[TriLUG] can't connect to wap when move it to alternate location

[Neil L. Little]

I read that channelizer will run in WINE. You are correct about the usb 
dongles. The low-end product is still $99 and a good prism/orinoco still 
costs only $65.

The 10w figure I was talking about for cellular is the cell tower. 
portables (what are now just called cell phones) only emit .6w maximum. 
They are stepped down in power by the cell tower.
A CDMA transmission sounds like regular static. It elevates the noise 
floor just a bit more. I was just trying to make the point that the 
likely hood of cell phones/base station interfering from fm capture, 
front-end blocking or adjacent channel is not likely.

Metal studs are used in office construction because though the price of 
the materials is a bit higher all you need are a pair of tin snips and a 
couple of self taping screws in the top and bottom plates. The extra 
materials cost is made up in labor savings.

A good Marconii IFR (1200) service monitor can be found between $1-3k. 
There are also several places in the triangle where they may even be rented.

Good Luck,

73,
Neil, WA4AZL


Joseph Mack NA3T wrote:
> On Sat, 3 Apr 2010, Neil L. Little wrote:
>
>> 1. 2.4 ghz does not have a lot of penetration in structures. Being an 
>> office building they no doubt use metal studding in the walls and such.
>
> didn't know the metal studing. Had assumed it was wood like a house 
> (so why is business metal, and houses wood?). Still there's a lot of 
> air between studs.
>
>> 2. Change channels. Go to the other side of the band. If there is 
>> interference from adjacent wifi this should clear it up.
>
> forgot to mention that I tried this and it didn't work.
>
>> 3. a is 5ghz, b&g is 2.5ghz, N can use either 5 or 2.5ghz but not at 
>> the same time.
>
> I though N was 5GHz, but was looking for an A wap to try out and the 
> specs say N/G. So I assumed N used G. Glad to know it can be A.
>
>> Cell phones use 800 - 850mhz and 1.9ghz. cdma and gsm use no more 
>> that 10w spread over a 1mhz bandwidth (spread spectrum has a 
>> threshold set at the noise floor).
>
> Cell phones are all over the place.
>
> 10w for a handheld device? 10w over 1MHz is a lot more power/bw than 
> 50mW/54MHz.
>
>> 4. Consider different types of antennas.
>
> yes am thinking that's the a next step. I'd rather have a good theory 
> as to the problem though first.
>
>> The type that come on waps are 1/4 wave at best (nice dummy loads try 
>> these sites: <http://www.radiolabs.com/>
>
> know them thanks
>
>> <http://www.l-com.com/content/hyperlinkbrand.html>).
>
> didn't know about them. thanks
>
>> There are also mesh networks.
>
> I've not used them, but if I can't connect to the wap, it doesn't 
> matter how the wap talks to the network.
>
>> 5. If you think that you have interference problems use a spectrum 
>> analyzer
>
> 5k$ for a nice HP ;-)
>
>> or channelizer (http://www.metageek.net/).
>
> had forgotten about them, since they were expensive (relative to a 
> pcmcia card at least) and non-linux. These are also only in-band 
> detectors. I can already see the other waps with `iwlist scan`, (and 
> from the debug info from wpa_supplicant) and there's only two other 
> waps in the vicinity. So I expect there's not much wifi around. I 
> expect the problem is not in-band wifi (although I don't have any 
> great ideas as to what it is).
>
>> 6. fire up a sniffer like net stumbler or kismet and see what other 
>> channels are doing.
>
> yes - this sounds like the next step. So far the wap has been plugged 
> into the wall and the network and hence immovable. I think I'll bring 
> a wap plugged into a UPS and carry them both around and try to just 
> associate with the wap (and not connect to a network on the other side 
> of the wap - just get a dhcp), and see where in the business area it 
> stops working.
>
>> Give this a try (Some good wifi info here) 
>> <http://www.smallnetbuilder.com/wireless/wireless-howto/24311-howtowlancollide> 
>>
>
> thanks.
>
> Joe
>