DIY EMI meter for wifi frequencies

[Ig_sherwood]

Hi there guys .
Around the net i didn't find something about : how to make your own emi wifi meter .
For me this RF-EMI meter would be and actually is, an important stuff.
Let me explain a little bit my situation.
I feels my self very bad,tired,confused and distracted when i stay near at wifi adapters like awus036h ,nh,nhr ecc ...
To solve this problem or make it less dangerous for my health ,i had think in the past to buy this meter here :
http://tinyurl.com/jfwtplq

I don't know if this model will be good enough ,to be honest i really don't know nothing about which meter i must to keep to let me know the level of EMI power which actually is winding me around.....
However i will be really glad if you will give me your advices on the possible models to buy at reasonable price.
Please don't forget that : im also interested about the DIY of this kind.

[julianhigginson]

interesting problem to have. I've never met anyone with this kind of condition but seem to hear about it a bit lately.

anyway - as for your product, here's my 5 minute investigation:

specs claim it'll work at 2.45GHz with +/-2dB accuracy... which is probably good enough for your purposes.

though it has a range of 50MHz-3.5GHz - depending on what else is going on in that huge band, and its sensitivity/accuracy at other frequencies in that band (think mobile phone radiation! that's way more powerful than wifi, tends to be roughly below 1GHz depending on where you are and what carrier you are with) so you may get some misleading readings if all you care about is wifi strength... ideally you might want something filtered to 2.45G ISM if wifi is the thing that worries you.

power range of 0.01 to 44.4uw/cm^2 might be not make it as sensitive as you'd like?
this site claims you can see from 0.1V/m up to 6V/m from an Access Point
http://www.wifiinschools.org.uk/16.html
which is 2nw/cm^2 (0.002uW/cm^2) up to 9uw/cm^2
so you won't see lowest power wifi signals, if that's an issue.

No spec on what length of transmission it can reliably intercept.. but I'd expect that for this issue it's overall energy that'd be the problem, not burst energy? that said I don't understand the biology and physics of this problem, so it's impossible to say if that matters or not.

Bottom line - this will probably give you a basic reading you can look at to see what's strong and what's weak. but won't see everything.


Maybe you'd be better off with a phone app that gives you wifi strength out of the phone's mobile radio circuit? I'm not sure if iphone lets this happen or not, but there's plenty of wifi analysis apps that you can get for android for free or close to it.

Otherwise a wifi module and an arduino could probably be made to work as a pretty good wifi-only field strength meter if that's the kind of thing you could build yourself. (just check the module can do RSSi on the different channels while not connected to an access point)

[BobC]

On Android, take a look at the "Wifi Analyzer" app.  It won't do all you ask for, but will show lots of useful information, and it's free.

[raspberrypi]

Please don't get caught up in that smart meter/ wifi radiation conspiracy. If you look closely you will find its confirmation bias and or placebo effect. If wifi bothers you, your micro wave oven is REALLY going to bother you, your cell phone, and all sorts of wireless stuff. Get an SDR to see for yourself, you will find there are MUCH stronger signals then your wifi and if that frequency range was a problem then its not just your wifi. You would have a very high "exposure" level going into hospitals that use the ISM band problems around communication towers and other things. The "sick" feeling seems to go away when you realise its all around you, always has and always will. This reminds me of the Claritan antihistamine potentiates the effects of narcotics because promethazine can do that. Its literally the same thing just replace drugs/anti histamines with RF and you will find that the "effect" is 100% psychological.

This will be the topic of one of dave jones' "Bullshit" videos one day.

Cheapest *funnest) way to see RF is to buy a 20$USD SDR dongle from adafruit.com. Comes with a small antenna that you could plug into a lap top and walk around with it. But like I said once you see what kind of signals are actually out there you are going to think twice about asking if "wifi radiation" is bad for your health since you have been bathed in some form of it for your whole life.

Another resource I would use is just go to wikipedia and learn how EM radiation works. The photon is the force carrying particle and you will find that light/ wifi/ gamma rays/ UV and Xrays are all just different flavours of the same thing. Things do get different when you go from purple light to UV, its a gradual transition but once you get into the UV energy ranges, which is measured in "electron volts" or eV you will find that photons of that wave length have the ability to change the orbit or valance of electrons in atoms. The length of the jump is determined by the eV of the incoming photon. The higher the jump the more energy. This effect can actually generate Xray photons from Kilo electron volt electrons making kilo electron voly photons which are xrays. Works bothforward and backwards. MAny new fusion reactor designs are using this to generate electricity directly from Xrays skipping the step of heating up a fluid. This is called ionization and what makes florescent lights/plasma TV and many other things work You will find that a CFL tube can actually put out harmful radiation that your wifi can't. But most of it is absorbed by the glass tube or phosphorous coating. When an atom is ionized its put into a reactive state able to perform a chemical reaction. This is why UV is bad because it ionizes the atoms in the molecules in your cells allowing the hydrocarbons in them to react with other molecules like oxygen. A sunburn is actually a burn. The concern comes from when a strand of DNA gets ionized and its past the error checking stage in the replication process. That means cancer.

The other threat from non-ionizing EM radiation comes from localized heating of proteins possibly damaging the ones responsible for DNA production. This is from the non-ionizing EM and work by exciting resonances in the bonds between atoms, BUT can not break the bonds by itself.This is how microwaves heat water.

So look up : eV , frequency vs wavelength vs electron volt, microwave heating, okazaki fragment and DNA replication, ionizing radiation. You will actually find that photons are also involved in keeping us from falling to the center of the earth and why we cant walk through walls, same particle as light.

Or get caught up in the EMF scare and threaten to shoot the meter man who tried to install a smart meter, like one fine american did because of pure ignorance.