harsh conditions, and allow easy access to contents and easy resealing without the need for conductive tape. I haven't seen any other company offer custom sizing of Faraday bags. In short, I believe I'm developing the best Faraday bag available.

As I consider moving forward with production, I would like to know if you are interested in a product like this.

 

[bunkerbuster]

I use these, hard to beat for less than a buck each (bought in a bulk 125 pack)

https://www.ebay.com/itm/125-RETORT...042614?hash=item51abb3ddb6:g:CzgAAMXQkl9RbIDS

 

[Dave_C]

I use these, hard to beat for less than a buck each (bought in a bulk 125 pack)

Yeah, that price is hard to beat. What is their shielding effectiveness?

When I first looked into shielding bags, I bought aluminized MIL-PRF-81705D anti-static bags that had an average attenuation of around 47 dB from 100 kHz to 1 GHz. They were all one size, which made them too large for some of my electronics and too small for others. Also, they had to be sealed with conductive tape. I found that they would probably work for storing equipment on a shelf, but they weren't rugged enough to withstand being repeatedly stuffed into and removed from my backpack and being repeatedly opened and resealed.

 

[Jerry D Young]

1) Which dB scale is the 80 dB?

2) What is the frequency range of the attenuation?

3) What is the attenuation for the different frequency bands?

4) Is there internal isolation from the attenuating conductive material?

5) If it does not reveal proprietary information, how are the bags closed to produce a complete broad frequency attenuating seal?

6) Is the outside of the bags conductive or is the attenuating material layered between external insulating layer and inside insulating layer? (Basically, can the bags touch each other in a storage container without problems?)

7) Do the bags meet Mil-Std 461 (RS-105), or Mil-Std-2169?

8) How do the bags compare to the Mobile Sec Solutions bags?

I am quite interested in the bags. I currently use Mobile Sec Solutions bags, (and like them very much) but would like to find an alternative, simply to provide options as I really dislike single source anything.

Just my opinion.

 

[country_boy]

1) Which dB scale is the 80 dB?

Just FYI, dB is a power ratio and doesn't have it units. Often levels are measured in dB from a reference level, which adds an extra unit after dB. But for attenuation ( sound suppressor, ear muff, or electromagnetic shielding) dB doesn't have units.

80 dB would be 1/100,000,000 the power, or 1/10,000 the voltage.

 

[TOO TALL TEX]

Yeah, that price is hard to beat. What is their shielding effectiveness?



When I first looked into shielding bags, I bought aluminized MIL-PRF-81705D anti-static bags that had an average attenuation of around 47 dB from 100 kHz to 1 GHz. They were all one size, which made them too large for some of my electronics and too small for others. Also, they had to be sealed with conductive tape. I found that they would probably work for storing equipment on a shelf, but they weren't rugged enough to withstand being repeatedly stuffed into and removed from my backpack and being repeatedly opened and resealed.

I have some MIL-PRF-81705E bags and was wondering how well they would do protecting electronics. I work at an Airforce aeronautics plant where I pick some occasionally out of the trash.
The only way I know to seal these is to seal the end with aluminum hvac tape. Will this work?


Sent from my iPhone using Tapatalk

 

[Dave_C]

Jerry,

Thanks for your interest. See my comments below.

1) Which dB scale is the 80 dB?

There is only one dB scale that I'm aware of. In this case, it represents attenuation, and is the ratio of the electrical field strength outside and inside the bag.

2) What is the frequency range of the attenuation?

For now, all I have is the attenuation at 2.4 GHz. I'm working on getting the bag tested at various frequencies over the range of 1 MHz to 1 GHz. I will post as soon as this is done.

3) What is the attenuation for the different frequency bands?

See my answer to #2.

4) Is there internal isolation from the attenuating conductive material?

Yes.

5) If it does not reveal proprietary information, how are the bags closed to produce a complete broad frequency attenuating seal?

