Wi-fi range is limited due to govt rules and regulations
but still 
Which hardware or set of hardware I should use to beam wifi hotspot to cover 1KM radius?
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Omnidirectional, an 1 km radius? Forget it. Even if you could get that magical access point approved and get it to yell Wifi with the necessary volume, regular devices would not be able to answer back.
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If you need to bridge specific locations, you can use directional antennae and cover even longer distances than 1km.
The set of hardware is called a mesh network. ie a network of 802.11s meshnodes each with its own AP. By the way that's an area of 3.1415926536 square kilometres. If you put your meshnodes 100m apart, that's a lot of hardware 
Please send request for quotation. ... :pmsl: 
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And every node still needs power so if you are going to dig down a power distribution network for 1km, then just dig down the opto fiber instead from point A to point B.
But the thing is that you never distribute the wifi, you distribute the data from the router for 1km or 10km or 1000km. And then mount a AP at the endpoint.
You could use solar panels and just use the network when the sun is up... 
Ok, we get connection again in april…
If you live near the polar circle, yes, not everybody does.
If there's an old two wire copper phone line, you can use VDSL extenders, they can easily go 1+ km.
Yup, or get your mates to shine a torch on intermediate nodes.....
Yes but the op wants a 1Km radius hotspot not a 1Km point to point.
That's 8 concentric rings 100m apart. Now I need on old envelope and a set of log tables to work out how many meshnodes or vdsl links would be required....... 
Transmit is usually not the problem. The problem is with the reception. To explain myself, all radios are more or less capable to transmit the 20mW, but if the antenna connected to them is a lousy 2-3dBi then the receiving end cannot be very far, cause the amplification from the antenna will not be enough.
But if you have an omni with 7-9dBi at the access point, drop the transmit power to 10-13dBm and have a 20dBi directional antenna with 0dBm txpower at the client side you can go over 1km. Moreover the first km is quite "expensive" in terms of attenuation (about 100dB) while 2km add only 6dB extra (about 106dB) in total.
So when I was playing with wireless metropolitan networks in 2003-2010 we used some very directional antennas with as much dBi as possible.
not bridging specific locations,
I want to cover each point in 1km radius
All of the more positive remarks above have direct line of sight within the whole fresnel lens in mind, as well as roughly comparable equipment on the tranmitting- and receiving side. If either of these is not met, it's not going to work, at all.
So unless you'd be on a free field with no obstructions of any kind (and actually kind of on stilts), this is not going to work.
thanks all,
now I am wondering what is best router for 2.4ghz openwrt mesh network
I am thinking of installing multiple
CPE220 (openwrt mesh, not sure whether this router supports)
issues
- giving all nodes power is an issue
- it works well only if all two nodes are in line of sight without any obstructions
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If I put my serious hat on (sorry I was having a little fun at your expense 
)
Yes that's true, but if I take a guess at what you are actually trying to achieve, it is a solvable issue.
If you really want coverage of an entire circle of land within a circle of radius 1Km, then you really have a problem.
Assuming clear line of sight everywhere and 100m separation, it would break down to 8 concentric rings of meshnodes/APs depending on how you decide to connect it up.
A bit of maths will show you would need something like 2*3.1416*8!/100=2533 devices!
If your 1Km radius is centred on a village for example, the problem is much more doable - indeed has been done on many occasions.
A typical village with a 2Km diameter will have radial roads running from the centre with properties on or near the roads, getting further apart as the distance from the centre increases.
Here you only need "nodes" linking from building to building in line of sight, a much simpler problem, with each building with a "node" supplying the power and a dramatic reduction in the number of devices required to give coverage only where it is required and these devices do not need to be omnidirectional, thus giving even better coverage with an even smaller number of devices.
The Tplink CPE220 is probably good for this (it should be 802.11s capable), but is very directional so might need two at each location, back to back, to provide chaining out from the centre.
Its name is the giveaway - CPE stands for Customer Premises Equipment and is usually used in a WISP environment for point to multipoint links building a backhaul network
So it is still not a simple problem to solve. It needs a considerable amount of surveying/planning to give the coverage you are after
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Number of AP's seems to be about an order of magnitude to high ? Rasterlike would be more around 300 or so ?
Straight lines (rasterlike - a square with the corners rounded off) or concentric circles for a max separation of 100m would give pretty much the same number. Anyway, it was to indicate the non intuitive large number. Doing a backhaul with sector antennas over longer distances along streets with "user" CPEs is the way forward.
I'll get another old envelope and pencil and work it out again, just for fun
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Fully agree with your analysis, like the OP who marked this solved.
For reference - I like the question a lot in it's original form - I'd like to post a reference to a puzzle with solution approaches :
mathematics - Can you irrigate your lawn with 23 sprinklers? - Puzzling Stack Exchange
Particularly comment 3 (hexagonal elements) has elegance, and gives a nice approximation with some geometrical properties and assumptions.
Yes, you can beam wi-fi directly over a distance of a kilometer quite readily. You need:
- 2.4GHz WiFi adapters with the highest power output you can get. Highest one I've seen is 28dBm (~630mW).
- A high gain colinear antenna at the source. Generally this will look like along dipole, but what it is is a stack of linear-arranged dipoles. This flattens the output so it resembles a disc.
- A high-gain unidirectional antenna for each remote site. I've seen people make folded dipole arrays, but they aren't common. Easier to get and use would be a yagi.
- The lowest loss cable you can get. LMR400 is pretty big, but very low loss. The reason you want this is you want to mount the antennae as high up outdoors as you can. Elevation on the central node is more important than on the remotes.
Remember to mount the yagis sideways because colinear antennae (like all dipoles) are vertically polarized, and yagis are polarized in the direction of their elements.
I have used a two watt transmitter and a 24dBi gain yagi that I made myself which I held in my hand and pointed to talk to ham radio operators on the International Space Station. I guarantee you can easily get a kilometer with the above.
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