Sharing wifi between buildings

[JRX]

I got a friend who lives 2 blocks from my house, he is in a only-student building and they got 10Mbps ADSL. He has no prob to share it with me, but obviously this is impossible, becos no Wifi antenna could reach such a distance.

The thing is, i heard you can connect to a distant hotspot using a standard Directtv dish. Is that true? or just another myth? you only need the antenna or some other equipment? (i bet you need a modem with coaxial cable support)

Ph33r my....3r...w41t...

 

[palmerg]

Its possible to do with the proper antenna. However, you would need significant power to drive the extra gain (at least 20db). Those are difficult to find and expensive to build. The DTV dish may server in this capacity if you found the proper power and the specialized Equipment to 'extend the 802.11g signal ( 11.g would be recomended). Oh and you would probably need clear line of sight with no obstructions of any kind.
Just an example. At DefCOn and Black hat this year in Las Vegas, the WIFI challenge winner transferred data using an 11.g carrier signal over 50miles. That took some major equipment.

 

[kwebb]

You need line of site but you certainly don't need 20 dB of gain. For two blocks you don't need a very powerful antenna you just need it to be directed. A 5 dBi yagi would be fine as long as you have a short pigtail from device to antenna. Two blocks is nothing, with the understanding you need good line of site.

 

[palmerg]

Not in my experience. Perhaps 20 is overkill but 5 in most cases won't maintain a connection at any significant distance, I suppose it somewhat depends what he means by "block". A rural blocks vary a lot. City blocks he is talking a greater distance.

 

[JRX]

Yeah, in fact i got the idea after that convention, but i couldnt find details or a howto guide.

The path is clear of any kind of barrier and the local weather is dry (havent had fog in years), and theres no cellphone or other satellite antennas, so the signal should be pretty clear.

Ph33r my....3r...w41t...

 

[kwebb]

20 db is more than a bit overkill. Well can't speak to your experience but I've put up several hundred links of what would amount to a city block. Hell a couple of city blocks with 4 dBi patch antennas. Not even a very tight beamdwidth. Get a yagi with a 30 degree beamwidth and and at least 5 dB, you could go 7 if you want some confidence. Not a problem.

 

[palmerg]

Looks like my experience isn't the norm and Kwebb is more correct. Some proof of this can be found <A HREF="http://www.wirelessnetworkproducts.com/index.asp?PageAction=Custom&ID=20" target="_new">Here</A>
Still digging up a useful howto but its really not that difficult.

 

[JRX]

This is a (small) city and the blocks (at least in this neighborhood) are 50 meters long per side and the streets are 10 meters (and up) wide.

What is a yagi? its like a frequency modulator?

Should i just hookup the antenna to a wifi router with coaxial port or I'm missing some other equipment?

Ph33r my....3r...w41t...

 

[palmerg]

Got low budget and the spirit of adventure? Build a Cantenna.
Check this out. Its a pretty good how to for a number of items you might need. I'm gonna try and build one.
<A HREF="http://www.turnpoint.net/wireless/cantennahowto.html" target="_new">http://www.turnpoint.net/wireless/cantennahowto.html</A>

good luck!

PS: That article also has an answer to you Direct TV questions <A HREF="http://www.wwc.edu/~frohro/Airport/Primestar/Primestar.html" target="_new">http://www.wwc.edu/~frohro/Airport/Primestar/Primestar.html</A>
Keep in mind that that solution will share his WiFi with a good portion of the neighborhood as well as you <P ID="edit"><FONT SIZE=-1><EM>Edited by palmerg on 02/11/05 08:46 AM.</EM></FONT></P>

 

[JRX]

Haha i cant believe it! a pringles can?
Damn,is too cool and weird at the same time . I knew you could built something like that, but working as good as a dish or a normal antenna? its just amazing...

BTW i bet a steel bowl would do the job better than that, plus you get no corrosion and aesthetic issues

Ph33r my....3r...w41t...<P ID="edit"><FONT SIZE=-1><EM>Edited by JRX on 02/11/05 09:09 AM.</EM></FONT></P>

 

[palmerg]

don't know about the steel bowl. The wave guide formula sort of depends or is based on the confined shape in this case a cylinder. The 1/4 waveguide calculation would not help you accurately place the connector in the bowl. You are welcome to experiment away.

 

[JRX]

Good point, there's cylinder-like bowls too, but seeing the classing dish layout of the normal bowl makes me thing it could work.

I`ll post my experiences in the future.

Ph33r my....3r...w41t...

 

[kwebb]

"Looks like my experience isn't the norm and Kwebb is more correct. "

I'm not trying to be ugly but what is described in this thread is what I did for a living for close to 5 years. A 20 dBi yagi would be an enormous waste of money. Frankly there is no debating that although I do understand others experience doesn't really match mine however I had the advantage of using excellent equipment and a very high volume of opportunities to do just what is described in this thread. These kind of short shots were boring really after a while. Now creating a steady 10 to 20 mile link (with less than 20 dBi directionals sometimes by the way), that was always fun.

