[PLUG] Interference, was Preferred Routers, was Router Problem

Robert Eiffert reiffert at gmail.com
Thu Jan 31 19:24:21 UTC 2008


We had similar problems in our cul-de-sac with a NetGear music player
getting bumped off all too easily (seems to be an issue with that piece of
gear).  We tried different channels, but reception for internet radio was
getting dropped all too frequently.

What worked better was putting one of those paper/aluminum foil reflectors
on the  Music player box, pointing to the router.
http://www.freeantennas.com/projects/template2/index.html

Ultimately we went with a powerline ethernet adaptor as streaming was too
erratic for our ripped music.  But the antenna eliminated ~80% of the radio
station drops or disconnects.

We also moved the router further away from the front of the house and cable
modem.

The netgear box sensed 3-5 networks almost any day.

Robert

On 31 Jan 2008 09:39:41 -0800, Russell Senior <russell at personaltelco.net>
wrote:

> >>>>> "kurt" == kurt braget <joehaircut at gmail.com> writes:
>
> kurt> One weird thing about wireless in my area: if metro-fi goes
> kurt> down, everything else seems to go down. I've tested this several
> kurt> times with 4 separate laptops, on several different
> kurt> occasions. This is probably a separate topic, but here is a
> kurt> scenario: I check the AP's on 2 - 4 different laptops, Metro-fi
> kurt> and Metro-fi premium are up. Metro-fi goes down, and new AP's
> kurt> become visible (confirmed on multiple laptops). Right now, for
> kurt> example, Metro-fi and Metro-fi premium are up (which are
> kurt> apparently the same AP). If I connect to Metro-fi, eventually it
> kurt> will go down, then 2 - 4 new access points will go up, in
> kurt> addition to Metro-fi, yet, Metro-fi will not deliver
> kurt> internet. Moral of the story is, maybe there is some frequency
> kurt> issue going on in my area, but I'm not sure how to test for that
> kurt> (really want to learn though, so point me to a reference or
> kurt> tool-set if you know of one). If there is a frequency issue, I
> kurt> may not need a new router. I would like to try a Linksys though,
> kurt> as I've never had any trouble with them.
>
> That sounds a lot like an interference problem.  There are only three
> non-overlapping channels: 1, 6, and 11.  That means the some (though
> not much) of the power transmitted on channel 1 will be audible on
> channel 5.  Naturally, the closer you are to the transmit channel, the
> more this cross-channel interference you'll hear.  That fact pushes
> most, but not all people on to 1, 6 and 11.  Some people operate on 3
> or 9 or some other channel because it lets them hear their own AP
> better amongst the noise, while generating noise for two of their
> neighboring "non-overlapping" channels.
>
> As for checking for interference, my first knee-jerk suggestion is
> kismet.  It will show you which APs are present on which channels, and
> also which ones are audibly active from your location.
>
> Kismet[1] (properly configured) will show you 802.11 traffic.  There
> are other users of 2.4GHz spectrum though.  Like, lots.  There are
> cordless phones, microwaves, bluetooth, etc, etc.  One tool that
> purports to provide information on all of that is something called a
> wi-spy[2].  It is a small USB dongle and software that will generate a
> plot of rf energy by frequency across the unlicensed 2.4 GHz band.
> Personal Telco has talked about buying one of these at various times,
> but hasn't.  Partly because one of our members has one already and
> we've been able to borrow it in a pinch.  But, having to borrow it,
> means that it isn't readily at hand, and we've got to have sufficient
> "activation energy"[3] to follow through on it.  They used to be
> reasonably cheap (around $100), but recently about doubled in price.
> You can get one with a detachable antenna for about $400 now.
>
> [1] http://en.wikipedia.org/wiki/Kismet_%28software%29
> [2] http://www.metageek.net/products/wi-spy24x
> [3] http://en.wikipedia.org/wiki/Activation_energy
>
>
> --
> Russell Senior, Secretary
> russell at personaltelco.net
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>



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