[svlug] Wireless cards and distance and intervening walls etc

Richard Sharpe rsharpe at ns.aus.com
Sun Jul 14 16:22:02 PDT 2002

On Sun, 14 Jul 2002, Vince Duperron wrote:

> > 
> > Finally, are there any software tool I can use to check signal strength 
> > that the cards are seeing?

OK, it turns out that both the DLINK and SMC came with a Windows utility 
that showed signal strength and link quality in a nice GUI. Would be nice 
if such were available for Linux, but I can't take on any more projects 
> Hello;
> 802.11 uses a microwave signal to transmit data between stations.
> At the frequency it uses (about 2.4GHz) walls are semi-opaque.
> Opacity varies with material and thickness.  Some things to 
> keep in mind when operating at this frequency.  A wavelength 
> is about 12cm and a quarter wavelength is about 3cm.
> Movements of the transceiver about this much can mean the difference
> between good and bad signal.  Items about this large may interact strongly 
> with the signal.

Thanks for that info ... moving them both a little helped, and closing a 
closet door (about 3cm width) had a negative effect.

> You might try moving one, or both of the stations.  An external
> antenna might help, especially if the antenna has gain (a tiny 
> yagi-uda, for example).  Even a quarter wave antenna may be better
> than the antenna built into the card.  A quarter wave antenna is
> a piece of wire about 3.1cm long.  Ideally it would be placed
> above a metal plane (top of your computer case?)  You might try
> placing a 3.1cm long wire into the card antenna connector and
> see if it helps.  If the card is inside of your computer case,
> try removing the case and see if that helps.  A metal case
> would be very effective in blocking radiation from your
> transceiver.

OK, there are a number of sites that provide schematics and help in 
installing an external antenna jack. I might also investigate a DWL-520 or 
equiv if I can be sure my SiS730-based PCChips ML810 mobo has PCI 2.2.

> To measure the effect of your changes do:
> cat /proc/net/wireless
> Hope this helps
> Vince

Richard Sharpe, rsharpe at ns.aus.com, rsharpe at samba.org, 
sharpe at ethereal.com

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