WiFi amplifiers. Good or bad.

[gm10]

Of course those things are illegal, wireless communications are tightly regulated because everybody has to share the spectrum. I don't know specifics for the UK but running a rogue transmitter will result in expensive fines, and if you disrupt other people's wifi you open yourself up to claims for damages. If you do that in the city you're almost certain to be found out. Or at least you would be where I live (not the UK).

Go with a legal wifi repeater.

[gm10]

I'm in the EU, and I think it's pretty clear from my post that I never used one, nor am I planning to, no. I live in the city though and I have seen the vans they use to triangulate rogue transmitters, so I know they'll come after you. It's not like you can cover it up, you're basically setting up a new cell tower.

But sure, of course they work and if you're in the countryside it's possible nobody will mind.

[JeremyB]

Wifi extenders might be legal, they plug into an electrical outlet but do need some info entered for them to work

[JeremyB]

They are bi directional, like a repeater

[Pjotr]

Why expose yourself to dangerous radiation levels? Better reduce them instead:
https://sites.google.com/site/easylinux ... -radiation

[AZgl1800]

worrying about the power of your WiFi adapter is pretty much Nonsense.

Unless you stick your head inside the microwave oven, you will not receive enough radiation to ever worry about the consequences.

I have been using radios as a Ham Radio operator since 1958, most of the time at 100 watts, and often at levels of 1,000 watts of radiated power.

I have never felt my skin get warm, and there has been no negative effects to my health.

X-rays from a machine, yes, you should always put on a lead vest, those frequencies can hurt you bad, and the power levels are high enough to hurt you...

even so, I have had well over a 100 dental x-rays during my 75 years, and none of them have had an adverse effect.

[AZgl1800]

Yes,

all they are doing is using a Yagi antenna to increase the Effective Radiated Power / Increase Received signal gain

at best, their hand held yagi antenna will provide them with 9 dBi over a standard monopole antenna.

Using a Yagi antenna for War Driving is a loosing game though, they would have to actually stop and aim it at your house, or the Time to catch a signal would vanish so fast, their WiFi receiver would never see your signal.

My guess is, during War Driving, they are watching an analog signal display, and when they see one, they stop and switch over to a Yagi antenna while stopped.... then their signal could swamp out your WiFi receiver so that their adapter is inserted in the data path....

[AZgl1800]

I currently have my adapter and router set as TW Taiwan. This ups my power from 20dBm to 30dBm and gives me the 13 channels that are the default for GB, perfect. Wouldn't it be sensible, in light of this attack method, to set your router at the highest possible setting to make it more difficult to overpower?

you are confusing Transmit Power with Receiver Sensitivity.

they have no correlation to each other......
your WiFi transmitter could be putting out 1000 watts, but your receiver is still the same old radio it was before, so another War Driver with a Transmitter and Yagi antenna pointing at your radio/house can easily swamp your WiFi receiver with a strong signal....

a more powerful Transmitter will help you get more distance to the other WiFi radio's receiver....
but, your WiFi adapter's receiver must have a very low Noise Floor environment and a very good expensive receiver PreAmplifier.... you only see those in expensive commercial equipment....
Good PreAmplifiers have Super Cooled environments, like down to Zero Degrees Kelvin..... or -400 some odd degrees Centrigrade ( can't recall exactly what the ratio is )

those kind of receivers are only used for Space Communications with stuff way out there, like around the planet Pluto and beyond.

[AZgl1800]

I would have thought that if my router were sending out a signal at 30dBn then what would happen is that I would likely see two AP's with the same name. One genuine the other the imposter. I understand how the receiving radio can be swamped but I am still transmitting a powerful signal of my own, how is that swamped.

your adapter's receiver will lock onto the strongest of the two signals, and that would be from the very local War Driver's position. this is a very common thing to happen.

I am quite sure, you have driven down a highway with your FM music radio listening to your favorite FM radio station, and suddenly the music disappears and your hear people talking. On the same channel you are tuned to. this can happen quite rapidly as the car moves along the road. It is related to the Wavelength of the signal and the placement of the barriers along the road.

the 1st signal temporarily is overcome by the 2nd signal which is stronger for a brief instant.