I'd rather hold off on answering this until I actually start selling the bags. I can tell you that the seal is better than most bags I've seen, which probably contributes to the good attenuation I've gotten. If it turns out that the market isn't big enough to justify manufacturing, I'll gladly share all of the details here for DIY.

6) Is the outside of the bags conductive or is the attenuating material layered between external insulating layer and inside insulating layer? (Basically, can the bags touch each other in a storage container without problems?)

The outside layer of the bag is non-conductive, so multiple bags can safely be stored together. My plan is to offer a waterproof outer shell.

7) Do the bags meet Mil-Std 461 (RS-105), or Mil-Std-2169?

I don't have the required test equipment, and getting certified is way out of my budget for the foreseeable future. I've been in touch with the testing facility at White Sands Missile Range, but I haven't received a quote. I suspect they are no less expensive than other testing companies I've contacted.

8) How do the bags compare to the Mobile Sec Solutions bags?

First, I see that their bags are advertised as RS-105 compliant, which mine will not be unless initial business justifies the cash outlay for testing or purchase of test equipment. Secondly, they advertise that electronics equipment can be used while inside their bags. My bags are optimized for storage and transporting in rugged conditions, not for use of the contained equipment.

I noticed one piece of information on the Mobile Sec Solutions website with which I disagree: "off devices don’t need protection." My understanding is that powered-down equipment is less susceptible to EMP, but only during the E2 phase. That's because the low frequencies of the E2 phase couple into large structures like power lines, not into small electronics. So yes, if your equipment is powered-off and unplugged, it needs no protection during the E2 phase. However, during the E1 phase (1 MHz to 1 GHz), the electrical field couples into integrated circuits to produce damaging currents even in devices that are powered down. (E1 and E2 happen within a few milliseconds.) I've read that some devices might survive E1 undamaged, but it will be hit-or-miss. So, my approach is to protect all of my electronics.

Again, I would suggest checking out Arthur T. Bradley's thoughts on EMP. He's my primary source of technical information.

I am quite interested in the bags. I currently use Mobile Sec Solutions bags, (and like them very much) but would like to find an alternative, simply to provide options as I really dislike single source anything.

Just my opinion.

Again, thanks for your interest. I'm happy to answer any other questions, and will research if I don't know the answer.

 

[Dave_C]

I have some MIL-PRF-81705E bags and was wondering how well they would do protecting electronics. I work at an Airforce aeronautics plant where I pick some occasionally out of the trash.
The only way I know to seal these is to seal the end with aluminum hvac tape. Will this work?

Yeah, that's how I used them. Close the bag by folding the opening multiple times and seal with tape. Arthur Bradley recommends a minimum of 50 dB of attenuation, so it's probably best to double- or triple-bag.

Again, plastic bags like this work for storing away small items on a shelf, but not for transporting larger items and not for repeated reuse.

 

[Dave_C]

I'm posting this for the sake of transparency and to give all who are interested a way to test your bags:

I found a way to measure the attenuation of an electromagnetic shielding bag at a single frequency without expensive equipment. I use a free Android app called WiFiAnalyzer (open source) by VREM Software Development, which is available in the Google Play Store. To test, first disconnect your Android device from your WiFi network (but don't turn off WiFi on your device). Then launch WiFiAnalyzer. If there are a number of WiFi networks available at your location, it helps to filter the list to include only the SSID of the network with the strongest signal (to do this, click on the icon to the left of the pause/resume button at the top of the window). Select WiFiAnalyzer's Time Graph function, and allow it to run for about 30 seconds before putting your device in a bag. This will give you the baseline reading of the signal strength of your chosen WiFi network. Next, with Time Graph still running, quickly put your device into a Faraday bag and seal it. If the inner layer of your bag is conductive, put your device in a non-conductive bag before putting it into your Faraday bag. Otherwise, when the conductive layer touches the device screen, it will cause many touch events to be registered on your device, and Time Graph might be disrupted. After about 30 seconds, remove the device from the Faraday bag. The difference in dB between the baseline reading (the top of the curve) and the shielded reading (the bottom of the curve) gives you the shielding effectiveness of your bag in dB. You might have to approximate the readings, because the scale is in increments of 10 dB. This isn't hard to do. This test will give you the shielding effectiveness of your bag at 2.4 GHz, which is actually outside of the range of EMP frequencies. But it is the best possible indicator of how your bag will perform at 1 GHz short of investing in thousands of dollars of equipment. Supporting this is the fact that in one of their EMP preparedness documents, DHS recommends checking cell phone signal (around 2 GHz, I think) as a way of testing EMP shielding effectiveness.

