Need Automotive WiFi Repeater for Automatic Roaming - to extend range of laptop with no antenna connector

Posted on 2006-05-18
Last Modified: 2013-11-09
I am about to embark on a tornado chasing adventure in the US heartland. I have a Dell laptop with internal WiFi only. I need to be able to detect and operate with WiFi AP's by using a good external antenna, but without physically attaching the antenna cable to the laptop.

Thus I want ithe ability to use a black box to repeat communications between my laptop's internal card and ANY network I run across - i.e. a repeater, but with special characteristics. From a functional standpoint, the solution would be invisible to the laptop - it would see the same network universe as it sees now but with better coverage - and would then be able to connect to one I choose. Being required to configure the digital 802.11 repeater before I could even see a network would probably not be acceptable.

There are three reasons for not wanting the physical connection:
  1) There is no antenna connector on the laptop - I would have to use one of my PCMCIA slots with another adapter
      card to even be able to do this.
  2) Microwave connectors of the size for this applicaiton are very fragile, and I have already broken one in cell phone use.
  3) The fewer physical connections to the laptop, the better. It needs to be able to quickly go from car to, let's say, truck stop restaurant and back without disconnecting and connecting a myriad of cables. Note that a repeater in such a situation would also give me extended coverage from anywhere near my car, such as a restaurant.

Approaches I have thought about that might be acceptable if certain conditions are met:

1) Get a commercial digital WiFi repeater and configure it for the roaming capability. I know there are repeaters, or AP's or routers that can be configured as repeaters. I DON'T KNOW if they have to be configured to a network before they can repeat it.

2) Use an "open" WiFi router such as the 54G and hack it to do this. I don't really have time for much hacking (although I have written considerable low level network code in the past), but if someone knows of an existing hack that would do the job.

3)Make a digital repeater from a second computer, with two WiFi cards and appropriate software or configuraiton. I have seen discussion of bridging using XP, but don't know if it will meet my roaming requirements. This has cost considerations and still might not meet my roaming requirements.

4)Use a two-way RF amplifier with a gain antenna on the roof and a little antenna in the car. An iin-car two-way amplifier (from Wilson) might relay the raw RF signals between the in-car environment and a high gain rooftop antenna. However, I don't know if they cover the  2.4 GHz band, and they also have problems with weak signal areas. These things do exist for cell/PCS phones, which is how I found them. Technically, the weak signal area problem is because two-way amplifiers are inherently limited by the near proximity of the amplifier antenna and the device inside the car - they tend to be more appropriate for situations where the signal is at least moderately strong outside the vehicle but weak inside - attenuated by the lousy antenna on the phone or WiFi card and the metal parts of the car body. In general, a digital repeater (options 1-3) would have probably significantly better range than the 2-way RF amp approach.

5) ??? Any other ideas?
Question by:gustnado
    LVL 1

    Accepted Solution

    I think you're on the right track with the bi-directional amp. By using a repeater you will have to configure a new parent router (the router you're repeating) everytime you go somewhere new. I've found that for most mobile wireless setups, a marine wi-fi amplifier kit works well, and considering your going to be chasing storms the anti-corrosion properties of the kit will come in useful. There's one kit in particular, sold by Sharper Concepts ( ) that comes with a 500mW amp and exterior omni antenna. Make sure you also get mounting harware and a DC-AC Inverter. This does include an additional PCMCIA card that hooks in with a RP-TNC connection to the antenna. Once mounted in the car it should increase your usable wireless range by 40-50%.

    Author Comment


    That opens up a line of possibilities that I hadn't considered. If someone doesn't give me a better solution, you win the points. If they do, you probably earn a split of them anyway.


    LVL 44

    Expert Comment

    "repeat communications between my laptop's internal card and ANY network I run across"

    You will NOT get this ever.  ANY network is a pipe dream you are imagining.  At best you can hope to hack into a network that is the same frequency, same channel, same encryption as yours.  Also if you are chasing electrical storms, you will have almost 0 chance of getting onto other network from inionized static.  Are you sure you have not been watching too many twister movies?  Their laptop interconnectivity is pure BS, you realize?

    You wont like this realistic approach, and probably wont consider it right.  So do a trial run down a road in rural OK before you decide, and at 60 MPH, see what networks you can connect to.  When you come up with 0.00 networks, come back to the sober reality that this will not work in normal let alone hi-static conditions.

    Author Comment

    I'm sorry, but part of what you are saying is nonsense. As an RF engineer (among other things), I know that electrical storms will have minimal effect on propagation at 2.5 GHz. The RF spectrum of lightning is strongly biased towards much lower frequencies.

    And no, I have been chasing tornados long before Twister came out (although a friend of mine was the technical advisor on the movie)..

    I have no expectation of connectiing to WiFi while going 50. I'll have EVDO for that, but it has spotty coverage. I have indeed used WiFi from the car in the midwest - a whole lot last year, but obviously not while moving, since WiFi (as opposed to WiMax) has very short range.

    My interest is in simply extening the range of my WiFi capability, preferably without adding a new card and antenna connector to my laptoip.

    Furthermore, were I to want to use a particular network, I wcould use the wardriving program to get the specifics, and then program an off-the-shelf repeater to work with it (just like I have joined various networks using my Laptop after detecting them with that program or even XP).

    I think you owe me points, not the other way around!

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