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horsevad
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# Posted: 24 Nov 2016 22:57 - Edited by: horsevad
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Shielding FAQ:



Prerequisites:
Before any shielding projects is undertaken it is vitally important to acquire the means to make actual measurements of the exposure - and exposure reduction.

A measurement device capable of measuring down to the safe exposure ranges published by the german building biologists is recommended.

There is a tabular overview of the relevant values here:
http://rf-emf.org/Publications/SBM2015---Tabular_Presentation.pdf


Electromagnetic fields:
Electromagnetic fields is formed from a combination of electric and magnetic fields.

In the far field region (more than two wavelengths from the antenna) the to fields are combined to make the electromagnetic field. If one part is removed (eg a Farady cage shielding the electrical field) the other field collapses and the whole electromagnetic field is removed.

In the near field region (less than one wavelenght form the antenna) the two component fields (electrical and magnetic) can exist independently of each other. This means that if the electrical field is shielded by a Farady cage the magnetic field is not affected in the same way as in the far field region.

A Farady cage only shields against electrical fields and the electrical component of the electromagnetic field. A Farady cage has no effect on magnetic fields.

This means that if the Faraday cage is in the near field of the antenna the magnetic field will penetrate the Faraday cage.


Calculations:
Wavelength and frequency are related by a simple formula:

= c/f

Where:
is wavelength measured in meters
c is Speed of light (299792458 m/s)
f is Frequency measured in Hz


An online calculator is available at:
http://rf-emf.org/calculations.html


Complete shielding is necessary:
Partial shielding will only seldom have the desired effect - and can ( in many cases ) actually make the problem worse due to unwanted reflections.

In most cases a full Faraday cage is necessary. This means that both walls and roof should be shielded.

There should be continuous electrical contact between the material shielding the different parts of the structure. Ideally no opening should be larger than 1/40 wavelength.


Shielding of floors:
For best result it is recommended that the floor is shielded too. This will be of great importance in any multi-storey building where there usually are exposure sourced located at a lower level than the floor.

The exact importance of floor shielding can only be calculated fully if one knows the topographical layout of the area in question and has access to soil data. The effectiveness of the shielding is in such cases dependent on the the absorbing characteristics of the soil to attenuate any electromagnetic signal from entering the house from below. If, however, the building to be shielded is situated considerably lower than the antenna mast floor shielding, and there are no exposure sources at a lower level than the house foundation floor shielding can usually be omitted with minimal impact on the total shielding effect.


Windows, doors:
To achieve full protection from the constructed faraday cage it is further necessary to make provisions for shielding windows, doors and other openings. This can be achieved by the means of shielding curtains or special laminates designed to be placed over the window glass

All parts of the enclosure should have electrical contact over the whole surface of any joining. Use a multimeter to verify that the resistance is as low as possible.


Choice of material:

All electrical conducting materials can be used for shielding purposes.

Sheets of corrugated aluminium can be ued for external shielding of roof and walls.

Special electrical conductive paint can be used for internal shielding of roof and walls.

Cheap aluminium netting can be used as a replacement for expensive special products. The samples I have tested has shown attenuation values around 30 - 35 dB, which equals more than 99,9% reduction. This means that other imperfections in the enclosure will be the limiting factor and not the material in itself.

If netting is used the mesh size should be smaller than 1/40 of the wavelenght of the highest frequency one wishes to shield against.


Grounding:

Local electrical code will probably mandate grounding of any electrical conductive building details. This is a safety feature of modern electrical installation, where the RCD should be able to break the power supply before a person is electrocuted if a fault were to develop.

Other reasons to make a proper grounding is the removal of the possibility of RF-energy re-radiating from the shielding material.

Grounding also improve shielding effectivness for low frequency electrical field.

Grounding has no effect on the shielding effectiveness in the microwave frequencies.

The important aspect of grounding is to make sure that the earth rod has sufficient electrical contact with the soil. This resistance can be measured in many ways (depending on the exact layout of the electrical infrastructure), but is really important. The lower value the better.


Faraday cages and quality of grounding:
Some people have reported feelings of discomfort while staying in a Faraday cage, which usually is the result of electrical disturbances from other installations entering the Faraday cage though the grounding connection.

In some instances the level of leak currents from nearby SMPS or similar thyristor-based equipment can make the farady cage radiate RF along any discontinuities in the structure having an impedance allowing a resonance between the structure and any overharmonic component in the leaked current. The electrical component of this field is shielded by the Faraday cage, but the magnetic field can fully penetrate the Faraday cage. Only a very good ground connection (low ground resistance - ideally better than 5 Ohms) can mitigate such scenarios.