When I placed my device in my bag, the graph completely bottomed out, so the best I can do is estimate attenuation at around 80+ db. Again, after an engineer has tested my bag at actual EMP frequencies, I'll post the results.

Jerry D Young and bunkerbuster, I'd be very interested to know how your bags perform according to this test.

 

[TOO TALL TEX]

Again, I would suggest checking out Arthur T. Bradley's thoughts on EMP. He's my primary source of technical information.

I’ve watched Dr Arthur Bradley’s video’s, they are very informative.
I’m thinking of using the bags along with putting the bags in a galvanized can and sealed up with hvac tape. That should be well protected.



Sent from my iPhone using Tapatalk

 

[Jerry D Young]

Just FYI, dB is a power ratio and doesn't have it units. Often levels are measured in dB from a reference level, which adds an extra unit after dB. But for attenuation ( sound suppressor, ear muff, or electromagnetic shielding) dB doesn't have units.

80 dB would be 1/100,000,000 the power, or 1/10,000 the voltage.

I do understand this. However, not everyone does. Trying to use a scale that does not apply can give very misleading results. Looks like Dave_C does understand, and I imagine that he is using the dBm scale. But I simply wanted to know for sure.

Jerry,

Thanks for your interest. See my comments below.



There is only one dB scale that I'm aware of. In this case, it represents attenuation, and is the ratio of the electrical field strength outside and inside the bag.
There are multiple scales, but only a very few apply to electrical power and/or radio frequency attenuation.


For now, all I have is the attenuation at 2.4 GHz. I'm working on getting the bag tested at various frequencies over the range of 1 MHz to 1 GHz. I will post as soon as this is done.



See my answer to #2.



Yes.



I'd rather hold off on answering this until I actually start selling the bags. I can tell you that the seal is better than most bags I've seen, which probably contributes to the good attenuation I've gotten. If it turns out that the market isn't big enough to justify manufacturing, I'll gladly share all of the details here for DIY.



The outside layer of the bag is non-conductive, so multiple bags can safely be stored together. My plan is to offer a waterproof outer shell.



I don't have the required test equipment, and getting certified is way out of my budget for the foreseeable future. I've been in touch with the testing facility at White Sands Missile Range, but I haven't received a quote. I suspect they are no less expensive than other testing companies I've contacted.



First, I see that their bags are advertised as RS-105 compliant, which mine will not be unless initial business justifies the cash outlay for testing or purchase of test equipment. Secondly, they advertise that electronics equipment can be used while inside their bags. My bags are optimized for storage and transporting in rugged conditions, not for use of the contained equipment.

I noticed one piece of information on the Mobile Sec Solutions website with which I disagree: "off devices don’t need protection."
I am not finding that quote. I may just not be seeing it (which is a possibility), or I am not looking for it in the correct place. Would you mind linking to it? Thanks.

My understanding is that powered-down equipment is less susceptible to EMP, but only during the E2 phase. That's because the low frequencies of the E2 phase couple into large structures like power lines, not into small electronics. So yes, if your equipment is powered-off and unplugged, it needs no protection during the E2 phase. However, during the E1 phase (1 MHz to 1 GHz), the electrical field couples into integrated circuits to produce damaging currents even in devices that are powered down. (E1 and E2 happen within a few milliseconds.) I've read that some devices might survive E1 undamaged, but it will be hit-or-miss. So, my approach is to protect all of my electronics.

