# Frequency Propagation and Attenuation



## RobynC (Jun 10, 2011)

What things can block microwave frequencies in the 100 MHz to 10,000 MHz range?

What things can block the Schumann Resonance frequencies


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## Zombie Devil Duckie (Apr 11, 2012)

(sorry, I had to)

:tongue:



-ZDD


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## Zombie Devil Duckie (Apr 11, 2012)

This video is kind of related... it's an example of a Chlandi plate. 







http://www.physics.ucla.edu/demoweb/demomanual/acoustics/effects_of_sound/chladni_plate.html


http://americanhistory.si.edu/science/chladni.htm



-ZDD


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## countrygirl90 (Oct 11, 2012)

Microwave propagation as I know of could be disrupted or blocked through diffraction or atmospheric factors like moisture ,ionization or fading .


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## RobynC (Jun 10, 2011)

@_Zombie Devil Duckie_



> This video is kind of related... it's an example of a Chlandi plate.


So these shapes are caused by vibrations/reverberations and standing waves? 

Can you explain the mechanism of action better?

BTW: The tin-foil thing is really counterproductive..


@_countrygirl90_



> Microwave propagation as I know of could be disrupted or blocked through diffraction or atmospheric factors like moisture ,ionization or fading.


Which factors work the best and under what conditions?


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## countrygirl90 (Oct 11, 2012)

RobynC said:


> Which factors work the best and under what conditions?


 I think the answer to this is simple, of course the atmospheric factors ,because I have noticed that during monsoons or foggy winters its just very difficult to get a good reception ,even if I'm using a high speed connection but during summers or spring season when weather is clear and there is almost dry and pleasant kind of atmosphere, reception of signals becomes quite good even with normal connection .


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## Zombie Devil Duckie (Apr 11, 2012)

> BTW: The tin-foil thing is really counterproductive..


Jeez, some people just have no sense of humor...

:tongue:


however........ if you are concerned about ELF shielding, you might look here: 

Shielding Tips

and read this .pdf (link opens .pdf automatically) 

http://www.wvminesafety.org/PDFs/Additional%20Information%20Table/Adaptive.pdf



-ZDD


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## RobynC (Jun 10, 2011)

Zombie Devil Duckie said:


> Jeez, some people just have no sense of humor...


Because it takes away any legitimacy from the discussion

As for the link, it's fascinating and I'll get through reading it, but I'm wondering if there's basically some rules of thumb as to what substances absorb what frequencies and so on?


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## Zombie Devil Duckie (Apr 11, 2012)

> Because it takes away any legitimacy from the discussion


So... would that make it an illegitimate discussion?


:kitteh:


Anyway....... as for your question, I'll see what I can dig up. 


-ZDD


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## Zombie Devil Duckie (Apr 11, 2012)

@_RobynC_ I found a website you might like to look though:

RADIO WAVES below 22 kHz


-ZDD


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## RobynC (Jun 10, 2011)

@Zombie Devil Duckie

1.) Thanks for the last post, I'm checking it out
2.) As for frequencies above 100 MHz to 10,000 MHz, those are well above 22 KHz


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## DemonAbyss10 (Oct 28, 2010)

was gonna suggest a faraday cage or something that would generate Ionic interference. Of course generating that sort of interference just really isn't practical.

Of course you can buy a frequency jammer, of course the legality of such is questionable (not to mention getting you put onto watch lists unless it is for research purposes.


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## easyvision (Jun 11, 2012)

DemonAbyss10 said:


> was gonna suggest a faraday cage or something that would generate Ionic interference. Of course generating that sort of interference just really isn't practical.
> 
> Of course you can buy a frequency jammer, of course the legality of such is questionable (not to mention getting you put onto watch lists unless it is for research purposes.


+1 for the faraday cage. some aircraft bases use microwave landing systems, see if you can find an instruction manual haha, you know how your tv manual says on the front pages, don't put near this , don't do this, well you might accidentally find some information.


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## DemonAbyss10 (Oct 28, 2010)

easyvision said:


> +1 for the faraday cage. some aircraft bases use microwave landing systems, see if you can find an instruction manual haha, you know how your tv manual says on the front pages, don't put near this , don't do this, well you might accidentally find some information.


I remember at the one place I lived, The whole place had drop cielings. My stereo uses a wire antenna so I had the idea of weaving it through that metal drop frame. I was then able to pick up non-AM/FM bands, even when I had the radio function switched off. I would pick up truckers, police/EMS/Fire dept, and the local NG armory.


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## Stelmaria (Sep 30, 2011)

Oxygen in the air attenuates Microwave and low frequency radiowaves quite effectively. 
But if you are talking about clothes that might protect from the US ADS, then I'd suggest something like this:
http://www.nf6x.net/wp/wp-content/uploads/2007/05/navships0967-316-3010.pdf


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## FlightsOfFancy (Dec 30, 2012)

A common rule of thumb (even though it belies the intricacies of actual propagation) is the the wavelength need be smaller than the intermolecular distance/size of the atoms in order to go through. However, any wave can penetrate most molecules given sufficient energy; this has more to do with quantum mech (recall, in quantum mech, potential barriers are they are seen in classical mech can be TUNNELED THROUGH. i.e. solid objects can move through one another).

As for attenuation, this can be accomplished by phase changes. A wave 180 degrees out of phase will completely cancel out its cousin, while slight out of phase waves, e.g. 90 degrees out, will lead to about 50% attentuation. Such phenomena is exploited when you hear 'beats'.

This question really deals with more QM theory and is not readily answerable without a grasp of that (in fact it's a question I've posed to a professor of physics because I don't understand it completely).


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## RobynC (Jun 10, 2011)

Flights of Fancy,

I'm not terribly knowledgeable about tunneling or redirecting sonic waves at angles 180 degrees to themselves. I suppose I have some intelligence on some things, but I'm not a physicist

BTW: I should know this in more detail, but how does a faraday cage work?