[BG405]

How about directional WiFi antennae? These can give a decent range - several miles according to some accounts - without exceeding legal ERP levels (and/or using something which bypasses regulations & therefore may not provide a clean, properly filtered signal according to those regulations).

Just my 2p worth.

[AZgl1800]

How about directional WiFi antennae? These can give a decent range - several miles according to some accounts - without exceeding legal ERP levels (and/or using something which bypasses regulations & therefore may not provide a clean, properly filtered signal according to those regulations).

Just my 2p worth.

Ummmm,

unless my brain is really fogged up, I do believe that is what a Yagi Antenna is.

Forward gain of up to 26 dBi and backside, or off the Reflectors can be as low as 3-5 dBi
depends on the builder's design and method of construction.

[BG405]

@AZgl1500 - yes, indeed. I've seen little dish antennae as well which, if I recall correctly, could be used with a laptop & were slightly less .. ahem .. obvious!

I'm wondering whether to buy (or make) a Yagi & adding an antenna connection port to the netbook, or a dish. The latter would be easier as it could use an existing dongle & plug in to USB, but I can't find mine .. typical!

[jimallyn]

People have run wifi connections over 300 kilometers. Not sure about ERP limits here in the US, but there are ham frequencies in that range, so if you run it on one of the ham frequencies, the ERP limits wouldn't apply.

[AZgl1800]

People have run wifi connections over 300 kilometers. Not sure about ERP limits here in the US, but there are ham frequencies in that range, so if you run it on one of the ham frequencies, the ERP limits wouldn't apply.

hmmmm,

that will get you a nice notice in the mail from the FCC
no Commercial operations are allowed on Amateur Radio Frequencies.
and it would exceed the Bandwidth Limits allowed very fast.

[BG405]

300Km? That's impressive (about 186 miles) but how many packets made it through?

Great idea, BTW. Latency might be an issue with some stuff though.

mmmm,

that will get you a nice notice in the mail from the FCC
no Commercial operations are allowed on Amateur Radio Frequencies.

I assumed Jimallyn was referring to amateur operations. Or, at least I hope so.

[jimallyn]

Which bandwidth limits are you talking about? For 70 cm and above there is no bandwidth limit other than stay within the ham band, and follow good amateur practices. Some of the HamWAN links in the Puget Sound area reach 300 Mbps. I wouldn't be surprised if there some with higher data rates.

[GS3]

Recently ordered a cheap WiFi amplifier from Aliexpress and was wondering if they are any good?

Depends what you want to use it for but many or most people I know are disappointed by them and that is because they do not understand exactly how they work or what they can do and what they cannot do.

I've been told that the one I have coming is illegal to use in the UK but...

And the reason they are illegal is usually because they can interfere with other people's WiFi's. Unless you are way out in the country and have no nearby neighbors I would say it is quite inconsiderate to use it.

There are many factors to consider as they make a big difference. One is WiFi density around you. If you are alone in the middle of the country you can connect to your access point from quite far away but if there are other WiFi signals present they will interfere.

It is different if you are trying to cover a wide area than if you are trying to get coverage in a small area located at some distance, like, say, a barn.

I have some years of experience tinkering with this and every case is different and you need to understand and take into account all the variables.

People who buy a "WiFi range extender" are very often disappointed by their performance. Often simpler solutions can give better results.

[BG405]

The WiFi amplifier in question is being held by customs

Could be a cause for concern, especially if it doesn't exceed the duty threshold.

I don't believe they are illegal to buy or import

Probably not; like those video senders you used to be able to buy.

just to use in certain situations.

Certain situations include use within the UK.

[AZgl1800]

Received the amplifier this morning and after a quick test I would say that signal strength is boosted by around 20%. There is a down side, when using my connection it seems slightly less responsive. Perhaps that is a trade off. I am going to try the dipole antenna as have been testing it with a small yagi.

That less responsive is because you have inserted a repeater in the middle of the transmission path.

probably a small cost to you , for the added signal strength, the dipole will be weaker than the yagi by about 9 dBi ( assuming a typical hand held yagi, not a super long boom type )

[AZgl1800]

yeah,

I won't buy anything w/o removable antennas.

I can't predict my future needs all that well