Hazards - Alfa USB 500mW (alfa users come have a look)

[Archangel-Amael]

If you really believe that 500mW isn't enough to cause damage, then I suggest you take your alfa, stick it in your pants for a couple of hours and see how you feel afterwards. After all, science is about proposing a theory and then proving or disproving the theory.

I don't care to see this in action but the after affects write up would be ok to read maybe.
Of course I have had couple RF burns from military radio's and well it hurts!
There was a time when we didn't have any good reliable test equipment for radio antenna matching units, so the "commo guys" would use light bulbs and place them on the metal contacts and turn on the radio. If the light bulb lit up then the matching unit was ok.

[adonishermall]

500mW = .5W

Let's review how a Microwave oven works. On full power, the oven is emitting MW's 100% of the time, but on let's say half power, the oven is only emitting MW's 50% of the time. The amount of power it's radiating doesn't really change, just the duty cycle.

Now let's translate that into using a 500mW wifi card in close proximity of your testicles or eyes. While it may not instantly feel hot, eventually over time, it will heat up and cause damage. Why the testicles and eyes? Because they have the highest concentration of water than other parts of the body. MW's excite the water molecules and cause them to heat up.

I believe you're also mixing metaphors when you're talking Gamma radiation and MW radiation.

MW's are kind of like poison, it's not the poison that kills, but the dose. If you really believe that 500mW isn't enough to cause damage, then I suggest you take your alfa, stick it in your pants for a couple of hours and see how you feel afterwards. After all, science is about proposing a theory and then proving or disproving the theory.

Smart move to prove a theory.. except I love my balls more. :P Well first I thank your opinion on this. So you do agree that wifi can cause damage huh.. only in the long run. I have to agree with you, and yes the eyes does contain vitrous humor, making it rich in water.

So if you were in my shoes, what would you do to counter this ?

[adonishermall]

I don't know where you got that info, but it's wrong.


You seem to be mixing up your terminology. I think someone needs a quick RF lesson from Thorn.

Thx Barry for the correction. At least we make mistakes for the better.

Do you own an Alfa?

[streaker69]

Smart move to prove a theory.. except I love my balls more. :P Well first I thank your opinion on this. So you do agree that wifi can cause damage huh.. only in the long run. I have to agree with you, and yes the eyes does contain vitrous humor, making it rich in water.

So if you were in my shoes, what would you do to counter this ?

Umm, wrap your balls in a faraday cage?

[Barry]

Thx Barry for the correction. At least we make mistakes for the better.

Do you own an Alfa?

Nope, don't need it. My laptop has a supported card (eeePc 701) and my portable computer has at the moment 2 WLM54G 200mW mini pci cards in it. I usually has four of them but I'm letting someone borrow two for a project he's working on.

[imported_di2co]

500mW = .5W

Let's review how a Microwave oven works. On full power, the oven is emitting MW's 100% of the time, but on let's say half power, the oven is only emitting MW's 50% of the time. The amount of power it's radiating doesn't really change, just the duty cycle.

Now let's translate that into using a 500mW wifi card in close proximity of your testicles or eyes. While it may not instantly feel hot, eventually over time, it will heat up and cause damage. Why the testicles and eyes? Because they have the highest concentration of water than other parts of the body. MW's excite the water molecules and cause them to heat up.

I believe you're also mixing metaphors when you're talking Gamma radiation and MW radiation.

MW's are kind of like poison, it's not the poison that kills, but the dose. If you really believe that 500mW isn't enough to cause damage, then I suggest you take your alfa, stick it in your pants for a couple of hours and see how you feel afterwards. After all, science is about proposing a theory and then proving or disproving the theory.

What seems to be missing here is any mention of power density. Yes 500mW gamma can cause serious harm but it has less to do with total power and more to do with power density / focal energy (.5W/10^-9 cm^2 is going to be a lot more harmful than .5W/10 cm^2).

As advanced as a usb dongle antenna is I'm willing to bet it's radiating pattern is less than ideal. To be honest though I have never performed a characterization on one. I don't even know their polarization but I would think they would be constructed to radiate as evenly as possible and even send a good portion of power out the top just to accomodate those that don't know what polarization is and how it effects power relative to position.

Microwaves do not heat water by exciting the molecules. The molecules are achieving higher levels of excitation because they are getting hot not the other way around. I believe the word you were looking for was attenuation. If you "pump" any form of EMR (RF, MW, Xray, Gamma) through any medium there will be some amount of attenuation derived from that medium's coefficient of attenuation for that wavelength. That is the energy coming out of the other side will be less than what went in, it didn't disappear it was "absorbed" by the medium through various means of attenuation.