Again, I would suggest checking out Arthur T. Bradley's thoughts on EMP. He's my primary source of technical information.



Again, thanks for your interest. I'm happy to answer any other questions, and will research if I don't know the answer.

I'm posting this for the sake of transparency and to give all who are interested a way to test your bags:

I found a way to measure the attenuation of an electromagnetic shielding bag at a single frequency without expensive equipment. I use a free Android app called WiFiAnalyzer (open source) by VREM Software Development, which is available in the Google Play Store. To test, first disconnect your Android device from your WiFi network (but don't turn off WiFi on your device). Then launch WiFiAnalyzer. If there are a number of WiFi networks available at your location, it helps to filter the list to include only the SSID of the network with the strongest signal (to do this, click on the icon to the left of the pause/resume button at the top of the window). Select WiFiAnalyzer's Time Graph function, and allow it to run for about 30 seconds before putting your device in a bag. This will give you the baseline reading of the signal strength of your chosen WiFi network. Next, with Time Graph still running, quickly put your device into a Faraday bag and seal it. If the inner layer of your bag is conductive, put your device in a non-conductive bag before putting it into your Faraday bag. Otherwise, when the conductive layer touches the device screen, it will cause many touch events to be registered on your device, and Time Graph might be disrupted. After about 30 seconds, remove the device from the Faraday bag. The difference in dB between the baseline reading (the top of the curve) and the shielded reading (the bottom of the curve) gives you the shielding effectiveness of your bag in dB. You might have to approximate the readings, because the scale is in increments of 10 dB. This isn't hard to do. This test will give you the shielding effectiveness of your bag at 2.4 GHz, which is actually outside of the range of EMP frequencies. But it is the best possible indicator of how your bag will perform at 1 GHz short of investing in thousands of dollars of equipment. Supporting this is the fact that in one of their EMP preparedness documents, DHS recommends checking cell phone signal (around 2 GHz, I think) as a way of testing EMP shielding effectiveness.

When I placed my device in my bag, the graph completely bottomed out, so the best I can do is estimate attenuation at around 80+ db. Again, after an engineer has tested my bag at actual EMP frequencies, I'll post the results.

Jerry D Young and bunkerbuster, I'd be very interested to know how your bags perform according to this test.

As soon as I can I will try that test. I already have the app on my phone. I just will need to unpack the appropriate bag to use.

I look forward to the information as you release it. Thanks.

Just my opinion.

 

[Dave_C]

I’ve watched Dr Arthur Bradley’s video’s, they are very informative.
I’m thinking of using the bags along with putting the bags in a galvanized can and sealed up with hvac tape. That should be well protected.

Yes, if you're following his guidelines, you can't go wrong.

 

[Dave_C]

I noticed one piece of information on the Mobile Sec Solutions website with which I disagree: "off devices don’t need protection."
I am not finding that quote. I may just not be seeing it (which is a possibility), or I am not looking for it in the correct place. Would you mind linking to it? Thanks.

Here it is.

Second bullet point under Product Description:

Protect your devices from EMP even when in use. Other EMP bags (which aren’t RS-105 tested) don’t allow use. If your devices aren’t in use, they’re off, and off devices don’t need protection.

Maybe the wording implies a different meaning than what they intended.

 

[Dave_C]

I’ve watched Dr Arthur Bradley’s video’s, they are very informative.
I’m thinking of using the bags along with putting the bags in a galvanized can and sealed up with hvac tape. That should be well protected.

TOO TALL TEX, I forgot to mention that I've seen others do something that I don't recall seeing Dr. Bradley do, which is to seal some additional areas on the inside of the can with aluminum tape--the seam where the sides of the can meet the bottom, the seams where the handles are attached to the sides and the area where the handle is attached to the lid of the can--basically anywhere there might be a small opening through which EMR can leak.

 

[TOO TALL TEX]

TOO TALL TEX, I forgot to mention that I've seen others do something that I don't recall seeing Dr. Bradley do, which is to seal some additional areas on the inside of the can with aluminum tape--the seam where the sides of the can meet the bottom, the seams where the handles are attached to the sides and the area where the handle is attached to the lid of the can--basically anywhere there might be a small opening through which EMR can leak.

