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Posted by:dragorn
Subject:Antennas for Kismet and wardriving. Questions.
Date:13:42:05 05/10/2011

> 1. Do I need an antenna? I understand that the laptop might not get all networks because it is in a car, but I don't need every network around for statistics. Or on the other hand, could the encryption type or manufactorer of the network(router) have anything to do with me not detecting the network, rendering the statistics wrong?

You'll usually see an order of magnitude difference between the laptop antenna inside the car, and any sort of antenna/radio outside of the car.

> 2. Most webpages mentions omni-directional antennas. And on Kismet forum I have read that 5db should be the most preferable. Is this what I need to buy?

Yeah - the higher the db gain on an omni, the 'flatter' it is. It starts as basically a sphere and eventually turns into a pancake, so you'd miss anyhting above or below the plane the antenna is on.

Factoring in the cost of antennas, the cheapest route might be to get an Alfa from Amazon (or whatever vendor is cheapest in your area), throw it in a plastic bag with a magnet, and throw it on the roof. That would probably run you about $40-$50US, eliminate cable loss for the antenna, give you a NIC you can connect arbitrary antennas to, etc. If you go this route, get the 5db gain ones, not the crazy foot-long antenna models.

> 3. Mostly, I read about antennas together with wireless network cards. Can I just buy an antenna for laptops which plugs into the laptop with a usb? Or will this complicate things and therefore my best option is a wireless network card with an antenna?

You can by a card w/ an antenna jack (see above) that plugs in over USB. Otherwise, you'd have to modify your laptop, drill a hole, get other cables inside connected to the NIC, etc.

> 4. Is there a connection between the GPS and the antenna? Or do they "meet" for consultation inside Kismet? Sorry, couldn't really phrase this better.

You can get a GPS antenna, but that's independent completely of your wifi stuff. GPS runs around 1.3GHz, wifi runs at 2.4 or 5ghz. The GPS by the time it gets to your computer is just a serial line (usb serial or rs232); all the radio logic is handled in the gps rx unit. Again, you'll probably see a nice boost in signal fidelity/lock time if you put the gps on the roof, there are a lot of cheap USB bluetooth devices which are waterproof and stick on the roof of the car, if you wanted to go that route.

> I have read the README file, but I can't see too much about antennas. I searched the forum for antennas, but very posts emerged. I have read on many websites and forum posts through google, but I really don't know if the person answering is nonchelant about the information he or she gives out or if they really know what they are talking about. Just my own thought, since a lot of what I have read contradicts each other. So, my safest bet is Kismet forums.

I usually tell people stick in the 5db range, definitely below 8db, for an omni.

It kind of depends what your goals are. If you want to try to position networks and survey them, you want an omni. If you're trying to just collect as many networks as you can, then multiple radios, amplifiers, and a combination of omni and directional will find you more networks, but will corrupt the positioning info (since you only know where you are, putting a high gain directional will pull networks from arbitrary distances and map them to your location artificially).

I suspect an Alfa in a baggie stuck to the roof with a magnet will get you a very good sampling. If you want to be fancy and have the budget, get multiple cards - kismet will sort things out so they don't overlap and you'll get more channel coverage at any given moment.

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