[GreenKeys] Wiping out your neighbor's reception

[John Foust]

At 02:43 PM 4/20/2005, Tim McNerney wrote:
>The modern equivalent wiping out your neighbor's TV reception,
>I'm sad to say, can be perpetrated by anyone.  Since the 2.4GHz
>ISM band is unlicensed, and the FCC is too busy catering to
>corporate BOPL interests seemingly intent on wiping out ham
>reception (oops, that's a rant for another day), all your neighbor
>has to do is to buy a cheap cordless phone, and he can wipe out
>your entire investment in 802.11b "WiFi" equipment.  And, though
>I could be mistaken, practically speaking, I don't think
>there is anything you can do about it, except maybe knock
>on all your neighbors' doors offering to buy them new phones.

WiFi is spread spectrum and that alone reduces the effects of
contention.  You also have a choice of 11 channels, three ranges 
of which are not overlapping.  Yes, other unlicensed equipment can
stomp on your signal, but you have a few options.  

As any ham knows, the simplest antenna can make a big difference.  
Even those rubber duckie antennas are 2 dB.  A little panel might 
be 6 dB.  Even using a seemingly highly directional 19 dB panel 
in the right spot in your house might do the trick.  There are plenty
of lobes that make it less directional than you think.  Access
points and laptop wireless cards are available in 30, 100 and 
200 mW varieties.  Don't expect the cheapest to work best.

>Actually, maybe you guys know...  What sort of equipment might
>one use to figure out which neighbor is the "perp"?

There are several sniffer programs for PCs or handhelds that
show signal strength in dB as measured by the wireless chipset.
NetStumbler is one.  Wander around until you find the right house.  

I'm a WISP, a wireless Internet provider.  My biggest problem in
the last year has been the 200 mW to 400 mW access point / routers
that SBC was giving away to DSL customers.  Many people didn't
even know they were radiating.  They are lighting up entire
neighborhoods all in the name of reducing tech support calls
because people would find null spots in their house at 30 or 100 mW.
Or they'd call to complain they couldn't use it in the backyard.

I even had a guy two doors down who had explicitly asked NOT to get 
the wireless router (for security purposes) yet they shipped him one, 
with a password set to his street address.  He didn't believe he was
stomping on my 100 mW / 15 dB broomstick until I showed him
the sniffer.  He was knocking out the neighborhood.

- John