I will do that. Thanks!


Sent from my iPhone using Tapatalk

 

[Jerry D Young]

Here it is.

Second bullet point under Product Description:



Maybe the wording implies a different meaning than what they intended.

Okay. Found it. Thank you.

I am not sure why that is there, because, as you are aware, it is not true. I suspect it was written by a marketing guy that does not know better. Because, it is even remarked that the items would be in protective bags, anyway.

Or, I am wondering if they meant that if you need to use a laptop, but still needed protection from EMP, that their products provide that kind of ability with the protection, too. As opposed, if the device is not on, they do not need that type of ability, just the shielding.

Not really sure. But, I do like the products, and will test mine the way you described to see if the attenuation is as they advertise.

Thanks for the replies.

Just my opinion.

 

[franklin]

I'm posting this for the sake of transparency and to give all who are interested a way to test your bags:

I found a way to measure the attenuation of an electromagnetic shielding bag at a single frequency without expensive equipment. I use a free Android app called WiFiAnalyzer (open source) by VREM Software Development, which is available in the Google Play Store. To test, first disconnect your Android device from your WiFi network (but don't turn off WiFi on your device). Then launch WiFiAnalyzer. If there are a number of WiFi networks available at your location, it helps to filter the list to include only the SSID of the network with the strongest signal (to do this, click on the icon to the left of the pause/resume button at the top of the window). Select WiFiAnalyzer's Time Graph function, and allow it to run for about 30 seconds before putting your device in a bag. This will give you the baseline reading of the signal strength of your chosen WiFi network. Next, with Time Graph still running, quickly put your device into a Faraday bag and seal it. If the inner layer of your bag is conductive, put your device in a non-conductive bag before putting it into your Faraday bag. Otherwise, when the conductive layer touches the device screen, it will cause many touch events to be registered on your device, and Time Graph might be disrupted. After about 30 seconds, remove the device from the Faraday bag. The difference in dB between the baseline reading (the top of the curve) and the shielded reading (the bottom of the curve) gives you the shielding effectiveness of your bag in dB. You might have to approximate the readings, because the scale is in increments of 10 dB. This isn't hard to do. This test will give you the shielding effectiveness of your bag at 2.4 GHz, which is actually outside of the range of EMP frequencies. But it is the best possible indicator of how your bag will perform at 1 GHz short of investing in thousands of dollars of equipment. Supporting this is the fact that in one of their EMP preparedness documents, DHS recommends checking cell phone signal (around 2 GHz, I think) as a way of testing EMP shielding effectiveness.

When I placed my device in my bag, the graph completely bottomed out, so the best I can do is estimate attenuation at around 80+ db. Again, after an engineer has tested my bag at actual EMP frequencies, I'll post the results.

Jerry D Young and bunkerbuster, I'd be very interested to know how your bags perform according to this test.

That's no where near a reliable test method.

 

[Dave_C]

That's no where near a reliable test method.

I certainly respect your opinion and would be willing to learn from it. Why do you think it's not reliable?

Here's why I think my test method is a reliable sanity check:

The next phase of testing will actually be very similar to what I've already done. An engineer will take two readings with a spectrum analyzer and an EMR source at each of several frequencies in the range of 1 MHz to 1 GHz. The first of the two readings at each frequency will be with no shielding, and the second reading will be with the spectrum analyzer inside the bag. In my test, I simply used the equipment that I have on hand to imitate what I've seen an engineer do.

The differences between my test and an engineer's test will be: 1) their equipment will be more accurate; 2) they'll be testing at multiple frequencies, whereas I tested at only one frequency. Regarding accuracy, in my test, the shielded signal dropped off the scale, so I could only estimate at 80+ dB. I don't know how much higher than 80 dB the actual attenuation was.

