Sounds like interesting work, although a little chilly...

In reply to a post by ian72:

Sounds like interesting work, although a little chilly...

I was 'kin cold, hitting -40 at times and it was during January and February! So we saw very little daylight.

2.4 ghz wifi can go a long way with the right aerials, a team some years back managed over 100 km ..

On the 5 Ghz band you can go even further as the noise floor is lower and aerial sizes per gain more manageable.

We rely on such links that run 30km+ every day here

the biggest issue is the ack timing. domestic wifi kit has a fixed distance limit, the acknowledge timeout.

this is how long after one end sends a transmission it will wait to expect a reply. this time increases with distance (speed of light) . if the timeout is fixed to short range then longer distances will cause the system to keep tripping over itself and re-sending data.

dynamic ack timing means the system works out the link distance thereby allowing more time for a reply.

In reply to a post by eckiedoo:

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?

Thanks very much Bill and others

Interesting what such an apparently simple question brings to light.

I have experience of 10 GHz, with 154 and 105 Dipoles, respectively Azimuth and Elevation, fed from variable-width waveguide, for Ground Controlled Approach (talk-Down), MPN1A, back in the late 1950s.

The beam widths were 2 Degrees by 0.5 Degree, achieved by the large number of dipoles, swinging over arcs of 10 Degrees from the variation of (guide) wavelength within the variable-width waveguide, so changing the phasing of the drive to the dipoles.

Normal working range was 10 miles, to cover the Final Approach, there being a separate 3 GHz Search system out to 30 miles, to talk the pilots round in to the Precision beams above.

With a lot of careful tuning, cleaning of the rigid waveguide feeds etc, I did get the 10 GHz Precision system working out to 30 miles. The variable-width waveguide was too complex to play with.

Arthur C Clarke, the later Science Fiction writer, was involved in its development and being put in to service during WW2.

His 1964 book, "Glide Path", describes his experiences.

In reply to a post by MrSaffron:

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 there used to be quite a few DIY designs for waveguide aerials using food cans etc on the internet .
I suspect the main problem with highly directional aerials at both ends is actually getting them even roughly aligned .

In reply to a post by rarrar:

In reply to a post by MrSaffron:

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 there used to be quite a few DIY designs for waveguide aerials using food cans etc on the internet .
I suspect the main problem with highly directional aerials at both ends is actually getting them even roughly aligned .

I've seen it working with a Pringles Tube cut down.

When I looked after the local charity run schools computer network for free I set up a WiFi link using two Satellite dishes with a WiFi dongal at the focal point, one at the school high up on a chimney and another on the end of our house high up in line with the school over 1kilometer away.
From that I could remotely run the Network

This is a good site for idea's http://www.wlan.org.uk/antenna-page.html

Thanks Aptman, some interesting aspects coming to light!

To be honest though, I had raised the question thinking in the unstated terms of ordinary "domestic" WiFi, and wandering around in the proximity of one's home.

Another useful cheap way of boosting WiFi around the home etc. is to use some old WiFi modems/routers (I get mine free off freecycle ) and set them up as 'Access Points' (get details off the web to do that !).
I have a very large house and garden and good WiFi is available all over.

Thanks, Aptman.

I have done that experimentally; but normally would not need to do so.

I also have Connectify on my various portable PCs, so if necessary could also readily extend that way - but normally it is switched off.