two patch antennae for vehicle?

The gear needed for wardriving

3 posts • Page 1 of 1

Postby argh » Mon Jun 02, 2008 12:55 pm

I have been a big fan of moderate gain omni magmounts for a long time. I also have to replace moderate gain omni magmounts every few years, from wear and tear. I am considering something different (or perhaps additional) for the regular wardriving vehicle.

What about two 6.5 db patch antenna, each semi-permanently mounted in the side windows of a full-size van? I would lose front/back reception, but I pretty much eventually drive past everything on the sides, anyway. This antenna is actually two 6.5 db antenna, each already with 48" of feedline. I am considering seeing if I can separate it into two antenna, and get them mounted inside the van, right in the side windows. It seems I have read before that some UV tint in auto glass can absorb _some_ freqs, but I am not sure about 2.4 Ghz. The plan is to have them fed to one card, and then still use omni for second card, when i have the opportunity.

My average driving is rural and medium size towns, about zero skyscrapers or anything over a few stories tall. Thoughts?

Postby i_do_dew » Wed Jun 11, 2008 2:49 am

...It seems I have read before that some UV tint in auto glass can absorb _some_ freqs, but I am not sure about 2.4 Ghz. The plan is to have them fed to one card, and then still use omni for second card, when i have the opportunity.

My average driving is rural and medium size towns, about zero skyscrapers or anything over a few stories tall. Thoughts?
On the tint issue, the concern is if you have a metallic based vehicle tint. This would attenuate the received signal greatly if not block it all together. The remarks you saw were probably related to glass mount cellular antennas where the problem first came to light (pun probably intended). If it is factory tint, the dealer can probably find out. For an after market tint it may be a tossup. If your side windows are on a door, or on an operable window you may be able to arrange a test. While stationary measure the strength of an AP with the tinted area not blocking the receiver. then leaving the receiver in the same place move the tinted area back in. If you see a major drop you have the metallic. You should be able to do that with any antenna even the notebook one.

On the antenna, if you feed a mini card with two antenna connectors you should be fine. I have used co-phased antenna harnesses, but only below 30mhz. I have no idea how those will perform at ghz frequencies where making sure the feed lines are exactly the same electrical length would be much harder. Also you would need to make sure there are no right angle connections, or something could fry because of the signal reflections. Of course if you can guarantee that nothing will transmit on the antenna you could use a coat hanger, or even tap the van itself to be your antenna.
The only reasons you need a tuned antenna are for transmit, or if you are trying for gain in a particular direction.

I had not thought to tap the vehicle skin until now. I wonder if there is a way to inhibit transmit completely on a card by cutting out a circuit or if things are too integrated at this point to pull off that kind of hack. Of course, most cars are not made of metal anymore either.

Postby dagaroth » Tue Aug 05, 2008 1:51 pm

I'm running debian linux on an old IBM i series laptop. I have it configured to boot right into kismet (I followed a few tutorials here)

Doing that brings the card right up into sniffer mode, the TX side never even comes on. I'd imagine that if you were to tap the antenna into the skin on a few panels you could do it that way. The problem is, not all the panels are electrically connected, so you may not get that good of a result.

Take a look at Whitedices setup. he has almost exactly what you're talking about, only more nuts.

IIR, he has 2 sectors on each side of his SUV, 2 facing out and frontwards, thru the side windows, and 2 others facing out and sideways through the back window. He also runs an omni with them, and IIR some random USB dongles as well.

My plan is to imitate him somewhat, with sectors on my small sidewindows, and when I have the spoiler taken off my Cobalt, 2 more sectors on the package tray. It's just a matter of spare cash ATM, and with gas being $4.40, and food/everything else going up because of it, spare, and cash are mutually exclusive.

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