Although I'll get better results in the next phase of testing, i think it's reasonable to assume that I've already gotten pretty good ballpark figures--enough to let me know I'm on the right track with my design.

Again, this is a step up from a DHS-recommended test method.

When I contract with an engineer, I'll ask them to test my bag at 2.4 GHz, and I'll include that reading when I post the results here.

 

[country_boy]

I certainly respect your opinion and would be willing to learn from it. Why do you think it's not reliable?

It's not reliable to to the lack of a precision measuring device or an understanding of the incident signal.

It's akin to testing bullet proof vests against ninja throwing stars thrown by random persons ( it's not scientific- ie not repeatable without your model of cellphone and wifi router, and it's irrelevant because 2.4 GHz represents an almost non existent threat from NEMP)

If you wanted to text bullet proof vests, you look to the average gun responsible for killing police, perhaps 22LR to 45 ACP. While BB guns and 460 weatherby magnums can cause death, it irrelivent to making decisions about ballistic vests for the average LEO.

With EMP, you want to look at frequencies in the main spectral distribution, perhaps focusing on the higher end more since device that will fit In A bag will couple the energy more readily. 2.4 GHz would only be of marginal interest, as it might accentuate problems with openings, while concealing problems with joints ( capacitive impedance is 1000 times lower at 4.5 GHz than at 4.5 MHZ, right near the point where the power spectral density starts tapering off.)

If we're were looking at HERO protection ( protecting ordinance from radiation, especially radar), 4.5 GHz would be a great choice. Ditto if we wanted to secure cellphones to prevent eavesdropping, or tracking ( or realistically ringing- all our SCIFs have supply of these bags where you are supposed to leave your cellphone)

 

[Dave_C]

Thanks for your input. There's some good info there. My comments below.

It's not reliable to to the lack of a precision measuring device or an understanding of the incident signal.

I think you might be taking my admittedly inaccurate 2.4 GHz sanity check too seriously. While my measuring device in this preliminary test isn't precise, as I've already stated, it's close enough to give me an orders of magnitude reading. It has allowed me to compare different design ideas and let me know that I'm on the right track with this design.

It's akin to testing bullet proof vests against ninja throwing stars thrown by random persons ( it's not scientific- ie not repeatable without your model of cellphone and wifi router, and it's irrelevant because 2.4 GHz represents an almost non existent threat from NEMP)

I agree with you that different devices would probably give you different readings of signal strength with the same WiFi router. But the number we're after isn't signal strength--it's attenuation. My device might see a baseline signal strength of -24 dB and yours might see -26 dB. But if mine measures the shielded signal at -44 dB and yours measures -46 dB, then we've arrived at the same attenuation figure of 20 dB. Also, with the testing that I've done, I'm after ballpark figures, not final figures. And yes, 2.4 GHz is beyond the range of EMP frequencies. But in my case, it's a valid predictor of performance based on the attenuation curve of the material I've used. The manufacturer's spec sheet shows readings up to 10 GHz.

With EMP, you want to look at frequencies in the main spectral distribution, perhaps focusing on the higher end more since device that will fit In A bag will couple the energy more readily. 2.4 GHz would only be of marginal interest, as it might accentuate problems with openings, while concealing problems with joints ( capacitive impedance is 1000 times lower at 4.5 GHz than at 4.5 MHZ, right near the point where the power spectral density starts tapering off.)

Look, I think you might have some valid points here. But should we squabble over frequencies that are outside of the range of EMP frequencies?

If we're were looking at HERO protection ( protecting ordinance from radiation, especially radar), 4.5 GHz would be a great choice. Ditto if we wanted to secure cellphones to prevent eavesdropping, or tracking ( or realistically ringing- all our SCIFs have supply of these bags where you are supposed to leave your cellphone)

I'm not interested in blocking radar or cell phone signal or ultimately even WiFi signal. I'm interested in the frequencies between 1 MHz and 1 GHz, and I'll get that info with the next round of testing.

Thanks for your interest. I'm happy to discuss this further with you.