Furthermore there may be layers in the soil which are conductive and electrified by some installation fault several miles away. Such scenarios are extremely rare, but can result in situations where the Faraday cage itself is electrified.

A quantitative measurement of such scenarios can be made with different electrical measurement apparatus, but the simple layman qualitative measurement is made with an AM radio. Tune the radio so that it only receives noise - then bring it closer to a earth rod - or the connected Faraday cage. If the noise intensifies as the radio is brought closer to the earth rod one would be well advised to investigate further.


Schumann frequency and Shielding:
The electrical reflecting properties of the ionised layers of the upper atmosphere creates a resonance chamber for the ELF fields propagated by ligthning. The resonance frequency for this system is 7.83Hz, which is called the Schumann frequency.

Several research projects has determined that the Schumann frequency has a tremendous importance for human health.

This is of primary importance for astronauts and people working in large military underground bunker complex with thick walls of steel.

Any faraday cage constructed within the realms of non-military funding will not, in any measurable way, be able to attenuate the magnetic field of the Schumann frequency.

The wavelenght for 7.83 Hz is 38314 km, which means that everywhere on Earth will be in near-field. This means that even a perfect Faraday cage cannot remove the magnetic component of the Schumann frequency.


//Kim Horsevad

louisbourque
Member
# Posted: 9 Apr 2018 03:00
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Dear and esteemed fellows,

I'm writing to demand a similar opinion than the one you provided very precisely here, on « Schumann frequency and Shielding ».

In doing so, I'd politely ask you to forbid my flawed ESL please.

Our young support organisation, the RESQ, muses on the idea of acquiring a park of campers and home-converted buses to accomodate electrosensitive members. Uncommon although logically attuned to our context (please see below), this rises questions about the effets of living a life shielded in a faraday cage, or a metallic vehicule.

Thus, I would like to benefit from your experimented opinion about the long terms health consequences of such a prolonged shielded life.

For instance, geobiology sheds light upon the importance of electromagnetic fields and emissions occuring naturally. Schumann and sunlight being some of them but others, circulating distinctively on grounded grids or «chimney», are deemed beneficial, or detrimental as well.

I Also remember a report on an American experiment where teacher gathered students underground, in a lead bunker for study. After a month, many were severely depressive, or misphased.

Therefore, I wonder if you'd be able to explain more about which natural electromagnetic phenomena is modified, or shielded by a Faraday cage (a resting vehicule). And by exerting which effect on mental and physical health?

In such shielded setting, could you say if sunlight sufices to maintain health?

And does grounding the vehicule (in the country) exerts an effect upon the condition of exposure to these naturally occuring fields, inside the Faraday cage?

Similarly, polar displacement of alternative or static magnetic field is deemed to effect health over the long term by baubiologists. Would you be concerned in the case of a large chassis-vehicule?

In all the aspects mentioned above, would you consider a vehicule to pose the same concerns a true Faraday cage poses?

...

Another aspect of the question would be chemical. Metallic oxydes inhaled on the long term don't act metabolically the same way. And I often read different metallic elements influences vigor, or biological processes more subtely, by proximity or their «energy», for Bovis and the like.

Therefore, I wonder if you could recommand a singular metal, being steel or aluminum for vehicule, or copper for indoor shielding?

...

Finally, should we think the vehicule's electrical system to exert any detrimental effect when the engine is off? I suppose the vehicule mass, connected to the battery, produces a static field.

...

I truly want to thank you for your reflexion, and possible contribution.

To contextualize if needed, the question of health in shielded environment matters all the more authoritie's denial punishes in Québec. On the one hand, ressources are scarce. On the other hand, State denial makes «white zones» a precarious attempt for settling if any, because Utilities are endowed expropriation powers whereas municipalities can localize, but not forbid the installation of a transmitter. Judiciary trials over transmitter granted utilitie's rights over public health.

As a consequence, the capacity to move and recompose geographically matters a lot here. As war is the art of movement, said Vauban.

Thanks a lot, with kindest regards.

Louis Bourque

for the « Regroupement électrosensibilité Québec »
https://electrosensibilitequebec.com/

horsevad
Member
# Posted: 30 Apr 2018 18:01
Reply 



(..)
Thus, I would like to benefit from your experimented opinion about the long terms health consequences of such a prolonged shielded life.
(...)



You will not be able to shield the Schumann resonanses. Even a perfect Faraday cage is completely transparent for magnetic fields.


Problems could arise if the shielded structures are near powerlines, Wind energy installations or similar structures, as stray currents from such installations may reach the shielding material - and thereby imposing a foreign field on the outside of the shielding enclosure.

//Kim Horsevad

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