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Re: magnet mount antenna. possible WiFi?

From: Russell <>
Date: Fri, 03 Oct 2003 19:31:19 +0100

On Fri, 3 Oct 2003 10:38:36 -0700 (PDT), you wrote:

>I was at the goodwill and saw an antenna and I was
>wondering if it could be used for wifi. Its a radio
>shack magnetic mount antenna. I presume its used for a
>CB. The antenna its self is thin and has a coiled
>section in the middle and screws into the base. The
>base has a black cable comming off of it
>
>The antenna looks like this one
>http://www.wearcomp.org/steve5.jpg
>the one in picture D. I am thinking a head mounted
>antenna like the one in that pic would nice. But I
>don't know if the antenna I saw would work for WiFi.
>It might look a litte funny to have an antenna on your
>head, but if it extends the range of the WiFi its fine
>by me.=20
>
The coil and antenna length are probably suited to a particular
range of frequencies that are useless for 802.11b.
At 2.4Ghz a quarter wavelength antenna would only be 1.17in long.
http://www.csgnetwork.com/freqwavelengthcalc.html
I don't think you could use a CB or radio antenna. CB coax=20
has a 50 ohm impedance so you might get an impedance mismatch
between aerial and Wifi card and you risk damaging the Wifi card.

You might be able to detach one of the aerials from an access point,
attach a microax connector, and feed thin coax to where it's mounted,
or alternately get some design ideas from the O'Reilly Pringles can
project. http://www.oreillynet.com/cs/weblog/view/wlg/448

Most of the can/parabolic projects focus on extending distance=20
but they're directional which isn't what you want if you're roaming.
A better bet might be to look at increasing sensitivity and/or power
output, or increasing the number of Wifi bases.
I recently discovered that my Wifi Access point has SNMP tunable
parameters for the power output and the default isn't set at max.

Russell

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