The "time/distance/shielding" philosophy applies to any exposure to EMR.

To the OP, it's not going to kill you but as a general rule you would like to minimize the time you spend in close proximity to a transmitting device. You will probably die from chewing on the dongle before the radiation kills you. I wouldn't recommend putting your dongle down your pants you're going to get horrible signal quality with it down there (multi-pathing and all). My wife thinks I spend too much time at work as it is.. If I started shoving IT gadgets down my pants I'm sure it would be over.

Correct me if I'm off. The RF nazis will probably hunt me down for my over-simplistic explaination of attenuation.

v/r
Di2co

[Archangel-Amael]

Microwaves do not heat water by exciting the molecules. The molecules are achieving higher levels of excitation because they are getting hot not the other way around.

I am not quite sure what you mean above but;
Bill Nye the Science guy, Professor Lee at the Colorado Univ., The How Stuff
Works website, the International Assoc. for the Properties of Water and Steam and many others disagree with your wording above.
Let's break this down.
Water is made of molecules, molecules can move or be moved.
This movement is called excitation. This excitation causes friction, which produces heat. Microwaves produce excitation in molecules thus producing friction which produces heat. The more excited, the more friction, the more heat. All of this is relevant of course since there are limits. See also supreheated, or boiling retardation. I am not sure I can make it any clearer than that. As for RF burns the same basic thing takes place. Molecules are excited thus producing friction, which in turn produces heat. Take the heat source away the molecules stop moving as fast and produce less heat.
Check out the web for the Army's microwave weapon. I seen this thing in testing and believe me it excites molecules in people!

Correct me if I'm off. The RF nazis will probably hunt me down for my over-simplistic explaination of attenuation.
v/r
Di2co

As for attenuation I will leave that for someone else.

[adonishermall]

Alot of explanation about attenuation.... Yet probably there's no actual way to tell whether alfa causes damage to the human body or not..

We should run some experiments. Any idea how? No sticking up in the pants though..

[Archangel-Amael]

Alot of explanation about attenuation.... Yet probably there's no actual way to tell whether alfa causes damage to the human body or not..

Actually the cards operate in the same frequencies as other devices, and those devices have been proven to cause harm.
As for your experiments please let us know how you get on.

[imported_di2co]

I am not quite sure what you mean above but;
Let's break this down.
Water is made of molecules, molecules can move or be moved.
This movement is called excitation. This excitation causes friction, which produces heat. Microwaves produce excitation in molecules thus producing friction which produces heat. The more excited, the more friction, the more heat. All of this is relevant of course since there are limits. See also or boiling retardation. I am not sure I can make it any clearer than that. As for RF burns the same basic thing takes place. Molecules are excited thus producing friction, which in turn produces heat. Take the heat source away the molecules stop moving as fast and produce less heat.
Check out the web for the Army's microwave weapon. I seen this thing in testing and believe me it excites molecules in people!




As for attenuation I will leave that for someone else.

Yes, you're correct. By excitation I was referring to the literal definition which describes an atom and/or molecule that has attained a higher energy state above it's arbitrary baseline or ground state, thermal energy being a by-product of decay. I was attempting to make a distinction between motion (which is an excited state as it has more energy than at rest) and thermal which is a result of the motion's decay (friction). I was attempting to "paint" a time vs. power picture while describing dielectric heating resulting from dipole rotation but after reading my post again it was in fact a colossal failure. I should have simply stated excitation occurs because of the elevated energy state induced by dipole rotation and is not limited to medium containing water. Excitation does not always result in thermal energy release, it can result in re-radiation as scattering. With respect to the human body absorption of microwaves results in the deposit of that energy heating the tissue.

In my feeble attempt at a simplistic explaination I did get caught in some circular reasoning. My intent was to signify the coefficient of attenuation (absorption being of primary concern) as the primary factor involved when determining what energy a particular wavelength would impart on a given medium (when not talking about ionizing radiation which induce additional effects that require consideration). Although it's water content would have a significant impact on attenuation through absorption it is not the sole consideration. The dielectric heating effect is proportional to the amount of energy attenuated through absorption, specific absorption rate being a measure exclusive to the human body.

If the OP is really that concerned he/she could do some research on that particular wavelength's SAR. You can find permissible exposure limits instituted by various institutions and then make the decision for yourself. Given enough exposure or power any EMF/EMR can cause damage although you may die of old age while waiting for that third eye.

end backpedal

I'm familiar with microwave research for the defense industry. TRW (now NGST) experimented with microwaves before moving to mixed gas lasers as a means for missle defense (google "mthel" or "abl"). If I remember correctly a portion of the microwave equipment was actually donated to a junior college. Would make for some fun labs !

v/r
di2co