Free wifi solution.

[stj]

Re: Free wifi solution.

Bollocks. Utter, complete, bollocks. First, you cannot compare a 100mW wifi router to a 300W+ cellphone tower.

decent routers run 400mw+
and safe working distance for a 100mw CLIENT is 1.5m under canadian guidlines.

i have seen routers with multiple 400-500mw chanels in them running in parallel.
stuff like the comercial 2wire routers.

[tom66]

Re: Free wifi solution.

A **hacked** router may run 500mW, but a licenced and correctly operating one is limited to 100mW (20dBm) in the EU which is measurable using a $100 RF power meter, or even with a basic smartphone with modified firmware.

The ERP for a wifi router is 100mW **across ALL antennas**, the received power at the human body 1m away will be less than 1mW due to the inverse square law. surface area of antenna vs surface area of a whole sphere at 1m. basic fucking physics. there's no mystery here and why this still seems to evade you baffles me, as you seem like a smart guy.

For comparison - microwave oven leakage can be up to 1W within 10cm of door handle.

[stj]

Re: Free wifi solution.

A **hacked** router may run 500mW, but a licenced and correctly operating one is limited to 100mW (20dBm) in the EU.

lol
rules ^=real world.
go look at the output of the Ubiquiti routers or the TP-Link WA5110G or WA5210G
there are others that are even higher from the retailer too.

[tom66]

Re: Free wifi solution.

If those are sold in the EU they are illegal and likely to be fined. Perhaps the manufacturer is quoting ERP with antenna gain, which is not a valid conversion. If they're from China direct then I guess anything goes.

But, even 500mW is not harmful. It isn't high enough to cause significant tissue heating, and the power rolls off very quickly. Still under 1mW at 1m.

Microwave radiation doesn't cause cancer directly because the frequency is not high enough to knock electrons free from their energy bands and change the properties of atoms. You need to reach Xrays/gamma rays to do that. The worst it can cause is tissue heating and burns which could cause secondary cancers due to cell damage. But the thing is, although we're mostly water (which absorbs microwaves well) we have a high specific heat capacity which means we can absorb a lot of energy before we burn.

There have been cases of microwave oven interlocks failing, and people absorbing 1kW+ at 2.4GHz. The result is generally severe burns, usually causing skin damage and nerve issues. AFAIK, no one has died from this (I'll try and find a case study) - ultimately they all recovered although some had to have significant burn treatment.

[stj]

Re: Free wifi solution.

it's not about localised heating, it disrupts the body's own electrical system.

[tom66]

Re: Free wifi solution.

it's not about localised heating, it disrupts the body's own electrical system.

More bullshit, I see. Do you have any evidence of this? If such an effect was observed, would it be permanent damage or transient? This sounds like a temporary effect. Some people claim to be electrosensitive, but they don't seem to feel these effects until they are told about devices being near. In other words, it's a nocebo/placebo effect.

The body does not have an "electrical system". Nerves transmit signals through chemical signals. These create electrical potentials due to excess of positively charged sodium ions BUT electrical current and signalling is not directly used. High current can disrupt nerve and muscle operation, but RF currents are measured in the nanoamp range.

Is there a single conspiracy theory you DON'T believe in?!

[tom66]

Re: Free wifi solution.

Was on the train, couldn't look it up, but both your high power routers are 20dBm for EU. They can use 27dBm (500mW) in US countries due to FCC regulations being a little more relaxed.

http://www.tp-link.com/en/products/d...specifications

Of course if you change the setting in the router to say it is in US region, you will get 27dBm functionality. But you will be violating RF limits, and if running a business, possibly liable to fine/prosecution (given the EU has a system of "RF bounty hunters" who are paid 50kEuro per successful conviction for RF spec violation, it's a bad idea to try it...)

[synaesthesia]

Re: Free wifi solution.

@stj: Time to get that tinfoil hat on, because you're taking in far more than that every day without realising it.

And yes, I frequent an educational IT based forum

[stj]

Re: Free wifi solution.

Was on the train, couldn't look it up, but both your high power routers are 20dBm for EU. They can use 27dBm (500mW) in US countries due to FCC regulations being a little more relaxed.

http://www.tp-link.com/en/products/d...specifications

Of course if you change the setting in the router to say it is in US region, you will get 27dBm functionality.

as someone who owns a wa5110, i can tell you for a fact that the power level is "low,medium,high" it is not tied to any region settings.
all the region settings do is lockout channels 12 & 13 unless your in japan i think it is.

