[TriLUG] 2.4 Ghz signal distance issue - your thoughts?

[Jeff Groves]

Greg:

I too have been having trouble with my 802.11b network from time to time. 

I suppose what I've always heard from electrical engineering types is 
true.  Radio related stuff can be flaky as hell for the most odd reasons.

I'm no RF wiz, but the things that come to mind in your situation are:

1) too much gain on the signal
2) interference of some sort

The first issue (1) may be that you're pumping too much signal and 
causing trouble for the receiving side due to noise caused by 
overloading the receive side.  You might try pointing the two antennas a 
little off center and then compare performance.

For item 2), you could contact the local American Radio Relay League 
(ARRL) and see if they can do a check of the power level of your 
antennas and the surrounding area.  One of the more senior Hams in the 
group might be able to point you in the right direction that way.

I hope that I haven't exposed too much of my ignorance on the subject of 
RF by speaking up.  If I have, please let us know!

Thanks,

Jeff G.

Greg Brown wrote:

>All:
>
>I have a network on the Carolina Outer Banks.  I have one wireless
>link connecting two parts of the network toghether.  The distance
>between the two access points is roughly 300 yards.  The access points
>themselves are WRT54G units running OpenWRT, one in AP mode and one in
>WET mode (the device in WET mode connects, via cat5, to a Cisco 1200
>802.11b unit that the users connect to).
>
>Both OpenWRT boxes are connected to 14 Dbi Yagi antennas (antenex
>units).  The problem is the signal fades out, and on a regular basis
>which isolates the Cisco 1200 from the main network (and thus isolates
>the users who complain about this, loudly.   I have the antennas moved
>up about 15 feet into the air and they are pointed directly at each
>other.  They are both on the same channel, 8, and there are ZERO
>obstructions between the two antenanns.  I can put both into AP mode
>and I seem to get a strong enough signal from both so that they reach
>each other, but clearly something is amiss.
>
>I am thinking of swapping out the Yagis for 14 or 24 DBI
>omnidirectional antenans.  My hope is that the more focused signal
>will carry a greater distance thus providing a reliable link between
>the components of the network.  At best, when the current system is
>running, I can only link at 1 meg with much less throughput (for the
>RF overhead).  Ideally I'd like to connect at 5.5, and 11 meg would
>put me into a nirvana state.
>
>Has anyone deployed the same kind (sort-of) long-haul 802.11 link? 
>What kind of antenans did you use?  Does my next step sound like a
>good idea of throwing good money after bad?
>
>Greg
>  
>

-- 
Jeff Groves
email: jgroves at krenim.org             Web Site: http://www.krenim.org/