Trying to connect to open network, signal strength issue, looking for advices

HesusMD · Feb 18, 2015

Hello. Currently I have this(http://www.tp-link.com/en/products/details/?model=tl-wn722n#spec) wifi adapter with a stronger antenna(can't say how much DB gain does it have, cause it was given to me, but I just measured it, and it's 35 cm tall). I would like to catch a open wifi hotspot that is about 20-25 meters away from me, but the problem consists of 2 parts:
1) there's a rather big building in between my apartment and the bank from where the wifi signal is coming from, blocking the line of sight
2) since it's a bank hotspot, im guessing they use a different kind of glass, because my reception immediately outside the building was much poorer than one would expect. Inside the building I have maximum reception on my cellphone.

So, I'm thinking to buy some alfa device, something like this: http://www.amazon.com/Alfa-AWUS036NHV-9dBi-Magnet-Base/dp/B00LU48JTO/ref=pd_sim_pc_4/192-3926622-7483466?ie=UTF8&refRID=0PJQAKRZYM397WJXXVA8

Do you know it would help me catch it? I would only need about 1-2mbps link, not full 54. I'm a bit suspicious about that alfa receptor. I know it's a really huge brand name for adaptors who support promiscuous mode, but I dunno if I can believe it actually uses 5W amplification as it claims in the title. Isn't that like, illegal? I thought 1W is the legal maximum. Currently, I don't even see this hotspot in Windows, and just occasionally in airodump-ng.

bill001g · Feb 18, 2015

alfa tends to fib in their advertisements. Not sure why they play silly games like this but I tend to not buy their equipment anymore because of this. This is the fcc filing for that device. This requires testing to a standard and in these reports they claim to put out about 100mw..without antenna I think.

https://fcc.io/2AB87/8188

In any case your only hope is to use directional antenna to focus the beam...and where you can legally use more power. Lately the cost of ethernet bridges is the same as just a raw antenna. Look at ubiquti airgrid. Things like AG-HP-2G20 give a 20db gain in a direction dish for under $70.

Still it is highly unlikely this will work. As you noticed it takes almost nothing to block the signal. They put a film on the windows where I worked and we noticed exactly the same thing. It almost completely blocks the signal which is a good thing in some ways.

So if a thin metalized film you can see though can block the signal and then it must pass though a building you have no chance. A concrete wall does a much better job that some film of blocking the signal. Even if the other building has the same film it would cut the signal even more.

The main problem you have is even if you increase your signal levels the film/walls increase their rates of absorption.

When they put the film on there was a small area outside someone wanted coverage. We figured we would just turn the power up on the AP near that area...we do not run the AP at full power. What we found is even though we doubled the power the signal outside only increased by a very tiny amount.

HesusMD · Feb 18, 2015

bill001g :

alfa tends to fib in their advertisements. Not sure why they play silly games like this but I tend to not buy their equipment anymore because of this. This is the fcc filing for that device. This requires testing to a standard and in these reports they claim to put out about 100mw..without antenna I think.

https://fcc.io/2AB87/8188

In any case your only hope is to use directional antenna to focus the beam...and where you can legally use more power. Lately the cost of ethernet bridges is the same as just a raw antenna. Look at ubiquti airgrid. Things like AG-HP-2G20 give a 20db gain in a direction dish for under $70.

Still it is highly unlikely this will work. As you noticed it takes almost nothing to block the signal. They put a film on the windows where I worked and we noticed exactly the same thing. It almost completely blocks the signal which is a good thing in some ways.

So if a thin metalized film you can see though can block the signal and then it must pass though a building you have no chance. A concrete wall does a much better job that some film of blocking the signal. Even if the other building has the same film it would cut the signal even more.

The main problem you have is even if you increase your signal levels the film/walls increase their rates of absorption.

When they put the film on there was a small area outside someone wanted coverage. We figured we would just turn the power up on the AP near that area...we do not run the AP at full power. What we found is even though we doubled the power the signal outside only increased by a very tiny amount.

Thanks for a really thorough reply. I am just wondering, why weren't you using your APs at full power? Cause of possible radiation? A few flowers in my house that were just next to AP died in a matter of months.

And I've looked up the atenna u mentioned, does it have an amplifier in itself or? Would I just plug it into usb wifi adapter.

bill001g · Feb 18, 2015

It plugs into a ethernet port. It got the antenna and all the electronic in the antenna designed to mounted outdoors. If I remember right it can actually act as a router but it is mostly used as a bridge. You would either directly hook a pc ethernet to it or you could hook it to a router.

In a commercial building you have lots and lots of AP so you can have fewer users per AP. The problem is the signals interfere so you turn down the power so only the users close to it can use it and the users close to a different AP use that one.

HesusMD · Feb 18, 2015

bill001g :

Right, that makes sense. I found this, http://dl.ubnt.com/guides/airgrid/airGrid_AG-HP-2G20_QSG.pdf, reading it, nice stuff.

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Trying to connect to open network, signal strength issue, looking for advices

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