[tom66]

Re: Free wifi solution.

Consumers are really easily confused. So I'm not surprised dBm isn't the unit of choice. Also, don't you think EU customers will be a little pissed off if their router only did "low" and "medium"? They want a " high" setting... Even if it's lower in other countries. (Shh, don't tell them!)

I am certain the output power will vary as the region requires. Devices are tested to meet strict intentionally radiative limits. Violating those means you don't get the CE mark, FCC mark, etc. And if the company is later found to be putting the CE mark on the device that's non compliant then you can be sued (by the EU) and product may be recalled. This may be hard to do with Chinese companies, so the EU will target the locally based distributors as well (as they are jointly responsible for certification.)

Ultimately this is all a silly argument because you need 20-50W of RF microwave power to begin feeling the effects. And damage is through burns, usually external. Extremely high powers, like 10kW or more, could be fatal because of damage to internal organs. You would be cooked through!

[stj]

Re: Free wifi solution.

quoting dBm would be pointless on pro-routers that have sma sockets on them for use wih outdoor antenna's
the figure would be dependant on antenna+cable quality+length.

[tom66]

Re: Free wifi solution.

quoting dBm would be pointless on pro-routers that have sma sockets on them for use wih outdoor antenna's
the figure would be dependant on antenna+cable quality+length.

No, dBm is quite valid. That is the total system power at the SMA connector, which is all the router manufacturer can guarantee, provided the system is well matched using 50 ohm connectors, cables and antennas. (Which for coax from China is very much hit and miss...)

Antennas themselves may have a gain, but they can't increase the signal strength, only make it more directional. So if you have a 9dBi antenna, it doesn't make your 20dBm router a 29dBm router. It just means that in a specific point on the radiation chart, the transmitted power will be 9dB greater than the mean transmission power.

Technically, that means the power received will also be 9dB higher (notice, the units here are irrelevant, as I could also quote transmitted power in dBW and the figures would still apply.) So if you were to do a safety analysis, you could say that the power applied to the human body is higher, by 9dB. But, it's more realistic to take an average over a wider area, as we are typically going to be exposed to a large cross section of the antenna radiation pattern.

Theoretically, with specific superconducting antenna design, it would be *possible* to design an antenna that concentrated the power over an extremely small area. This could cause burns/damage/etc. (as damage is proportional to the power per surface area.) But there would be no reason for a manufacturer to do this, as it would be essentially impossible to receive the signal! (Such a gain would have to be around 50-60dBi to be dangerous.) Practically speaking, antenna gain is limited to around 10dBi, for the best most directional antennas. This is the same reason a 5mW laser pointer can cause blindness, the power is concentrated over such a small area so that it can damage the retina very easily.

[stj]

Re: Free wifi solution.

i'm pretty sure dBm is supposed to be calculated at 1m from the antenna.

[tom66]

Re: Free wifi solution.

i'm pretty sure dBm is supposed to be calculated at 1m from the antenna.

No, dBm is the radio output of the router or other transmitter. It is an ideal figure, usually with some tolerance around +/-1dBm or so, but dependent on the antenna/cable/connector being well matched.

You could measure it 1m away and get a valid dBm figure, but this isn't the transmission power of the router. The dBm figure there is affected by all sorts of other parameters, including stations nearby that create intermodulation distortion, and the design of your receiving and transmitting antenna, cable loss, receiver loss, and the exact symbols/data being transmitted.

[budm]

Re: Free wifi solution.

[omendata]

Re: Free wifi solution.

Ubiquiti UniFi AP Pro.

Two different ssids = two separate networks.

You get what you pay for - I've tested and installed most wifi gear and the Ubiquiti stuff really is impressive. Check out Linus on youtube he just did a similar fix for a restaurant in Japan.

If you want to go cheap I have found TP-Link to be extremely good equipment for such a small price - I believe its a Polish outfit but i know many installers use them for companies that want the el cheapo solution - who doesnt these days!

[yakideo]

Re: Free wifi solution.

You need two SSID's on two separate VLAN's. The public VLAN should only have access to Internet. You will need a access point that let's you setup a captive portal. Additionally you would want to turn on AP isolation, so that clients connected won't be able to talk to each other directly.

Setting this up incorrectly can create a big security hole. Also as someone already mentioned collecting personal information might be touchy depending on local law.