Maximum WiFi Range

I am studying with FutureLearn, and on the course "Cyber Security", the question of WiFi maximum range has come up.

One of the other participants has posted this comment-
"
Not sure your are right in saying wifi has a very limited range. I have picked up a wifi signal and logged on to it from a distance of two miles. Admittedly I had an aerial but so could any hacker!
"

Apart from possible confusion such as BT FON multiple Hotspots, have any of you any experience of such long distances?

With appropriate antenna yes this is possible presuming you have a clear line of sight and the output from the Wi-Fi source is sufficiently directional too.

Take a look at the various Wi-Fi kit for long distance links sold by www.solwise.co.uk

Also it helps when you have a directional antenna as well, just means that you turn the beam until you get a strong signal.

Paul

Thanks to both of you.

http://www.solwise.co.uk/downloads/files/linking-bui...

Section 1.3 with its table is interesting.

Although I find 5a and 5b apparently contradicting the norm.

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I am trying to get more information from the other course student.

In the meantime, I would appreciate comments from anyone with practical experience of such longer distances for Wi Fi, whether intentional, ie with equipment intended for such ranges; or "unintended".

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It can be amazing what happens with radio waves.

Many years back, I was listening to two radio amateurs, one "just down the road" in Edinburgh, the other in New Zealand.

My aerial was the proverbial "short piece of string" to a clothes pole in the back garden, hemmed in all round by buildings.

I don't know the NZ amateur's rig; but the Edinburgh amateur was a Cemetery Superintendent and his various aerials effectively were well clear of any buildings etc, with a public park across the road.

I had no troubles picking up both; but the Edinburgh amateur was having great difficulty receiving the signals from NZ.

In reply to a post by eckiedoo:

Thanks to both of you.

It can be amazing what happens with radio waves.

Many years back, I was listening to two radio amateurs, one "just down the road" in Edinburgh, the other in New Zealand.

My aerial was the proverbial "short piece of string" to a clothes pole in the back garden, hemmed in all round by buildings.

I don't know the NZ amateur's rig; but the Edinburgh amateur was a Cemetery Superintendent and his various aerials effectively were well clear of any buildings etc, with a public park across the road.

I had no troubles picking up both; but the Edinburgh amateur was having great difficulty receiving the signals from NZ.

Yeah, I just love listening and talking to them, I have a tri-band (5m, 2m and 70cm) vertical antenna on the roof along with a long wire (doublet HF) antenna across my garden, now the home made wire antenna can contact people all around the world on anything from 10W to 50W by bouncing the signal, however people down the road cannot or have issues hearing me

Paul

Directional antennas concentrate the beam so have a higher field strength at the transmitter and thus higher all along the path when compared to a a basic Omni. A directional received will again concentrate the received signal and effectively amplify it.

Two miles could be achieved with a clear line of site and good antenna ... I believe some experiments have actually achieved even more.

I have done quite a lot of work in the 1.6 - 1.8 GHz band and that is good for 40,000km (25,000 miles) with around 10 watts. So, 2 miles at 100mW should not be an issue - with the right equipment.

At 25,000 miles the curvature of the earth must have a pretty big impact? Is this off high masts (presumably 4Kms high each to get line of sight) or using some form of orthogonal frequency division multiplexing or air to air/surface to air?

Have experience of getting an installation to connect 2 buildings over a small hill at about 10 miles distance where they used orthogonal frequency division multiplexing to improve signal strength.

Of course lower frequencies can give better distance/ability to get through obstacles.

Edited by ian72 (Tue 17-Feb-15 14:19:50)

In reply to a post by ian72:

At 25,000 miles the curvature of the earth must have a pretty big impact? Is this off high masts (presumably 4Kms high each to get line of site) or using some form of orthogonal frequency division multiplexing or air to air/surface to air?

It could likely be very high i.e. surface to (near) vacuum.

In reply to a post by jelv:

In reply to a post by ian72:

At 25,000 miles the curvature of the earth must have a pretty big impact? Is this off high masts (presumably 4Kms high each to get line of site) or using some form of orthogonal frequency division multiplexing or air to air/surface to air?

It could likely be very high i.e. surface to (near) vacuum.

Think you could be on to the right thing. Looks like geosynchronous orbit so presumably satellite comms. Makes for an easier line of sight capability if the satellite is always directly (ish) over your head.

Correct ...


GeoSync is 35,786 km above the equator and if te transmitter is at around 75 deg N or S and offset by 50 deg of longitude it will tend towards 40,000 km.

I spent time in the Arctic working and testing the transmitters where the elevation to the satellite at a couple of metres above ground or sea level was getting close to 0 degrees.