Your opinion on attennas

Your opinion on attennas

Postby Chris_Schear » Sun Sep 08, 2002 3:40 pm

I've read almost every link I've found on constructing homebrew antennas; pringles cans, coffee cans, etc. I even read the http://www.turnpoint.net/wireless/has.html link that compares different types of cans. What I'm interested in is given your personal experimentations with external attennas, which you have found the most usefull for WarWalking.

Now, just because a particular type of can might give you the greatest range, it might be akward walking around the office parks with a 500 gallon drum you've constructed an antenna with and stapped onto your back with industrial strength nylon. So, from a corporate network security persepctive, if your mission is to seek out and SPECIFICALLY isolate where wireless access points lie - which can/antenna do you think is best suited for the job? The goal is to be able to essentially "point and click", and find/walk up to rogue access points.

Thoughts?

I'm inclined to think a can with a narrow diameter is best suited, so that it may be "aimed" more accurately. The last thing I want to do is walk around 9-some odd, 30+ story buildings..."guessing" at where rogue access points are located.
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Postby Eyecannon » Sun Sep 08, 2002 4:15 pm

Now that would be cool, if you could get GPS to work inside a building... you could use the elevation info available to map out a 3d path of where you were in the building :p

Anyway, different antennae do different things... one guy recently used a panel antenna in his backpack with some good results... I have been thinking of using my magmount in a backpack (hopefully it won't kill me!) It might be a little weird if you were walking around a building with a cantenna aiming it all over the place :p
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Re: Your opinion on attennas

Postby rogerRabbit » Sun Sep 08, 2002 4:39 pm

You want directionality and, as you're interested in tracking down a site rather than maintaining a useable (hand-held) link, probably as much of it as you can get. By the sound of it, discretion is not an important factor for you ;) .

Using a cantenna, I'd go for a diameter of circa 3.75" and a length of at least 15". The diameter is more or less a given for 802.11b frequencies and the relatively longer length gives a higher gain/narrower beam. A shorter length (e.g. 6") makes isolating sources a slower process with low-rise buildings. I haven't tried with high-rise, but I'm sure I wouldn't be able to get a good guess, externally, as to a range of floors with just 6".
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Postby Chris_Schear » Sun Sep 08, 2002 4:39 pm

What I need to construct is an antenna what I can "aim" and walk. Stand somewhere, recieve a signal from an AP...slowly turn and determine what direction the signal is strongest from, hopefully indicating what direction the AP is.

"By the sound of it, discretion is not an important factor for you."

- No, it isn't...but I don't want to be lugging around some huge can, if some soup can will do the job :)
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Postby Eyecannon » Sun Sep 08, 2002 5:50 pm

Soup can is too short... but lots of people use pringle's cans!
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Postby Chris_Schear » Sun Sep 08, 2002 5:56 pm

Given your recommendation of lengths, I'm thinking a Pringles can is the way to go.
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Postby rogerRabbit » Mon Sep 09, 2002 1:44 am

Originally posted by Chris_Schear
Given your recommendation of lengths, I'm thinking a Pringles can is the way to go.


Too narrow! Solder/conducting tape three cans of the correct diameter together.
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Postby az2k » Tue Sep 10, 2002 1:21 pm

A regular soup can is too short but the larger Campbells can (family size or something like that ) is OK. It is the same size as the Hunt's pasta sauce can shown at turnpoint.net I made a cantenna using the Hunt's can and it works very well. The can is on the short side based on its diameter of 3.25" but it works.

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Postby Sh00t3r » Tue Sep 10, 2002 1:27 pm

The best results i've attained through warwalking is using my home brewed omni and then switching to the pringles can for a more directional view. Seems to work good.
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Postby Chris_Schear » Tue Sep 10, 2002 8:59 pm

Thanks for the feedback.
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Postby astcell » Mon Sep 23, 2002 3:21 pm

Let's say you're out at the Block at Orange where there are plenty of hi rise office buildings around. Of you are in NYC. If you had a good yagi, could you conceivably point it at all the windows on the buildings, all 40 floors maybe, and get any APs that may be out there? Or do they broadcast enough so that being at the ground floor would pick them up?

I'm trying to figure out the best way to stumble when hi rise office builsings are involved, surely there may be plenty of APs in those!
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Postby blackwave » Mon Sep 23, 2002 3:53 pm

Originally posted by astcell
I'm trying to figure out the best way to stumble when hi rise office builsings are involved, surely there may be plenty of APs in those!


two words,
bungee cord
helmet optional
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Postby RaVenCorax » Mon Sep 23, 2002 5:34 pm

why use a soup can or a pringles can i know some one you know does sheetmetal its not that hard to make a perfect cantenna just give em the dimensions and a few dollars stainless with mounts and predrilled holes
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Postby astcell » Mon Sep 23, 2002 6:26 pm

I agree! THe plans I have see online for Pringles antennas are vague in the parts listing. "2 inches all-thread" is not really an item by that name, you need more info!

I would love to see a difinitive parts list, just like turning your AR-15 into an M-16. Information overload baby, that's the name of the game.

I wonder if offering a reward for a 50db antenna would be a challenge to anyone, and what $ amount would entice folks...
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Postby RaVenCorax » Tue Sep 24, 2002 6:30 am

sinve people are always bitchong and going on about pringles can no being metal and soup cans to short make your own or pay someone to make the perfect aize what is it 3.75 inches and 16 in long

yellow pages peoples
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