Anything that has holes, will let more of some frequencies of EMF through

One place I worked had a room lined with wire netting to keep out interference while testing radio equipment. One day I went to visit the guy who was doing the testing and he was listening to an FM radio. So much for the screened room.

 

I'd like to know , what is the EMF blocking hat you have ,
Amazon and Ebay sell them. They claim to have silver woven into them.
I have a EMF hat that was a gift and wanted to start wearing it more. I also have a small am radio so I thought it would be a good real world test, just to place the radio in the hat and fold it over so it was completely enclosed.

So the trouble you will have with the AM radio is the wavelength of the signal. Longer wavelengths (lower frequencies) are much harder to reflect (which is the mode your hat tries to use).

To keep RF away from something you can either absorb the signal (turn to heat or redirect to ground) or you can select it. When the wavelength gets to be below something of the order of tens of MHz, EM blocking textiles don't work.

As the frequency rises, the attenuation increases. The higher the frequency the more the attenuation. This assumes the textile the hat is made from is an effective attenuator but even if it is of decent quality it may have a very limited effective bandwidth.

EM blocking textiles were created to improve shielding of electronic enclosures, not for clothing, so the effectiveness as clothing will not be as good that the ratings of the manufacturer which include good application (electrical connection) and grounding.

I really don't know if there is a meaningful attenuation in garments. I do know that in enclosures the textiles can make a large difference in handling the gaps (e.g.: on doors and other access ports) that would otherwise interfere with shielding. Normally, it is intended to keep radiation in not out but I can't see how that would make a difference in the amount of isolation you can achieve.

 

Wrong. Radio and cellphones have nothing to do with photons. Did you learn physics from a correspondence course? You've been seriously misled. Any opaque object will block photons.

Could you define "opaque" please?

 

EMI shielding (reflecting) gets more and more difficult as the wavelength gets longer.

Alternatively, you can ABSORB the EMI and invert it to heat. Certain molecular bonds absorb at specific wavelengths in the mid-infrared wavelengths (a given bond will have vibration resonances at a narrow to relatively broad frequency range within the mid-IR (microwave) 7μm - 14μm wavelength range - and at corresponding overtones).
For broad-range attenuation via EMI absorption, using a magnetizable material (iron, ferrites, nickel, permalloy, ...) can work well. In general, the less electrically conductive, the better - there is no single material that can absorb across the entire spectrum. On top of material selection is material processing technology - methods to render a conductive material non-conductive beyond a very (VERY) short distance if using magnetic, metallic alloys or elements.

 

One place I worked had a room lined with wire netting to keep out interference while testing radio equipment. One day I went to visit the guy who was doing the testing and he was listening to an FM radio. So much for the screened room.

All RF shielding has an effective frequency. For proper TEMPEST shielding we usually had several shielding types with overlapping ranges for both the magnetic and electric components of the target.
https://www.comtest.us/solutions/rf-shielded-enclosures/tempest-shielded-facilities/
https://www.nsa.gov/portals/75/docu...ed-documents/cryptologic-spectrum/tempest.pdf

 

All RF shielding has an effective frequency. For proper TEMPEST shielding we usually had several shielding types with overlapping ranges for both the magnetic and electric components of the target.
https://www.comtest.us/solutions/rf-shielded-enclosures/tempest-shielded-facilities/
https://www.nsa.gov/portals/75/docu...ed-documents/cryptologic-spectrum/tempest.pdf

I bet it was dark in there as well
May be they wanted to keep the photons out :->

 

I bet it was dark in there as well
May be they wanted to keep the photons out :->

There was plenty of power inside the crypto-technical control facility to generate our own photons.

 

What if I were to tell you that we human beings emit light?
It is Non-Ionizing Radiation (NIR) waves the human body emits naturally and is detectable in the electromagnetic and optical range.
No special equipment is needed to facilitate this bioelectric phenomena.

 

If you have eaten a banana lately, you are probably emitting a tiny amount of ionizing radiation.

 

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006256

 

we human beings emit light?

Certainly all objects emit IR radiation, as determined by their temperature.
IR from a human peaks at about a 10 micron wavelength.
That's how a FLIR camera generates an image in the when it's (visually) dark.

 

If you have eaten a banana lately, you are probably emitting a tiny amount of ionizing radiation.

Or brazil nuts.

 

Certainly all objects emit IR radiation, as determined by their temperature.
IR from a human peaks at about a 10 micron wavelength.
That's how a FLIR camera generates an image in the when it's (visually) dark.

BUT

Would the hat in the question stop this ?
:->

 

Through Color coronal spectral analysis spontaneous biophoton emissions spanned the entire visible electromagnetic spectrum as well as Thermo, infrared spectrum.
When we eat a banana the process of metabolism changes our cell membranes creating electric dipoles both polarized and ionized molecules are created due to cell metabolism these molecules are continually destroyed and restored in the process emitting electromagnetic radiation.
Fray A.H. (1997) Electromagnetic fields interaction with biological systems
FASB journal
Chiang L.H (2005) Bioenergy based medical diagnostic based on gas discharge visualization. IEEE.Eng.Conf.Med.Biol.Soc.,2:1533
@AlbertHall you got me on Brazil nuts.