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## FlightsOfFancy (Dec 30, 2012)

RobynC said:


> Flights of Fancy,
> 
> I'm not terribly knowledgeable about tunneling or redirecting sonic waves at angles 180 degrees to themselves. I suppose I have some intelligence on some things, but I'm not a physicist
> 
> BTW: I should know this in more detail, but how does a faraday cage work?


I'm not a physicist by trade--I just minored in it. Kind of caught the lazeh before I finished and just was not going to do that big ass research lab.

Some of this you know, but probably not in physics language. If you draw a cycling wave, and draw the opposite of it, you can see that if you add together the parts (fancy name--integrate), you see they cancel each other out. This really is only good for waves that aren't particularly dangerous; it's what is used for sound-canceling headphones etc. For gamma rays, etc, I doubt you'd want any phase of those near your body, as phase really doesn't matter (a football to the gut is gonna be a football to the but no matter if it's a counter-clockwise or clockwise throw, for example).

A Faraday cage works by electric diffusion, basically. In an ideal conductor, charges distribute fairly evenly. When a charge is introduced, i.e. electric current (cause by NEGATIVE electrons), the metal basically will distribute the charge. Imagine one side being hit by this, while the other remains largely positive. By the time it gets to the other side (roughly, electricity is a haphazard beast), there is a positive charge created, which nullifies the negative charge. Why does it travel in this path instead of through your body? Electricity is lazy, it likes to go in the path of least resistance like water; it will go in the direction where voltage is greatest. Your body doesn't have more electric potential (as clear of a path) as the metal, so the metal wins.

Cool fact: Planes are often seen as stuck by lighting and falling all the time. This is a rare cause in real life (almost never) because plane designers use insulators between the other metallic portion of the plane in order to exploit this action. Your plane is likely struck by lightning a good 2-5 times during a flight.


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## g_w (Apr 16, 2013)

RobynC said:


> What things can block microwave frequencies in the 100 MHz to 10,000 MHz range?
> 
> What things can block the Schumann Resonance frequencies


A *LARGE* bag of popcorn? :tongue:


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## FlightsOfFancy (Dec 30, 2012)

g_w said:


> A *LARGE* bag of popcorn? :tongue:



genius it probably would work tbh LULZ.


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## RobynC (Jun 10, 2011)

FlightsOfFancy said:


> genius it probably would work tbh LULZ.


Which frequencies would popcorn block out?


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## FlightsOfFancy (Dec 30, 2012)

RobynC said:


> Which frequencies would popcorn block out?


ohh, i don't know specifically, as virtually any substance will absorb at a slightly different frequency, and popcorn itself is not always homogeneous. It was more of a joke, but I'd guess the majority of the microwave spectrum.


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## RobynC (Jun 10, 2011)

How'd polystyrene do?


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## FlightsOfFancy (Dec 30, 2012)

RobynC said:


> How'd polystyrene do?


My first thought to guide you was Beer's law (it's much less savory after the last drop as a good Heineiken). While it's used for UV light; there are apparently some applications which show its applicability to infrared to gamma rays.

Absorbtion is not a beast that's easily answered, however. I rather not mislead.


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## RobynC (Jun 10, 2011)

@FlightsOfFancy

1.) So polystyrene might not be the best choice... regardless it's toxic

2.) Do you think this link
http://www.nf6x.net/wp/wp-content/uploads/2007/05/navships0967-316-3010.pdf
would be useful?

3.) How do you build a faraday cage?


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## FlightsOfFancy (Dec 30, 2012)

RobynC said:


> @_FlightsOfFancy_
> 
> 1.) So polystyrene might not be the best choice... regardless it's toxic
> 
> ...


Remember, I'm more of an applied mathematical scientist; I am not a physicist by trade, so I am going to best advise you on my current knowledge set.

1) No, it would not be.
2) Looks like it. If the ultimate goal is to deflect Microwaves, then anything material that could be mustered to do so would work. Kind of like how you can take kevlar and make it into a bed sheet if you wanted. Ultimately, it's the material here--not its intended use.
3) Faraday cages depend on there being a rich pool of electrons with an insulated barrier in-between (or something with such a rich pool that whatever is inside is not as desirable due to voltage/high resistance etc).

Basically a really good conductor (the enclosure) with a really good insulator (in the enclosure around the materials desired for protection) make a good Faraday cage. This is a very lose manner of looking at it. For exactitude, you'd need to iron out the engineering a bit and consider: the amount of current you intend on shielding from, a material that has low electrical resistance, and a material with high electric resistance and high thermal capacity (active electronic resistance or resistance for any matter causes heat). 

I don't know what you're intending with this? Most microwaves are incidentally great Faraday cages because the manufacturers have to limit the amount of Microwaves that escape the enclosure. If I were trying to do something along these lines, I'd just buy a cheap microwave and keep whatever it is I wanted to resist the microwaves in it (I think Snowden used a freezer? Same idea, the freezer has an insulating barrier to keep everything cold).

Do remember, this is theory. Engineering, especially with electricity, needs finer tuning to be safe(Ohms law calculations for example). I'd not attempt these even with my knowledge base because it's theory. I'd do tons of research on the application, though it is much easier to learn once you understand the principles of 'why'.


Dunno what this is for, but I hope I helped.


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## RobynC (Jun 10, 2011)

@flights of Fancy

1.) I'm not as good at physics as I should be so I'm not 100% sure what Ohms are... it's a function of electrical resistance but I don't know any more.

2.) Regarding the faraday cages: The cage has to be set to the frequency and spacing of the waves right?
That is determined by the velocity and frequency, of which the velocity is around 297,000 kps right?


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