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

[john mitchell]

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
>  
>
Some thoughts on this:

1) 14 DB (per antenna) is PLENTY of gain. I do not think the problem is 
your antennas.
2) What type (and length(to nearest inch)) of coax are you using? "Low 
Loss" type?, an old Cable TV lead in? The length can be an important 
factor in a mismatched system! Are the connectors high quality and rain 
tite?
3) Did you adjust the RF transmit gain higher (to get better signal)? 
Are the recievers in overload?
  See Jeff Groves e-mail on this.
4) Does the signal fade at some specific time? And for how long does it 
fade out?
5) Are both WRTs in air conditioned rooms? Are they overheating?

john mitchell