 

[palmerg]

ok, I have no problem conceeding to your expertise on this. My experience, which is basically doing war driving experiments sponsored by a gvt lab to see if folks were complying with WEP/WPC policy, is certainly not as credible for this thread. The antenna used in my situation was built by some antenna geeks who may have had a secret pact to max out db. I made an erroneous assumption that because that antenna was ~22db and that we were monitoring from various distances between 100 and 500 meters that what I quoted was credible.
I am not an expert on this by any means, but I am learning.
Thanks

PS: it seems that a yagi may not be necessary to accomplish what he wants to do.<P ID="edit"><FONT SIZE=-1><EM>Edited by palmerg on 02/11/05 01:09 PM.</EM></FONT></P>

 

[kwebb]

You can do it without a yagi yes. Panel, patch omni. Several options there but frankly I'd probably go with a yagi. Just not a home made variant.

 

[palmerg]

I just think that for the cost versus the performance some of these Cantennas we're seeing (granted they weren't competing against commercially manufactured units) were very nice and would certainly be more economical, not to mention fun - it seems the original poster is up to the challenge too.

<P ID="edit"><FONT SIZE=-1><EM>Edited by palmerg on 02/11/05 04:05 PM.</EM></FONT></P>

 

[folken]

I built a 36oz yuban coffe can cantenna and it works great. It was very easy to make too bec the bottom ridge on the can is actually almost exactly where the little N plug thing needs to go
I have the can pointed at my neighbors house so I can connect to my network when I'm over there helping him with something. When I'm at his house I am probably about 200ft away and behind about 4-5 walls. I could only sometimes even see my AP (WAP54G) w/ the stock antennas. When I put the 36oz coffe can on it I could connect right up and keep a fairly decent signal. I'm sure it would have max signal if I had a can at each side and no walls between them.

The N connector and pigtail cost about $10 online and my neighbor gave me the can. Not to bad for a $10 antenna

<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>

 

[palmerg]

2 Qs. 1- did you have to do much focusing between the two loactions or just sort of point it in the general direction?
2- What is the general orinetation of the Wire element inside the can? The article seems to say that most work best if it is almost straight up and dowm or almost at right angles to the ground.
This is really interesting. I am definately building one and the reasons you do it is a good one for me as well since I have been known to get a call from a neighbor about fixing their computer too.
Also, how can you beat the price? Assuming I do a competent build job.

<P ID="edit"><FONT SIZE=-1><EM>Edited by palmerg on 02/11/05 09:54 PM.</EM></FONT></P>

 

[folken]

I just pointed it at the general location of his computer room at his house. It is pretty easy to adjust it, just turn on netstumbler and walk back and forth watching the graph. The peak is where it is pointing
The little piece of wire should be as straight up as possible inside the can.

<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>

 

[JRX]

You know, this low budget antennas make possible to build a private network between houses blocks away one of each other to share data and other resources. It only takes some common APs and the cantennas to interconnect a whole campus or a medium neighborhood.

Back to the topic, do you really thing that the can is the best thing available? My only real concern is corrosion (and having to replace it too often) what about a stainless tube? or a steel cylinder?

PD:back to the dish, cant it be modified the same way as the cans?

Ph33r my....3r...w41t...

 

[folken]

Using some kind of steel can is just the cheapest solution. Any sort of metal can will work. If you can find a stainless can it will work fine. You just have to make sure you correctly calculate where to put that little copper wire inside the can and how long to make it.

The dish thing is basically removing the little reciever that is on that arm and replacing it with a small can (like a soup can or something). The dish just better directs the signal.

<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>

 

[JRX]

Stainless cans are pretty weird, basically becos most people trash the cans (ergo, they aren't intended for a long-last use)

I could use a aluminium pipe (in fact, i think the signal will be better with that) instead of the can.

I just mentioned the dish becos i have a spare one (the other is in use) and the better the signal quality is...

BTW, searching for a good can i found a weird lettuce dryer in my parents kitchen. It resembles one of those mechanical satellite antennas from the 80s. The best part is that is already has a hole right in the middle for the wire (one thing less to do) and its pretty small (laptop sized dish XD). Just one thing: its full of little holes. Not that the entire structure is made of holes, but its has 1 for every 3 and a half MMs.

Does that affect the signal?

Ph33r my....3r...w41t...

 

[folken]

I found one of those things too! Never even thought about making it into an antenna, lol. I don't know about putting the little wire in that hole in the middle though. I think in a dish setup you need to make a small cantenna and point it at the dish to focus the signal. I'm no pro when it comes to wireless stuff, putting the wire in the middle might work for all I know lol. I've just never seen it done that way.
I've seen lots of dishes with holes in them. The ones I've seen were probably carefully placed though. Just cover the thing in aluminum foil or something, lol.
The other problem that might arise is that a lettuce dryer was not made to be a dish in any way shape or form. You will probably have a heck of a time getting everything calculated right. Such as the curvature of the dish, how long the arm needs to be, how big the can needs to be, etc. It is much easier if you start with an actual dish, then you just need to put a cantenna on it's little arm and you are good to go

<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>

 

[palmerg]

I tend to agree. Read the whole Cantenna website, including all the links. Its very technical and describes the working of a waveguide antenna pretty fully. Variation is encouraged but within the constraints of a specifc formula. There is a link that explains the use of the Direct TV antenna to basically mage the directional waveguide antenna into a spread spectrum device. Can't mix and match the two, it seems to me.

 

[JRX]

Shape? no problemo! the cool thing about this lettuce dryer is that is adjustable for different sizes of vegetables, been able to fold into a semi sphere and having different degrees of aperture it can even emulate the shape of a can.



Ph33r my....3r...w41t...